Recirculating pump for instant hot water....

[Lamont Cranston]

Does anyone here have a recirculating pump to provide instant hot water to a faucet. I was looking putting at a heater under my kitchen sink, but decided it took more room than I was willing to give up. Then I started looking at the recirculating pumps, that use the cold water pipe as a return for the hot water that gets pumped to the faucet. If you don\'t know, a little description may be helpful. The common installation has a thermal valve at the last faucet of the plumbing run. This thermal valve is between the incoming hot water pipe and the incoming cold water pipe. The pump usually mounted at the water heater, pumps hot water through the hot pipe and back through the cold pipe until the thermal valve senses hot water at the last faucet at which time the valve closes so no more water circulates through the pipes. However the pump continues to run. Many of the pumps have a timer that controls at minimum a 15 minute on, 15 minute off cycle. You can also set it so the pump is off when sleeping or when you\'re not home if you have regular schedule.
What are your thoughts about automating this so that when the water reaches a certain temperature at the last sink it sends a signal back to the pump to shut it off. Wireless would be preferable. Because the thermal valve closes at about 90*F I suspect a electric water valve would be need to isolate the hot and cold water when the water has reached the proper temperature. Ditching the thermal valve. I\'m bothered by the pump running constantly when not needed. Even though it is only 22 watts. This is small compared to the cost of heating the water that cools in the pipe between the thermal valve cycles. This is somewhat offset by the
water/sewer cost and the cost to heat the extra water that is run down the drain. It wastes 1.4 gallons waiting for hot water at the shower, and about 1/2 gallon every time you try to get hot water at the kitchen sink. My water/sewer cost is 2.4 cent a gallon and another 3.2 cents to heat a gallon of water. Your thoughts?
Mikek

 

[Carlos E.R.]

On 2023-03-12 21:33, Lamont Cranston wrote:

Does anyone here have a recirculating pump to provide instant hot water to a faucet. I was looking putting at a heater under my kitchen sink, but decided it took more room than I was willing to give up. Then I started looking at the recirculating pumps, that use the cold water pipe as a return for the hot water that gets pumped to the faucet. If you don\'t know, a little description may be helpful. The common installation has a thermal valve at the last faucet of the plumbing run. This thermal valve is between the incoming hot water pipe and the incoming cold water pipe. The pump usually mounted at the water heater, pumps hot water through the hot pipe and back through the cold pipe until the thermal valve senses hot water at the last faucet at which time the valve closes so no more water circulates through the pipes. However the pump continues to run. Many of the pumps have a timer that controls at minimum a 15 minute on, 15 minute off cycle. You can also set it so the pump is off when sleeping or when you\'re not home if you have regular schedule.
What are your thoughts about automating this so that when the water reaches a certain temperature at the last sink it sends a signal back to the pump to shut it off. Wireless would be preferable. Because the thermal valve closes at about 90*F I suspect a electric water valve would be need to isolate the hot and cold water when the water has reached the proper temperature. Ditching the thermal valve. I\'m bothered by the pump running constantly when not needed. Even though it is only 22 watts. This is small compared to the cost of heating the water that cools in the pipe between the thermal valve cycles. This is somewhat offset by the
water/sewer cost and the cost to heat the extra water that is run down the drain. It wastes 1.4 gallons waiting for hot water at the shower, and about 1/2 gallon every time you try to get hot water at the kitchen sink. My water/sewer cost is 2.4 cent a gallon and another 3.2 cents to heat a gallon of water. Your thoughts?

Interesting idea. Never heard of this pump, but it certainly can solve a
problem. At worst, the thing can have a switch, and connected when going
to use the shower. Or a timer. Push the button, and have an hour of
instant hot water.

You might replace the thermo-valve with a sensor that would both switch
a valve and disconnect the pump. Or the pump could be installed at the
end of the run, perhaps, no valve.


In my case, the pump would need to put some pressure, because I have a
flash or instant gas heater. It fires when there is hot water flow, by
detecting a pressure drop, I guess.

--
Cheers, Carlos.

 

[Don Y]

On 3/12/2023 1:33 PM, Lamont Cranston wrote:

Does anyone here have a recirculating pump to provide instant hot water to a
faucet.

I think they covered this on (at least one) _This Old House_ episode, some
time back. IIRC, the situation was a second story bathroom that had \"slow\"
hot water... seldom used so any water \"stored\" in the pipe had ample time to
cool -- and a long lag to be \"flushed\" so fresh hot water could replace it.

I was looking putting at a heater under my kitchen sink, but decided it took
more room than I was willing to give up. Then I started looking at the
recirculating pumps, that use the cold water pipe as a return for the hot
water that gets pumped to the faucet. If you don\'t know, a little
description may be helpful. The common installation has a thermal valve at
the last faucet of the plumbing run. This thermal valve is between the
incoming hot water pipe and the incoming cold water pipe. The pump usually
mounted at the water heater, pumps hot water through the hot pipe and back
through the cold pipe until the thermal valve senses hot water at the last
faucet at which time the valve closes so no more water circulates through
the pipes. However the pump continues to run. Many of the pumps have a timer
that controls at minimum a 15 minute on, 15 minute off cycle. You can also
set it so the pump is off when sleeping or when you\'re not home if you have
regular schedule.

Is there any reason (other than simplicity of control) that the pump must
run in that way/duty-cycle?

What are your thoughts about automating this so that when the water reaches
a certain temperature at the last sink it sends a signal back to the pump to
shut it off. Wireless would be preferable. Because the thermal valve closes
at about 90*F I suspect a electric water valve would be need to isolate the
hot and cold water when the water has reached the proper temperature.

Could a pressure sensitive valve, instead, be used? Look at the pressures
encountered in each pipe in each use/recirculate case...

Ditching the thermal valve. I\'m bothered by the pump running constantly when
not needed. Even though it is only 22 watts. This is small compared to the
cost of heating the water that cools in the pipe between the thermal valve
cycles. This is somewhat offset by the water/sewer cost and the cost to heat
the extra water that is run down the drain. It wastes 1.4 gallons waiting
for hot water at the shower, and about 1/2 gallon every time you try to get
hot water at the kitchen sink. My water/sewer cost is 2.4 cent a gallon and
another 3.2 cents to heat a gallon of water. Your thoughts?

Does it truly have to be \"hot\"? E.g., could you mix in VERY HOT water
from an \"instant hot water\" dispenser at the use site? And, in this
way, keep the water \"warmer than cold\" -- until the real hot water
supply comes along to do the heavy lifting? ISTR these are relatively
small units designed just to deliver low volumes of very hot water
through a separate \"faucet\".

 

[Lamont Cranston]

On Sunday, March 12, 2023 at 4:17:11 PM UTC-5, Carlos E.R. wrote:

Interesting idea. Never heard of this pump, but it certainly can solve a
problem. At worst, the thing can have a switch, and connected when going
to use the shower. Or a timer. Push the button, and have an hour of
instant hot water.

You might replace the thermo-valve with a sensor that would both switch
a valve and disconnect the pump. Or the pump could be installed at the
end of the run, perhaps, no valve.


In my case, the pump would need to put some pressure, because I have a
flash or instant gas heater. It fires when there is hot water flow, by
detecting a pressure drop, I guess.

--
Cheers, Carlos.

Yes, I have seen the idea of a button at the sink, it does save the wasted water but not the time waiting for hot water.
It would probably be a longer wait because I suspect the pump has a lower flow rate than the normal outlet water flow.
It seems like the pump could have a pressure sensor on it to know when the thermovalve shut, but sense it is not a
displacement type pump, I don\'t have any idea if there is any or what the differential pressure is.
Mikek

 

[Ed Lee]

On Sunday, March 12, 2023 at 1:33:57 PM UTC-7, Lamont Cranston wrote:

Does anyone here have a recirculating pump to provide instant hot water to a faucet. I was looking putting at a heater under my kitchen sink, but decided it took more room than I was willing to give up. Then I started looking at the recirculating pumps, that use the cold water pipe as a return for the hot water that gets pumped to the faucet. If you don\'t know, a little description may be helpful. The common installation has a thermal valve at the last faucet of the plumbing run. This thermal valve is between the incoming hot water pipe and the incoming cold water pipe. The pump usually mounted at the water heater, pumps hot water through the hot pipe and back through the cold pipe until the thermal valve senses hot water at the last faucet at which time the valve closes so no more water circulates through the pipes. However the pump continues to run. Many of the pumps have a timer that controls at minimum a 15 minute on, 15 minute off cycle. You can also set it so the pump is off when sleeping or when you\'re not home if you have regular schedule.
What are your thoughts about automating this o that when the water reaches a certain temperature at the last sink it sends a signal back to the pump to shut it off. Wireless would be preferable. Because the thermal valve closes at about 90*F I suspect a electric water valve would be need to isolate the hot and cold water when the water has reached the proper temperature. Ditching the thermal valve. I\'m bothered by the pump running constantly when not needed. Even though it is only 22 watts. This is small compared to the cost of heating the water that cools in the pipe between the thermal valve cycles. This is somewhat offset by the
water/sewer cost and the cost to heat the extra water that is run down the drain. It wastes 1.4 gallons waiting for hot water at the shower, and about 1/2 gallon every time you try to get hot water at the kitchen sink. My water/sewer cost is 2.4 cent a gallon and another 3.2 cents to heat a gallon of water. Your thoughts?
Mikek

I had these pump before. So, a few observations: it only save money for gas water heater. Otherwise, it would be better to have electric heater closer to the faucel. The pump tends to lock up if not in use for long period of time. Suggestion is to run at least a few minutes per day.

Regarding cold water pipe recirculation, you would have to be careful about drinking from tap water. Hot water have more bacteria. You don\'t want to mix up hot and cold pipes.

 

[Lamont Cranston]

On Sunday, March 12, 2023 at 4:43:08 PM UTC-5, Don Y wrote:

Could a pressure sensitive valve, instead, be used? Look at the pressures
encountered in each pipe in each use/recirculate case...

I mentioned that, open endedly in my previous post because I don\'t know what the pressures would be.
You have a pump that is already at 50 psi at the input and it may have slight increase to make the water flow,
but I don\'t think is is much pressure

Does it truly have to be \"hot\"? E.g., could you mix in VERY HOT water
from an \"instant hot water\" dispenser at the use site?

Ya, I\'m already not to happy the the thermal valve works at 90*F so the water is already not hot.
I think that is a tradeoff so as to reduce the cost of the wasted heat lost in the pipes.

And, in this way, keep the water \"warmer than cold\" -- until the real hot water
supply comes along to do the heavy lifting? ISTR these are relatively
small units designed just to deliver low volumes of very hot water
through a separate \"faucet\".

I understand the idea, just not sure about a point of use water heater and a circulation pump.

 

[John Larkin]

On Sun, 12 Mar 2023 14:42:52 -0700, Don Y
<blockedofcourse@foo.invalid> wrote:

On 3/12/2023 1:33 PM, Lamont Cranston wrote:
Does anyone here have a recirculating pump to provide instant hot water to a
faucet.

I think they covered this on (at least one) _This Old House_ episode, some
time back. IIRC, the situation was a second story bathroom that had \"slow\"
hot water... seldom used so any water \"stored\" in the pipe had ample time to
cool -- and a long lag to be \"flushed\" so fresh hot water could replace it.

I was looking putting at a heater under my kitchen sink, but decided it took
more room than I was willing to give up. Then I started looking at the
recirculating pumps, that use the cold water pipe as a return for the hot
water that gets pumped to the faucet. If you don\'t know, a little
description may be helpful. The common installation has a thermal valve at
the last faucet of the plumbing run. This thermal valve is between the
incoming hot water pipe and the incoming cold water pipe. The pump usually
mounted at the water heater, pumps hot water through the hot pipe and back
through the cold pipe until the thermal valve senses hot water at the last
faucet at which time the valve closes so no more water circulates through
the pipes. However the pump continues to run. Many of the pumps have a timer
that controls at minimum a 15 minute on, 15 minute off cycle. You can also
set it so the pump is off when sleeping or when you\'re not home if you have
regular schedule.

Is there any reason (other than simplicity of control) that the pump must
run in that way/duty-cycle?

What are your thoughts about automating this so that when the water reaches
a certain temperature at the last sink it sends a signal back to the pump to
shut it off. Wireless would be preferable. Because the thermal valve closes
at about 90*F I suspect a electric water valve would be need to isolate the
hot and cold water when the water has reached the proper temperature.

Could a pressure sensitive valve, instead, be used? Look at the pressures
encountered in each pipe in each use/recirculate case...

Ditching the thermal valve. I\'m bothered by the pump running constantly when
not needed. Even though it is only 22 watts. This is small compared to the
cost of heating the water that cools in the pipe between the thermal valve
cycles. This is somewhat offset by the water/sewer cost and the cost to heat
the extra water that is run down the drain. It wastes 1.4 gallons waiting
for hot water at the shower, and about 1/2 gallon every time you try to get
hot water at the kitchen sink. My water/sewer cost is 2.4 cent a gallon and
another 3.2 cents to heat a gallon of water. Your thoughts?

Eight cents per shower doesn\'t sound like a big problem to be solved.
A second shower, or showering with a friend, is free.

Does it truly have to be \"hot\"? E.g., could you mix in VERY HOT water
from an \"instant hot water\" dispenser at the use site? And, in this
way, keep the water \"warmer than cold\" -- until the real hot water
supply comes along to do the heavy lifting? ISTR these are relatively
small units designed just to deliver low volumes of very hot water
through a separate \"faucet\".

Just run them in series, local electric water heater with a small
tank, fed from the long slow pipe from the main water heater.

We keep a bucket in the shower and run the water into that until it
gets hot. We water plants from the bucket. That takes maybe 2 gallons.

 

[Lamont Cranston]

On Sunday, March 12, 2023 at 4:47:23 PM UTC-5, Ed Lee wrote:

> I had these pump before. So, a few observations: it only save money for gas water heater.
Why would it only save money for a gas water heater? Second, I\'m not sure it ever saves any money,
as I think the extra cost to heat water that just cools in the pipe many times per day is higher that the money saved
on less water wasted down the drain.
Otherwise, it would be better to have electric heater closer to the faucet. The pump tends to lock up if not in use for long period of time. Suggestion is to run at least a few minutes per day.

Regarding cold water pipe recirculation, you would have to be careful about drinking from tap water. Hot water have more bacteria. You don\'t want to mix up hot and cold pipes.

Hmm, I have not seen any discussion about bacteria on the many pages of info I have read. This is the way these pumps are used, generally only on new installations is a separate return pipe used. Years ago we built a house with the water heater in the basement, I did add a return line and the whole thing was gravity fed so no pump needed, it worked very well.
Here is a somewhat typical pump although this has the extra bells and whistles like a timer and the thermal valve.
https://www.amazon.com/Watts-500800-Instant-Recirculating-Install/dp/B000E78XHG/ref=sr_1_5?keywords=Watts+recirculation+pump&qid=1678658313&sr=8-5
Mikek

 

[John Larkin]

On Sun, 12 Mar 2023 14:47:19 -0700 (PDT), Ed Lee
<edward.ming.lee@gmail.com> wrote:

On Sunday, March 12, 2023 at 1:33:57?PM UTC-7, Lamont Cranston wrote:
Does anyone here have a recirculating pump to provide instant hot water to a faucet. I was looking putting at a heater under my kitchen sink, but decided it took more room than I was willing to give up. Then I started looking at the recirculating pumps, that use the cold water pipe as a return for the hot water that gets pumped to the faucet. If you don\'t know, a little description may be helpful. The common installation has a thermal valve at the last faucet of the plumbing run. This thermal valve is between the incoming hot water pipe and the incoming cold water pipe. The pump usually mounted at the water heater, pumps hot water through the hot pipe and back through the cold pipe until the thermal valve senses hot water at the last faucet at which time the valve closes so no more water circulates through the pipes. However the pump continues to run. Many of the pumps have a timer that controls at minimum a 15 minute on, 15 minute off cycle. You can also set it so the pump is off
when sleeping or when you\'re not home if you have regular schedule.
What are your thoughts about automating this o that when the water reaches a certain temperature at the last sink it sends a signal back to the pump to shut it off. Wireless would be preferable. Because the thermal valve closes at about 90*F I suspect a electric water valve would be need to isolate the hot and cold water when the water has reached the proper temperature. Ditching the thermal valve. I\'m bothered by the pump running constantly when not needed. Even though it is only 22 watts. This is small compared to the cost of heating the water that cools in the pipe between the thermal valve cycles. This is somewhat offset by the
water/sewer cost and the cost to heat the extra water that is run down the drain. It wastes 1.4 gallons waiting for hot water at the shower, and about 1/2 gallon every time you try to get hot water at the kitchen sink. My water/sewer cost is 2.4 cent a gallon and another 3.2 cents to heat a gallon of water. Your thoughts?
Mikek

I had these pump before. So, a few observations: it only save money for gas water heater. Otherwise, it would be better to have electric heater closer to the faucel. The pump tends to lock up if not in use for long period of time. Suggestion is to run at least a few minutes per day.

Regarding cold water pipe recirculation, you would have to be careful about drinking from tap water. Hot water have more bacteria. You don\'t want to mix up hot and cold pipes.

I considered using waste water to preheat the cold water coming into
the water heater. There are gadgets to do that, and our incoming water
is always cold. But it would be a hassle with decades to pay back.

 

[Lamont Cranston]

On Sunday, March 12, 2023 at 5:03:21 PM UTC-5, John Larkin wrote:

Eight cents per shower doesn\'t sound like a big problem to be solved.
A second shower, or showering with a friend, is free.

It\'s not a big problem, and it all started with just wanting instant hot water at the kitchen sink,
finding not enough room under the sink and then reading about recirculation pumps and the thermal valve
then finding they are often installed at the farthest sink. Now I\'ve expended my thinking to the
whole house instead of just the kitchen sink. Although I may just drop back to the kitchen sink.

We keep a bucket in the shower and run the water into that until it
gets hot. We water plants from the bucket. That takes maybe 2 gallons.

Ya, that\'s something my wife would do, but I\'m not about to fill a bucket until the water is
warm then set the bucket out into the bathroom and take my shower, then worry about watering the plants.
But, I\'m not in CA. either, with all your states rules.
Mikek

 

[Carlos E.R.]

On 2023-03-12 22:43, Lamont Cranston wrote:

On Sunday, March 12, 2023 at 4:17:11 PM UTC-5, Carlos E.R. wrote:

Interesting idea. Never heard of this pump, but it certainly can solve a
problem. At worst, the thing can have a switch, and connected when going
to use the shower. Or a timer. Push the button, and have an hour of
instant hot water.

You might replace the thermo-valve with a sensor that would both switch
a valve and disconnect the pump. Or the pump could be installed at the
end of the run, perhaps, no valve.


In my case, the pump would need to put some pressure, because I have a
flash or instant gas heater. It fires when there is hot water flow, by
detecting a pressure drop, I guess.

Yes, I have seen the idea of a button at the sink, it does save the wasted water but not the time waiting for hot water.
It would probably be a longer wait because I suspect the pump has a lower flow rate than the normal outlet water flow.
It seems like the pump could have a pressure sensor on it to know when the thermovalve shut, but sense it is not a
displacement type pump, I don\'t have any idea if there is any or what the differential pressure is.

I need it to have the same flow of water as the tap. If the flow is too
small, the boiler doesn\'t fire. If it is different, the temperature
differs from the normal status. For example, if the flow is small, but
enough to trigger the boiler, say half of the normal tap flow, I would
get double the temperature for a while.

The button idea is to have the system active for a time, say one hour,
then it goes off. My pipes are not insulated, so I would waste too much
having the system waiting and ready the whole day.



--
Cheers, Carlos.

 

[John Larkin]

On Sun, 12 Mar 2023 15:19:11 -0700 (PDT), Lamont Cranston
<amdx62@gmail.com> wrote:

On Sunday, March 12, 2023 at 5:03:21?PM UTC-5, John Larkin wrote:

Eight cents per shower doesn\'t sound like a big problem to be solved.
A second shower, or showering with a friend, is free.
It\'s not a big problem, and it all started with just wanting instant hot water at the kitchen sink,
finding not enough room under the sink and then reading about recirculation pumps and the thermal valve
then finding they are often installed at the farthest sink. Now I\'ve expended my thinking to the
whole house instead of just the kitchen sink. Although I may just drop back to the kitchen sink.

Recirculation will waste heat. Some of the heat from hot pipes will go
outdoors and some will diffuse indoors, good in winter but bad in
summer.

We keep a bucket in the shower and run the water into that until it
gets hot. We water plants from the bucket. That takes maybe 2 gallons.

Ya, that\'s something my wife would do, but I\'m not about to fill a bucket until the water is
warm then set the bucket out into the bathroom and take my shower, then worry about watering the plants.

My wife is the plant person here. All I do is run the shower into the
bucket. I was waiting around anyhow.

But, I\'m not in CA. either, with all your states rules.
Mikek

No state rules apply to the bucket.

 

[Ricky]

On Sunday, March 12, 2023 at 4:33:57 PM UTC-4, Lamont Cranston wrote:

Does anyone here have a recirculating pump to provide instant hot water to a faucet. I was looking putting at a heater under my kitchen sink, but decided it took more room than I was willing to give up. Then I started looking at the recirculating pumps, that use the cold water pipe as a return for the hot water that gets pumped to the faucet. If you don\'t know, a little description may be helpful. The common installation has a thermal valve at the last faucet of the plumbing run. This thermal valve is between the incoming hot water pipe and the incoming cold water pipe. The pump usually mounted at the water heater, pumps hot water through the hot pipe and back through the cold pipe until the thermal valve senses hot water at the last faucet at which time the valve closes so no more water circulates through the pipes. However the pump continues to run. Many of the pumps have a timer that controls at minimum a 15 minute on, 15 minute off cycle. You can also set it so the pump is off when sleeping or when you\'re not home if you have regular schedule.
What are your thoughts about automating this so that when the water reaches a certain temperature at the last sink it sends a signal back to the pump to shut it off. Wireless would be preferable. Because the thermal valve closes at about 90*F I suspect a electric water valve would be need to isolate the hot and cold water when the water has reached the proper temperature.. Ditching the thermal valve. I\'m bothered by the pump running constantly when not needed. Even though it is only 22 watts. This is small compared to the cost of heating the water that cools in the pipe between the thermal valve cycles. This is somewhat offset by the
water/sewer cost and the cost to heat the extra water that is run down the drain. It wastes 1.4 gallons waiting for hot water at the shower, and about 1/2 gallon every time you try to get hot water at the kitchen sink. My water/sewer cost is 2.4 cent a gallon and another 3.2 cents to heat a gallon of water. Your thoughts?

Personally, I think this is not a good idea. It doesn\'t solve the problem of the hot water cooling in the pipe, in terms of the cost to heat it. In fact, it ramps up that cost by assuring there is constantly hot water that is losing heat.

In Puerto Rico, they actually seldom bother with hot water at sinks. You don\'t really need 130°F water to wash your hands. Some places use an instant hot water heater for the whole house. Those tend to not work so well, as the water cools significantly by the time it reaches the sink or shower. This may be because the pipes are run in the concrete walls or floors, which wicks away heat more rapidly than the air space in lumber and dryrock construction.

But they also use instant heaters at the point of use. These work well, if sized properly. 120V tends to be a bit less heat than you might like, but is generally good enough. One place had an instant hot water heater for the house, using gas. It seemed to cut in and out, with the water temperature going hot, then cold, every couple of minutes. Not much fun in the shower!

It is not uncommon for larger houses to have two hot water heaters, one for the main level, and one for upstairs. I have estimated my 30 year old hot water heater uses about 3 kWh per day, when no water is used. I get this from the whole house electrical use when no one is home. The normal level runs 0.384 kWh (reported units are multiples of 128 Wh/hr) and spikes up to around 0.896 kWh per hour once, every 4 hours. So that\'s about $0.35 per day, or $2.50 a week.

So how much would it cost to keep the water hot, in 50 feet of uninsulated copper pipe? I bet it doubles the cost of the hot water heater idle power. I think I\'d opt for good quality instant heaters, or install a second hot water heater (it can be a smaller unit and can be in the attic).

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

 

[Don Y]

On 3/12/2023 2:52 PM, Lamont Cranston wrote:

On Sunday, March 12, 2023 at 4:43:08 PM UTC-5, Don Y wrote:

Could a pressure sensitive valve, instead, be used? Look at the pressures
encountered in each pipe in each use/recirculate case...
I mentioned that, open endedly in my previous post because I don\'t know what the pressures would be.
You have a pump that is already at 50 psi at the input and it may have slight increase to make the water flow,
but I don\'t think is is much pressure

I\'m thinking about how the whole house pressure regulators work.
They drop the municipal water pressure to a point that the user
sets. But, if the internal pressure (on the house side) rises
above the municipal water pressure, a relief valve opens to
ensure the household pressure never rises above the municipal
water pressure.

[Folks who fail to install an expansion tank on the load side of
such a pressure reducing valve will experience very high pressures
when the water heater is depleted of hot water and that dense
COLD water must be heated. With no path back to the municipal
supply, the expanding water quickly drives the pressure in
the NOW CLOSED system very high!]

Does it truly have to be \"hot\"? E.g., could you mix in VERY HOT water
from an \"instant hot water\" dispenser at the use site?

Ya, I\'m already not to happy the the thermal valve works at 90*F so the water is already not hot.
I think that is a tradeoff so as to reduce the cost of the wasted heat lost in the pipes.

And, in this way, keep the water \"warmer than cold\" -- until the real hot water
supply comes along to do the heavy lifting? ISTR these are relatively
small units designed just to deliver low volumes of very hot water
through a separate \"faucet\".

I understand the idea, just not sure about a point of use water heater and a circulation pump.

I\'m saying to skip the pump. Let the \"conventional\" hot water delivery
mechanism move water to your point-of-use. *Know* that the first few
gallons of this will be \"tepid/cool\". Blend very hot water sourced
at the point of use to raise the temperature of that water -- until
the hot water from your \"real\" water heater can make its way through
the pipes.

I.e., rely on the fact that the \"instant hot water\" device can\'t deliver
a lot of water but can, hopefully, deliver enough to raise the
temperature of the water standing in the pipes. I *think* the way
those work is that they sense demand and only turn on (electric)
when the stored water (which is very little) temperature drops.

No idea what the overall power consumption would be as that would depend
on how often (and how *much*) you call on hot water.

 

[Carlos E.R.]

On 2023-03-13 00:48, Don Y wrote:

On 3/12/2023 2:52 PM, Lamont Cranston wrote:
On Sunday, March 12, 2023 at 4:43:08 PM UTC-5, Don Y wrote:

Could a pressure sensitive valve, instead, be used? Look at the
pressures
encountered in each pipe in each use/recirculate case...
   I mentioned that, open endedly in my previous post because I don\'t
know what the pressures would be.
  You have a pump that is already at 50 psi at the input and it may
have slight increase to make the water flow,
  but I don\'t think is is much pressure

I\'m thinking about how the whole house pressure regulators work.
They drop the municipal water pressure to a point that the user
sets.  But, if the internal pressure (on the house side) rises
above the municipal water pressure, a relief valve opens to
ensure the household pressure never rises above the municipal
water pressure.

[Folks who fail to install an expansion tank on the load side of
such a pressure reducing valve will experience very high pressures
when the water heater is depleted of hot water and that dense
COLD water must be heated.  With no path back to the municipal
supply, the expanding water quickly drives the pressure in
the NOW CLOSED system very high!]

Ah. That\'s because water can not flow back to the municipal pipes.

There is another method: the hot water tank has a portion of air at the
top of the tank. And, the tank itself has a little relief valve at the
bottom. Now I clearly see why.


Curio history.

At a flat owned by a friend of mine they had such a hot water tank. The
floor was number 7, I think. The municipal network only grants that the
water reaches the ground level, the building has a tank and a pump to
push the water up. A pressure group, they call that here. But these
pumps don\'t create a constant pressure, but oscillating between a high
and low levels, constantly. This means that a little bit of water was
entering my friends flat, and exiting, oscillating in an out, up to a
few times per minute (say four). And, the flat has a water meter, that
doesn\'t count the water going out.

Result was the flat got an invoice for many thousand litres a month, a
significant number of euros.

The called a profesional plumber, who took a long time to find \"the
leak\". Then he installed a one way valve.


--
Cheers, Carlos.

 

[Carlos E.R.]

On 2023-03-12 23:45, Ricky wrote:
> On Sunday, March 12, 2023 at 4:33:57 PM UTC-4, Lamont Cranston wrote:

....

> One place had an instant hot water heater for the house, using gas. It seemed to cut in and out, with the water temperature going hot, then cold, every couple of minutes. Not much fun in the shower!

I have that, it\'s very common here. The temperature is constant, as long
as you don\'t touch the hot water tap and the water flow is constant.

There are two types: cheap, there is a constant gas flow, so the less
water flow, the hotter it is. Expensive, there is an electronic
regulator changing the gas flow trying to keep the temperature constant.

--
Cheers, Carlos.

 

[Don Y]

On 3/12/2023 5:33 PM, Carlos E.R. wrote:

On 2023-03-13 00:48, Don Y wrote:
On 3/12/2023 2:52 PM, Lamont Cranston wrote:
On Sunday, March 12, 2023 at 4:43:08 PM UTC-5, Don Y wrote:

Could a pressure sensitive valve, instead, be used? Look at the pressures
encountered in each pipe in each use/recirculate case...
   I mentioned that, open endedly in my previous post because I don\'t know
what the pressures would be.
  You have a pump that is already at 50 psi at the input and it may have
slight increase to make the water flow,
  but I don\'t think is is much pressure

I\'m thinking about how the whole house pressure regulators work.
They drop the municipal water pressure to a point that the user
sets.  But, if the internal pressure (on the house side) rises
above the municipal water pressure, a relief valve opens to
ensure the household pressure never rises above the municipal
water pressure.

[Folks who fail to install an expansion tank on the load side of
such a pressure reducing valve will experience very high pressures
when the water heater is depleted of hot water and that dense
COLD water must be heated.  With no path back to the municipal
supply, the expanding water quickly drives the pressure in
the NOW CLOSED system very high!]

Ah. That\'s because water can not flow back to the municipal pipes.

Exactly. The pressure reducing valve blocks that path -- UNLESS it
has a builtin relief valve. \"Better\" valves have this as a standard
feature -- cuz so many folks DON\'T bother with the expansion tank
(in which case, why bother with the reducing valve?)

Our municipal pressure is ~110psi. Most \"appliances\" are rated at
a maximum of 80psi.

There is another method: the hot water tank has a portion of air at the top of
the tank. And, the tank itself has a little relief valve at the bottom. Now I
clearly see why.

I don\'t think the relief valve in the water heater \"wants\" to open
in all but extreme cases. I don\'t think it is designed for \"multiple
applications\".

Curio history.

At a flat owned by a friend of mine they had such a hot water tank. The floor
was number 7, I think. The municipal network only grants that the water reaches
the ground level, the building has a tank and a pump to push the water up. A
pressure group, they call that here. But these pumps don\'t create a constant
pressure, but oscillating between a high and low levels, constantly. This means
that a little bit of water was entering my friends flat, and exiting,
oscillating in an out, up to a few times per minute (say four). And, the flat
has a water meter, that doesn\'t count the water going out.

Result was the flat got an invoice for many thousand litres a month, a
significant number of euros.

Ha! Too funny.

The called a profesional plumber, who took a long time to find \"the leak\". Then
he installed a one way valve.

Ah, it\'s not common except for taller buildings (or, \"defective\" pumps?)
Otherwise, you would think the plumber would know what to look for...

 

[Don Y]

On 3/12/2023 2:52 PM, Lamont Cranston wrote:

And, in this way, keep the water \"warmer than cold\" -- until the real hot water
supply comes along to do the heavy lifting? ISTR these are relatively
small units designed just to deliver low volumes of very hot water
through a separate \"faucet\".

I understand the idea, just not sure about a point of use water heater and a circulation pump.

This:

<https://chilipeppersales.com/collections/frontpage/products/chilipepper-on-demand-hot-water-recirculating-pump-model-cp9000-b-version-wireless-wired>

implements your solution -- but at the point-of-use end of the line.

*If* you have (or can get) power, there, then I suspect it may be a
more adaptable approach to the problem. I.e., sense the temperature
at the point-of-use and use that to control the pump located *there*
(instead of trying to signal a pump located at the water heater).

A bit of tinkering might have you periodically running the pump
\"long enough\" to ensure the water at your sensor is representative
of the water queued up in the pipe. Or (welcome to the 21st
century) *learning* your usage patterns and anticipating your
future needs for hot water before you make those demands.

[Reactive solutions are so 20th century... :> ]

 

[Carlos E.R.]

On 2023-03-13 01:55, Don Y wrote:

On 3/12/2023 5:33 PM, Carlos E.R. wrote:
On 2023-03-13 00:48, Don Y wrote:
On 3/12/2023 2:52 PM, Lamont Cranston wrote:
On Sunday, March 12, 2023 at 4:43:08 PM UTC-5, Don Y wrote:

Could a pressure sensitive valve, instead, be used? Look at the
pressures
encountered in each pipe in each use/recirculate case...
   I mentioned that, open endedly in my previous post because I
don\'t know what the pressures would be.
  You have a pump that is already at 50 psi at the input and it may
have slight increase to make the water flow,
  but I don\'t think is is much pressure

I\'m thinking about how the whole house pressure regulators work.
They drop the municipal water pressure to a point that the user
sets.  But, if the internal pressure (on the house side) rises
above the municipal water pressure, a relief valve opens to
ensure the household pressure never rises above the municipal
water pressure.

[Folks who fail to install an expansion tank on the load side of
such a pressure reducing valve will experience very high pressures
when the water heater is depleted of hot water and that dense
COLD water must be heated.  With no path back to the municipal
supply, the expanding water quickly drives the pressure in
the NOW CLOSED system very high!]

Ah. That\'s because water can not flow back to the municipal pipes.

Exactly.  The pressure reducing valve blocks that path -- UNLESS it
has a builtin relief valve.  \"Better\" valves have this as a standard
feature -- cuz so many folks DON\'T bother with the expansion tank
(in which case, why bother with the reducing valve?)

Our municipal pressure is ~110psi.  Most \"appliances\" are rated at
a maximum of 80psi.

There is another method: the hot water tank has a portion of air at
the top of the tank. And, the tank itself has a little relief valve at
the bottom. Now I clearly see why.

I don\'t think the relief valve in the water heater \"wants\" to open
in all but extreme cases.  I don\'t think it is designed for \"multiple
applications\".

Oh, those I have seen can certainly be used often. Mine has a little
lever I can move with my finger and see water come out.

Curio history.

At a flat owned by a friend of mine they had such a hot water tank.
The floor was number 7, I think. The municipal network only grants
that the water reaches the ground level, the building has a tank and a
pump to push the water up. A pressure group, they call that here. But
these pumps don\'t create a constant pressure, but oscillating between
a high and low levels, constantly. This means that a little bit of
water was entering my friends flat, and exiting, oscillating in an
out, up to a few times per minute (say four). And, the flat has a
water meter, that doesn\'t count the water going out.

Result was the flat got an invoice for many thousand litres a month, a
significant number of euros.

Ha!  Too funny.

The called a profesional plumber, who took a long time to find \"the
leak\". Then he installed a one way valve.

Ah, it\'s not common except for taller buildings (or, \"defective\" pumps?)
Otherwise, you would think the plumber would know what to look for...

I guess that plumber now knows ;-)


That kind of pump (design from 1980) has a reservoir, typically a metal
sphere with an air filled rubber balloon inside. A pressure switch
connects the pump when pressure is low, disconnect when high. Thus, the
pressure oscillates.

I think there is a design that couples a pump and an inverter, running
continuously, that keeps a constant pressure. But runs non stop. If the
water flow will be constant, it is a good alternative.

--
Cheers, Carlos.

 

[Don Y]

On 3/13/2023 4:42 AM, Carlos E.R. wrote:

I don\'t think the relief valve in the water heater \"wants\" to open
in all but extreme cases.  I don\'t think it is designed for \"multiple
applications\".

Oh, those I have seen can certainly be used often. Mine has a little lever I
can move with my finger and see water come out.

Yes, I can do that, as well. But, I\'m not sure they are \"specified\"
with multiple uses in mind. It\'s (here) an *exception* for a water heater
to need to vent in that manner.

And, if it decides that was \"once too often\" and decides to fail, you
are (here) left without domestic water (unless you can isolate the
water heater from the cold inlet AND hot outlet connections).

Our (tank) water heaters also have a drain at the bottom. One
should periodically flush the tank to get rid of accumulating sediment.
But, the same hazard applies: if the valve decides that you\'ve
opened it one too many times and refuses to reseal, completely,
you\'ve got a persistent water leak.

That kind of pump (design from 1980) has a reservoir, typically a metal sphere
with an air filled rubber balloon inside. A pressure switch connects the pump
when pressure is low, disconnect when high. Thus, the pressure oscillates.

That\'s similar to how the expansion tanks are designed, here (though without
the switch/sensor). The tank (metal) is sealed. A bladder separates the
dry compartment from the wet. The user pressurizes the dry compartment
(with air) to reflect the nominal water pressure. Any increases in
pressure on the wet side (from the expansion of water as heated) force
the dry side to be compressed, providing more volume on the wet side.

I think there is a design that couples a pump and an inverter, running
continuously, that keeps a constant pressure. But runs non stop. If the water
flow will be constant, it is a good alternative.

It is interesting to see how different places approach these \"utilities\".
In parts of MX, water is *delivered* (via a truck) to a storage tank
mounted high on your residence (roof). Gravity feed so there\'s a limit
to the sort of pressure you expect.

And, more importantly, a limit to the amount of water you have available!
(I like REALLY long, hot showers so always decline invitations to visit
friends, there. \"Oh, you can bathe in the ocean and a sponge bath to remove
all of the SALT!\" NoThankYouVeryMuch. I left \"summer camp\" decades ago! :> )