# My hot water recirculation system is a disaster



## the_man (Aug 14, 2010)

there should be 2 check valves on the hot water recirc system. One on the recirc pipe and one on the cold inlet before any tees to the recirc pipe. my first thought is that you have a bad check valve or are missing one. the pump can create negative pressure, sucking cold water into the recirc line and eventually to the fixture being used


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## TheEplumber (Jul 20, 2010)

Recirc systems do work when properly plumbed. I suspect that your heater is too small for a 3400 SF house


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## Homerepairguy (Aug 1, 2010)

Michael Neill said:


> During the building stage I made the suggestion to insulate the hot water lines but I was told that this was not needed.


Seems to me that this is your problem. It's logical that in a hot water recirculation system both the hot lines to the fixtures and the return lines from the fixtures need to be insulated to prevent losing heat. In the perfect situation the water returning to the heater would be just as hot as when it left the heater. Of course this is not possible but insulating the to and from lines would work toward that goal.

I would insulate the entire hot water and return lines and then see what happens.

EDIT: To add to my reply, I think your uninsulated lines are working like a car's radiator. In an engine, heat is transferred to the water, then the hot water is sent to the radiator for cooling, then the return water to the engine is cooler. --- In your case, gas or electricity is heating the water in the water heater, then the hot water is sent to the long pipes (or tubing if PEX) which act as a car's radiator, and then the cooled water is returned to the heater. Your uninsulated system is working to cool the water in the heater.


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## Shane1 (Oct 12, 2010)

It sounds to me like the recirc system is incorrectly installed. Can you take some pics of what they installed and post them? Whats does the plumbing company say about this?


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## The Engineer (May 4, 2010)

Your main issue is the insulation like others have mentioned, A hot water recric system is typically designed for a 10 degree temperature drop, so for example, the water leaves the heater at 120 degrees, flow through the supply and return piping and should return to the heater at 110 degrees. Without any insulation on the hot water piping, and depending on the length of the loop, your probably getting return temperatures around 80 degrees. You should also have an aquastat on the return leg which controls the pump, so when the return temp reaches a set temperature, it shuts off the pump. Your pump is probably running 24/7 because the return temp is not getting up to the set point because of the heat loss from no insulation. Also, you could consider getting a timer to control the pump during specific hours during the day, so the pump only runs in the morning and in the evenings while people are home to help limit energy loss. All this depends on the size of the loop and the gpm of the pump. 

Also, you mention getting warm water out of the cold tap, that tells me you have hot water bleeding into the cold side somewhere close to the heater where the hot return and cold lines are piped back to the heater. There should be a check valve on the cold side before the hot return line ties in to prevent this, you should also have an expansion tank on the system because of the check valve.

If you could post a pic of the connections to the heater and the hot return/pump/valve configuration, that would help.


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## AllanJ (Nov 24, 2007)

Stirring of the water in the tank is not (should not be) a problem because for those folks without a recirculation system the same stirring of water occurs when you turn on a faucet and cold water enters (hopefully) at the bottom of the tank to replace the hot water being drawn.

If only one person is using hot water at a time, the square footage of the house doe snot matter.

Getting lukewarm water from the hot faucet too soon, and/or getting warm water from the cold faucet with the recirculating system running and not with the recirculation system valved off means the system needs some mods (like check valves).

Getting a few minutes of hot water followed by lukewarm water is not a pipe insulation problem. But you should still insulate the full lengths of the pipes to minimize heat loss into the spaces inside the walls where the pipes run.


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## Shane1 (Oct 12, 2010)

Here are some pics of what mine looks like for your comparison. It works like a champ, I have hot water at every faucet in under five seconds. Starting at the wall there is a ball valve, recirc pump, check valve, thermostat and then it tees off into the water heater and a drain spigot. That is also the flow of the water, from the house through the pump and back into the tank. I have no check valves on the top of the water heater only a ball valve on the inlet side. At this point insulating your pipes would probably pretty costly and labor intensive. I would make sure the system is plumbed right before anything else. Hope this helps and you get it all straightened out.


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## diditforme (Nov 3, 2010)

The need for a check valve seems clear. Is there a certain type, e.g., brass, or manufacturer that would be best? Are these valves OK with hot/warm water? My line is 3/4 in pex.


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## diditforme (Nov 3, 2010)

Just to tie up my question about the check valve for the hot water recirculation return line, I went to a plumbing supply store and was directed to a Campbell 3/4" check valve (CV-3T, $12).


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## jim45 (Sep 4, 2017)

My recirculation system works great on my home which is 3440 sq. ft. all on one level but with the water heater in the basement. I insisted the plumber insulate the hot and return lines and the first six feet of each fixture feeder hot line when we were building the house. Without the recirculation line working it takes almost two minutes to get the master bath shower warm enough to get into. During the summer I unplug the recirculation pump and gravity takes care of the recirculation (hot water rises to the fixtures in the living area above). It takes about three seconds to get warm water anywhere in the house. We also use the water heater to heat our home during the winter using an air handler. When it is running I need to turn on the recirculation pump to keep the recirculation line working since the air handler temperature drop messes up the gravity recirculation. My recirculation pump has a built-in, adjustable, thermostat so it turns off when the recirculation line is warm and I have a check valve in both the recirculation line and air handler. I also keep the pump on a timer so that we don't run it 24/7 during the winter--that saves energy. During the summer our propane usage drops to about 1 gallon per day and I think much of that is due to the recirculation line losses. I'm going to add some additional insulation to the hot and return lines this winter to try to cut that down some. It is costly to use recirculation but waiting two minutes for hot water daily is unacceptable, especially to my wife! Your plumber made a big mistake telling you the hot and return didn't need to be insulated and not making sure check valves were in place.


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## MTN REMODEL LLC (Sep 11, 2010)

the_man said:


> there should be 2 check valves on the hot water recirc system. One on the recirc pipe and one on the cold inlet before any tees to the recirc pipe. my first thought is that you have a bad check valve or are missing one. the pump can create negative pressure, sucking cold water into the recirc line and eventually to the fixture being used


Recirc lines/systems all somewhat differ and can be affected by your runs/elevations/drop/rise etc.

While we can not actually examine your system, feel the pipe temperatures as they are occuring etc.....

*I am almost certain that THE MAN above is dead correct
*

My next door neighbor had almost exact same issue with his recirc.... they would get in the shower to hot water.... and a few minutes later it got significantly cooler.

The check valve (only one on his system) was stuck open.... and the negative pressure of turning on the hot was backfeeding his cold line back into the shower.

(If a recirc line was not involved, I'd guess your issue might be the dip tube in your water heater.... as in principle you were wondering about in your initial post)

On my present home in southern Nevada, I have a recirc line.... but I don't want it running all the time... wasteing energy and additionally competeteing with my A/C. 

I put the Grundfaus pump on a remote control clicker plug in unit ($15 at HD or Lowes), so when my wife wants immediate hot for the WM or just at the kitchen faucet, she clicks in on 5 minutes before...... or if it a regular need, like showers in the morning, put the pump on a timer.

Good luck


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## Plumb69 (Dec 13, 2018)

I always put a check valve on cold inlet and also recirc line..never had a problem with 25 years of experience. Also if you have problems with new installation of fixtures suck as a touchless kitchen faucet you may need a check valve at the faucet location if you leave the handle on at your desired temp,when not in use there could be mixing..also any plumbing fixture that has a divertor after the hot and cold shut offs.


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## Nealtw (Jun 22, 2017)

After you have it figured out set it up with a smart switch so you can turn it on for the few minutes before a shower or what ever. I am sure the phone could be programmed to turn it off after how many minutes it needs to deliver the hot water.
Then you have saved the heat bill as well as the water bill.


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## MTN REMODEL LLC (Sep 11, 2010)

I have a grundfaus recirc pump, and plugged it into a $9 standard-stock remote control from HD or Lowes with an on/off switches.

Sits in the kitchen drawer and we turn it on/off as needed.


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## uhuknow (Aug 28, 2019)

This sounds a lot like some issues i am having with my system. Can the re-circulation pump also cause an increase in water pressure while the water heater is also heating? I have unplugged my re-circulation pump and have seen water pressures return to what i assume is normal 40psi-60psi (60psi when heating). VS 110 PSI when heating with recirc pump installed.


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## jim45 (Sep 4, 2017)

The recirculation pump is quite small and would not be able to pressurize the hot water line significantly. If you're seeing that sort of pressure increase the only thing I can think of that's associated with the recirc pump is that it is causing the water in the hot and return lines to heat up quite a bit when you turn it on from cold causing the water heater to run more to supply that heat. When water heats it expands and if there's no hot water being used that expansion could cause the pressure to go up dramatically since there's no air in the system to compress and water is not compressible. Typically there's a small expansion tank in the hot water system with an air bladder that absorbs the expanded water and keeps the pressure from rising much. My hot water expansion tank is only 1.5 gallons, I think, and I never see a pressure rise under any conditions. I insulate that tank to reduce the heat loss also. Check and see if you have an expansion tank connected to the hot water line. If not, I think that's the problem.


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## uhuknow (Aug 28, 2019)

Thanks for the quick response Jim. 

I do have an Expansion tank. I can't tell exactly where it lands in the system as the connection that comes to it is coming out of the wall. Since i have unplugged the recirc pump, and closed the valve that feeds to it i haven't had any build up of pressure. I was seeing the same issues that were talked about previously in this thread. Hot would output warm water at best, and occasionally cold water would spit out hot for the first 5-10 seconds. so far with the recirc unplugged just a long long wait for hot water can be upwards of 3-5 minutes of running water, but once hot water arrives it is HOT:devil3: 

Previously i thought my expansion tank wasn't properly charged, i had checked it and it seemed properly set.


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## CaptTom (Dec 31, 2017)

I've heard of people hooking them up to the bathroom light switch, or motion sensor, so they only start when someone enters the room. Presumably, they've done their thing by the time that person turns on the hot tap. Admittedly, I've never seen that arrangement, but it makes some sense.


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## jim45 (Sep 4, 2017)

Touch the bottom of the expansion tank to see if it is warm. If not, it may be on the cold side of a check valve feeding water into the water heater where it can't absorb the hot water expansion. An easy test to do is to leave a hot water faucet on very low and turn on the recirc pump. That will keep the pressure under control and verify that the increase in pressure was due to water heating. If the expansion tank is in the wrong place you may be able to add small one anywhere in the hot water line more easily than replumbing the existing one. The expansion of the water is very small but in a sealed system that can raise the pressure a lot. There is a pressure relief valve on every water heater that will open to let water out if the pressure gets too high. That may be what's limiting the pressure to 110 psi when the recirculation pump is on.


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## uhuknow (Aug 28, 2019)

Attached image is how things are setup. the tank doesnt seem warm or hot at any point, and so far since the recirc has been unplugged i havent seen pressure go above 65 psi. and no water has came out of the pressure relief valve on the hot water tank. (typically at least 5 gallons a week minimum).


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## hkstroud (Mar 17, 2011)

Assuming that you have had this system for sometime and that it has functioned properly and that no plumbing changes have been made..


You don't show the pressure regulating valve that you obviously must have. You don't show how close it is to the water heater. Feel the temperature of the output pipe of the pressure regulating valve when water heater is heating and the recirculating pump is running. Feel the temperature of the output pipe of the pressure regulating valve when water heater is operating and the recirculating pump is turned off.


I suspect that you will feel a significant difference. I suspect that a temperature difference is affecting your pressure regulating valve. It shouldn't of course, but a build up of mineral deposits may cause it to malfunction with changes in temperature.


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## jim45 (Sep 4, 2017)

I see what you mean about not being able to tell where the expansion tank is attached to the plumbing and from the photo I can't tell for sure how the recirc pump is installed in the system. Hkstroud mentioned a pressure regulating valve but, as far as I know, there typically aren't pressure regulating valves associated with hot water heaters. The only pressure regulator valves I'm aware of are part of the well pump control and another typically where the cold water from the well comes into the house. The temperature relief valve on the water heater is there to relieve pressure if the water heater control breaks and it stays on all the time causing the water to boil.

Here's how my system is plumbed. Cold water from the well comes goes through a shutoff valve and then a check valve and then into the cold water supply of the water heater. The check valve keeps hot water from going back into the cold water line when someone turns on a cold water faucet or flushes a toilet causing a pressure drop in the cold line. Then, the hot water pipe on the water heater goes to the expansion tank, through a shutoff valve and into the hot water supply for the rest of the house. The recirculation pump input comes from the hot water return line (a separate pipe typically connected to the hot water line at the point furthest away from the water heater). Both the hot water line and the return line should be insulated to conserve energy. The output of the recirc pump goes through a check valve and then into the cold water inlet of the water heater. My recirc pump has a temperature control that shuts it off when the water in the return is warm to conserve energy.

If the recirculation line is not in use the water in the return line will be cold. Then, if you turn on the recirculation line that cold water in it will go into the water heater and cause the water heater to turn on to heat it. That will cause thermal expansion in the system and unless there is an expansion tank it will raise the pressure.

Here's another thought. With your expansion tank mounted with the inlet up, if the bladder fails it will let the trapped air below the bladder to bubble up to the top where it will escape into the water pipes. After awhile all the air will be gone and the tank will be filled with water and it will have no ability to handle expansion. You can briefly touch the air valve on the bottom of the tank. If any water comes out, instead of air, the bladder has failed and the tank needs to be replaced. My tank is mounted with the inlet at the bottom so a failed bladder doesn't release the trapped air on the other side of the bladder.


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## hkstroud (Mar 17, 2011)

Sorry Jim, but you got it backwards. Pressure regulating valves are not associated with wells. With wells the pump switch controls the water pressure. Pressure regulating valves are associated with municipal water systems. They are often necessary, because in order to get enough water to every one the municipal system has to use a very high pressure. Too high for the residential user. The PRV reduces and regulates the residential users pressure. They are usually the first thing on the incoming water line to the house. Some PRVs have an integral check valve and some don't.


We can assume that uhuknow has a PRV and that it has an integral check valve. Otherwise he would not need the expansion tank. Without the check valve that is part of the PRV, a build up of pressure would simply move back up the line into the municipal water system.


If uhuknow were on a well, any check valves would be at the well pump or at the well head. Any build up of pressure created by the water heater would move back into and be absorbed by the well tank.


It is pretty obvious where the incoming cold water line is behind the drywall. It comes out of the drywall and goes to the water heater. The expansion tank tees into the cold water line above the water heater connection. We just don't know how close the PRV is. Is the PRV close enough for the use of the recirculating pump to cause an increase in water temperature at the PRV?


Recently my PRV began making an unusual noise. I ignored it as long as I could because I didn't want to change it out. Finally I loosened the lock nut around the adjustment screw. I turned the adjustment screw in several turns, returned it to its original position. I then turned it out several turns and returned it back to its original position. It now functions properly.


Apparently, I disturbed the build up of mineral deposits for the last 25 years. I can certainly see the logic of changes in water temperature affecting a build up of mineral deposits in a PRV if the PRV is close enough to the point where the recirculating pump tees into the incoming cold water line and causes hot water to move back up the line.


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## uhuknow (Aug 28, 2019)

What does a PRV look like?


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## hkstroud (Mar 17, 2011)

It will usually be the first thing on your cold water pipe to the house. If you live where it seldom freezes it may be out side but usually inside.


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## jim45 (Sep 4, 2017)

HKstroud, our well system does actually have a PRV where the water line goes into the house. It's not a traditional on/off well controller installed in most well systems. Instead, the well control has a pressure sensor that sends a signal to the control and it sends a signal over the pump power lines telling the pump to run faster or slower depending on the actual pressure desired. That way we don't see water pressure fluctuations in the house when sprinklers turn on and off. Since our Grundfos constant pressure well control can be set as high as 100 psi for irrigation purposes I didn't want the house to see over 60psi so the PRV essentially protects the house fixtures from high pressure.

If you're correct that the expansion tank is connected to the cold line and if there is a check valve in the cold line going into the water heater then I'm pretty sure thermal expansion of the heated water has nowhere to go but to increase the pressure until the water heater overpressure valve opens at 110deg. If the water heater was off for a long time and the water in it was cold, starting the water heater up without any hot water faucet being turned on would drive the hot water line pressure way up. I don't see any way that the small recirc pump could increase the system pressure just driving hot water around the recirculation loop.


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## hkstroud (Mar 17, 2011)

Use of a re-circulation pump would not increase the pressure. Its use could however cause an increase of water temperature back up the cold water line to the PRV. Please note the use of the word "could". Also please note my opening statement about the assumption that the system has been in use for some time, has functioned properly and no plumbing changes have been.
Concerns about the expansion tank do not logically fit. If it is defective, it is defective. The use of the re-circulation pump would not change its behavior.

Your use of a PRV is a logical and good solution for your situation but your situation is not the usual well system.

Certainly easy enough to feel the pipes when re-circulation pump is in use and when it is not. If there is no temperature difference then my thoughts don't apply. However, the PRV could still just be defective.

uhuknow could still do exactly what I did and it might make a difference if a build up of mineral deposits is affecting the PRV. Then again it might not.


If there is a check valve on the cold water input line between the water heater and the expansion tank it must be behind the drywall.


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## TheEplumber (Jul 20, 2010)

PRV on a municipal system is a pressure *reducing* valve
I believe a pressure *regulating* valve on a well controls pump frequency
Two different beasts.... so I think you both are right, just a terminology thingy.
@uhuknow have tested the pressure of the expansion tank? Have you pressed the 
valve stem to see if water comes out?


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## hkstroud (Mar 17, 2011)

> just a terminology thingy.


You could be right. I sometimes have that problem with the wifey thingey.


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