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No Hot Water or Lukewarm Water When Circulation Pump is Off

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Hello everyone. I am new here, and excuse me if this is a duplicate question. However, I can't find a matching answer for my issues.

I recently installed a Watts circulation pump. The sensor valve is located in the guest bathroom. It worked fine initially when I turned the timer off. I received hot water everywhere in a second. However, my gas bill doubled in the first month. I begin to use the timer on the circulation pump.

I noticed that I lose hot water when the pump is off. For example, I set the timer from 6:30 am to 12 pm and 5 pm to 10 pm. When I use water outside of the timeframe, I don't get hot water. The water in the master bathroom is lukewarm. Especially when you take a shower, the water gets colder and colder. The guest bathroom is lukewarm or cold too.

I know my water heater and circulation pump have no problem because I receive hot and cold water when the pump is on. I am unsure if this is something to do with the sensor valve. Possible other issues I am not aware of? I appreciate any help you may provide.

Comments

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,167
    edited January 2023
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    You may be missing a check valve. Who installed the pump? Where is the pump located (near the water heater or under one of the remote sinks). What model pump? Is there a dedicated return line to the water heater?

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    mattmia2
  • crystalzheng86
    crystalzheng86 Member Posts: 5
    edited January 2023
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    I did myself. I used whatever it come with the package. The instruction didn't say I need a check valve. (I am new to plumping). The pump is located on the top of water heater. The circulation pump is Watts Premier Instant Hot Water Recirculating Pump System with Built-In Timer 6" X 6", model is 500800. I don't know if there is return line (This is first time to deal with plumping/water heater). My water heater is A.O. Smith ProMax +.
    Thanks for your help
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,389
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    Hi, If I have it right, the pump pushes hot water from the tank into the piping, using the cold line as a return to the tank. So, you've tied into the cold line and when you turn on a hot tap, it seems water from the cold line is flowing to the tap in addition to the hot water from the tank. So, you get warm or cool water depending on the friction in each side of the plumbing. As Ed suggests, putting a check valve where you tied into the cold line will prevent the cold water from getting into the hot side. If there is a shutoff valve there, you could test this theory by closing the valve (with pump off) and running a hot tap. If it gets and stays, hot, you need a check valve.

    Yours, Larry
  • crystalzheng86
    crystalzheng86 Member Posts: 5
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    @Larry, thanks for your suggestion. I will turn off the shutoff valve and test it when I get home.

    Additional question, how do I know if I have return line? if I need to install a check valve, where do I install it?

    I get instant hot water everywhere if I don't use timer. However, my gas bill went from $80 without pump to $160 the first month I install the pump. other people from different site mentioned their gas bill only went up $10-$20 per month. Now I feel like my pump is not working/installed correctly.
  • mattmia2
    mattmia2 Member Posts: 9,959
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    if your piping isn't insulated it will cost a lot to run continuously.
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,389
    edited January 2023
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    Hi, It's easy to triple your water heating bill with a recirc pump running all the time. Basically you're increasing the heat loss by keeping plumbing hot. So, you want to run the pump as few hours a day as possible. If there is a way to activate it only when you know you're going to want hot water, that would be best.
    About a return line, water has to get back to the tank somehow, so there is a return line. If it isn't a separate, dedicated pipe, than it has to be the cold piping. I think your system has a crossover valve that gets installed under a sink. That is where you're connecting to the cold plumbing.... and where a check valve should go. ;)

    Yours, Larry

    ps. When looking for a check valve, get one that's designed to be quiet! I'd look for a spring check with a soft seat, so it doesn't rattle. Swing checks tend to be a maintenance problem, particularly in hard water.
  • crystalzheng86
    crystalzheng86 Member Posts: 5
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    @mattnua 2, I am not sure if my piping is insulated. I am assuming they are not because it took a long time to get hot water before I installed the circulation pump. but $80 more than my normal gas bill is way too much/abnormal. not sure how other's energy bill looks like.

    @Larry, thank you so much for all the information you have provided. Why the check valve need to be installed under the sink in my case? is it because it's Watts recirculation pump with crossover valve? I watched few videos and they were all installed next to the pump connected to the water heater
  • heathead
    heathead Member Posts: 234
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    Did you install a valve or something at a far sink. If you did that is creating the cross over to test this close the valve to this and turn off your circulation pump. See if you get your warm water back. If you installed something beside the pump that is your problem.
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,389
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    Hi @crystalzheng86 , You want to prevent any cold water from getting into the hot side piping, so installing a check valve where you tied into the cold water will prevent that possibility. Maybe a photo of the under-sink arrangement will help clear things up. B)

    Yours, Larry
  • crystalzheng86
    crystalzheng86 Member Posts: 5
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    I installed the sensor valve that came with the package under the sink. 
    I wonder if the sensor valve has problem. 
  • heathead
    heathead Member Posts: 234
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    Close on of the valves going to the valve and see if your problem goes away. Make sure you keep your pump off. If all is back to the way it was before installing the system the part is bad. It should have a valve in it that lets the hot water ffed back from cold water pipe to the water heater.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,167
    edited January 2023
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    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    Larry Weingarten
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,167
    edited January 2023
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    I had a bathroom that was added on to the home in what used to be the garage. It is now a spare bedroom for visiting grandchildren. That bathroom takes the longest time to get hot water to the tap, I had the great idea to install the recirc pump powered by the bathroom light switch. That way, when you went in to use the bathroom, the pump would start and by the time you were finished using the facility the hot water was there. When you left the room and turned off the light, the pump stopped operating. This worked well for us since all the other water taps were much closer to the water heater and the time lag from "open to hot" was not that long.

    Just an energy saving idea for a special circumstance

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    mattmia2heathead