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-   -   Grundfos hot water circulation pump water temperature problem (https://www.askmehelpdesk.com/showthread.php?t=743102)

  • Apr 7, 2013, 01:33 PM
    bills1260
    Grundfos hot water circulation pump water temperature problem
    I recently installed a new replacement Grundfos UP 15-29 SU/TLC hot water circulation pump at my home. It is in the hot water return at the bottom of the water heater, installed as before. Water heater is 5-years old.

    Problem is that the water runs hotter when the pump is off. In fact, it is only warm when pump is on. Pump runs OK and is silent, but curiously there is a sound from (in) the water heater when the pump is on. (Sort of a whooshing or "rrrrr" sound.) No sound when pump is off. Suggestions?
  • Apr 7, 2013, 09:43 PM
    hkstroud
    Quote:
    Problem is that the water runs hotter when the pump is off
    If that means that the water out of the faucet is hotter with the pump off, I suspect that you have the pump installed backwards. Instead of pulling the water out of the recirculation line and pumping it into the bottom of the heater, you are pulling the cold water out of the bottom of the tank and pumping it into the recirculation line.
  • Apr 8, 2013, 03:10 PM
    bills1260
    Quote:
    Originally Posted by hkstroud View Post
    If that means that the water out of the faucet is hotter with the pump off, I suspect that you have the pump installed backwards. Instead of pulling the water out of the recirculation line and pumping it into the bottom of the heater, you are pulling the cold water out of the bottom of the tank and pumping it into the recirculation line.


    Thanks. Sounds logical but I have checked it before and the arrow on the Grundfos pump points into the water heater from the hot water return line. It connects at the bottom water drain line of the heater.

    What may be relevant is that the water heater makes a sound when the pump is on, as I wrote. The sound is like a grumbling water agitation noise. Quite noticeable and not there when the pump is off. As I said, the water heater is only 5-years old and was professionally installed, including the old circulation pump.

    Another thing, I noted there is a check valve upstream from the pump, that is at the input side of the pump, not between the pump and the tank.

    When the pump is on it quickly delivers the “warm” water. It just never gets hot. Any more thoughts?
  • Apr 8, 2013, 04:21 PM
    Milo Dolezal
    Is there a check valve installed between the pump and water heater ? Also, Air Release valve should be installed in the same location. Bleed the pump well. If not bled it will run but never pull water. Back to you. Milo
  • Apr 8, 2013, 05:56 PM
    hkstroud
    Quote:
    there is a sound from (in) the water heater when the pump is on
    Is that all the time the pump is running or just when the pump is running and hot water is being used?
  • Apr 8, 2013, 06:13 PM
    bills1260
    Quote:
    Originally Posted by Milo Dolezal View Post
    Is there a check valve installed between the pump and water heater ? Also, Air Release valve should be installed in the same location. Bleed the pump well. If not bled it will run but never pull water. Back to you. Milo
    There is no check valve between pump and water heater. Only one is on input side of pump. Also no Air Release valve at that location. I will check the bleeding, but believe it was bled OK at installation.

    Over.
  • Apr 8, 2013, 06:16 PM
    hkstroud
    Repeat

    Quote:
    there is a sound from (in) the water heater when the pump is on
    Is that all the time the pump is running or just when the pump is running and hot water is being used?
  • Apr 8, 2013, 06:17 PM
    bills1260
    Quote:
    Originally Posted by hkstroud View Post
    Is that all the time the pump is running or just when the pump is running and hot water is being used?
    The sound is whenever the pump is on, hot water use or not. It is noticeable, and when I put my ear to the tank, it is very clear. Like maybe water rushing in the tank. Sound goes away instantly when pump is turned off.
  • Apr 8, 2013, 06:19 PM
    bills1260
    Quote:
    Originally Posted by bills1260 View Post
    The sound is whenever the pump is on, hot water use or not. It is noticeable, and when I put my ear to the tank, it is very clear. Like maybe water rushing in the tank. Sound goes away instantly when pump is turned off.
    By the way, thanks to both of you. For now I have turned the pump off. (It was installed about two months ago. Sound has been there from the beginning.)
  • Apr 8, 2013, 07:05 PM
    hkstroud
    Sound must be from water being pumped into tank. Did you increase the size of the pump?

    Doesn't explain getting only warm water when pump is running. Suggest replacing check valve.

    Here is my story.

    When I set up my recirculation line about 20 years ago, I ran recirculation line from master bath second floor to water heater in basement. I tied the recirculation line into water heater cold water input line, with pump and appropriate check valves. Worked fine for a number of years until pump quit.
    When pump quit I took out pump and reconnected the line. Fully intending to replace pump. During required period of procrastination of getting a new pump, I noticed that the system still worked. I had a gravity flow system.

    Everybody is happy for a number of years until wife kicked me out of the master bath and to the basement. Then after a few years she began complaining that if I showered in the basement while she was in the shower upstairs, she only got cold water. After waiting a few years to see if the complaining would stop, I decided that the check valve was faulty. She also recently began complaining that she got cold water if the guest bath was being used.

    A few weeks ago I replaced the check valve. Old valve was coated with mineral deposits. The new check stopped the "cold water" complaints. However, the circulation due to gravity flow had stopped. I pulled the new check valve and it was a little sticky on opening and the flow apparently wasn't enough to open it.

    Being cheap I didn't want to purchase a pump when I had had a gravity flow system that worked. Being lazy I didn't want to do the work repiping the recirculation line to the drain valve as a gravity system is supposed to be done.

    While I debated, I put on my plumbing ingenuity hat. I changed the check valve from horizontal to a 45 degree angle. That cause the swing valve to open slightly so that I get the gravity flow and the back pressure on the recirculation line when a faucet is opened is enough to causes it to close and prevent cold water from going up the recirculation line.

    Everybody is happy once again, for now.

    Replace that check valve.
  • Apr 9, 2013, 11:07 AM
    bills1260
    Quote:
    Originally Posted by hkstroud View Post
    Sound must be from water being pumped into tank. Did you increase the size of the pump?

    Doesn't explain getting only warm water when pump is running. Suggest replacing check valve.

    Here is my story.

    When I set up my recirculation line about 20 years ago, I ran recirculation line from master bath second floor to water heater in basement. I tied the recirculation line into water heater cold water input line, with pump and appropriate check valves. Worked fine for a number of years until pump quit.
    When pump quit I took out pump and reconnected the line. Fully intending to replace pump. During required period of procrastination of getting a new pump, I noticed that the system still worked. I had a gravity flow system.

    Everybody is happy for a number of years until wife kicked me out of the master bath and to the basement. Then after a few years she began complaining that if I showered in the basement while she was in the shower upstairs, she only got cold water. After waiting a few years to see if the complaining would stop, I decided that the check valve was faulty. She also recently began complaining that she got cold water if the guest bath was being used.

    A few weeks ago I replaced the check valve. Old valve was coated with mineral deposits. The new check stopped the "cold water" complaints. However, the circulation due to gravity flow had stopped. I pulled the new check valve and it was a little sticky on opening and the flow apparently wasn't enough to open it.

    Being cheap I didn't want to purchase a pump when I had had a gravity flow system that worked. Being lazy I didn't want to do the work repiping the recirculation line to the drain valve as a gravity system is supposed to be done.

    While I debated, I put on my plumbing ingenuity hat. I changed the check valve from horizontal to a 45 degree angle. That cause the swing valve to open slightly so that I get the gravity flow and the back pressure on the recirculation line when a faucet is opened is enough to causes it to close and prevent cold water from going up the recirculation line.

    Everybody is happy once again, for now.

    Replace that check valve.
    Harold,
    Thanks. My check valve is a swing valve, threaded on one side but welded on other. Can you open the big nut and clean the inside as an option? (We do have fairly dirty/corrosive water here.) Also, my check valve is in the line to the pump, not between the pump and water heater. A problem?

    At least my wife lets me use the inside bathroom, for now.
  • Apr 9, 2013, 11:50 AM
    Milo Dolezal
    There should be swing-type check valve + hose bib between pump and water heater. Hose bib is there to bleed the loop.

    Milo
  • Apr 9, 2013, 12:15 PM
    hkstroud
    The old check valve I removed had such a build up of mineral deposits I couldn't get it opened up, even when put in a vice. Probably have to cut the line, remove and replace.

    Milo,
    Why must the check valve be between the pump and the heater?
  • Apr 10, 2013, 09:07 AM
    bills1260
    Quote:
    Originally Posted by hkstroud View Post
    The old check valve I removed had such a build up of mineral deposits I couldn't get it opened up, even when put in a vice. Probably have to cut the line, remove and replace.

    Milo,
    Why must the check valve be between the pump and the heater?
    I would like to know the answer to that, too.
    Thanks. Bill
  • Apr 10, 2013, 09:42 AM
    Milo Dolezal
    Check valve will prohibit in-rushing cold water from the bottom of the hot water heater from flowing backwards through the loop when you open a hot water faucet somewhere within the system.

    In addition, since there is higher pressure inside the water heater than at the end of the return line, water will push against the rotor of the pump preventing it from starting up.

    Moreover, if you have timer on your pump, and pump goes ON and OFF several times during the day - check valve will help to maintain water inside the pipe ( keeping it primed ) allowing for easy start up when pump turns ON.

    Some later model pumps have check valve built in to the union, therefore are hidden. The only way to access them is by removing pump from the pipe.

    As far as I know, just about every pump manufacturer recommends installation of check valves.

    Hope that explains... Milo

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