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  • #16
    Re: Water pressure too high after using hot water

    This is an interesting one. Keep us updated if you figure it out locally.
    Buy cheap, buy twice.

    Comment


    • #17
      Re: Water pressure too high after using hot water

      My first guess at why its just now happening would be that either city pressure has increased recently or if it has stayed the same, the t&p could have been relieving the pressure and he never noticed it?? Now it is stuck shut and the pressure has to go somewhere.

      Regards,

      Comment


      • #18
        Re: Water pressure too high after using hot water

        Another question....
        For a tank water heater... lets say for argument sake the actual internal tank is 5 feet high. When the tank is filled with water, is it filled all the way to the top at 5 feet? Or is it filled only to say 4 feet, leaving a bit of space open that is meant to allow for expansion of the water from heating it?

        When the water is heating, should the cold inlet line get warm? If yes, how far up should it be warm? 6 inches, 12 inches, etc?

        Thanks!

        Comment


        • #19
          Re: Water pressure too high after using hot water

          I just skimmed this thread.
          The inlet will get luke-warm as long as your not running hot water, running hot water will introduce cold water to the inlet and cool it.

          First I just want to restate how absolutely important it is that you get a working T&P valve on that heater...it is a MUST.
          I read through and from what it sounds like, the expansion tank is either water logged, or there isn't one.
          When a PRV is installed, you MUST install an expansion tank...you are seeing the result of not having one, or a defective one.
          A PRV is a one way valve, pressure from thermal expansion can't escape to the street main.
          In reading your pressure starts at 45 after using hot, then jumps to 160 it's almost a guarantee it's from thermal expansion as the water heater reheats after use in that 10 minute period after use...doesn't sound like a bad PRV...so far, though I might be wrong.
          I'd focus on the expansion tank and ABSOLUTELY get a new T&P on that heater.

          Comment


          • #20
            Re: Water pressure too high after using hot water

            Is it also possible that the thermostat on the heater is malfunctioning to a certain point causing the water to get hotter than normal, and thus causing more thermal expansion?

            Comment


            • #21
              Re: Water pressure too high after using hot water

              If you are still reading this thread wondering what to do, at least tell us where you live so we know which paper to watch for the water heater explosion / house destroyed news story...

              1 - You have to get the T&P relief valve replaced - it is an easy job but VITAL....
              2 - You have to get an expansion tank on the heater system...

              It would be neat to find out why this started but worry about that later...
              Fix this stuff NOW...

              Comment


              • #22
                Re: Water pressure too high after using hot water

                Originally posted by Ruudacguy View Post
                Is it also possible that the thermostat on the heater is malfunctioning to a certain point causing the water to get hotter than normal, and thus causing more thermal expansion?
                This is a good point(FROM AN HVAC GUY). What's the water temp?
                Buy cheap, buy twice.

                Comment


                • #23
                  Re: Water pressure too high after using hot water

                  Think I could add an Expansion Tank and replace the Pressure relief valve myself?
                  I done some plumbing. I added a new spigot and replaced an old one. So I have a torch and solder and such.

                  Thanks for all your help!

                  Comment


                  • #24
                    Re: Water pressure too high after using hot water

                    The biggest thing with the PRV is to use the exact same as the original. Let us know if you need some help. Our HD has a great set up of what an expansion tank setup looks like, maybe yours has the same.
                    Buy cheap, buy twice.

                    Comment


                    • #25
                      Re: Water pressure too high after using hot water

                      I just check the water temp. It is just about 120F, which is what I set it to 4-1/2 years ago when my first child was born.

                      Comment


                      • #26
                        Re: Water pressure too high after using hot water

                        How did you check, look at the temp setting or actually measure the water temp?
                        Buy cheap, buy twice.

                        Comment


                        • #27
                          Re: Water pressure too high after using hot water

                          Originally posted by gear junkie View Post
                          How did you check, look at the temp setting or actually measure the water temp?
                          I knew I should have specified.
                          I took a 2-cup pyrex measuring cup, stuck a meat thermometer in it, ran hot water into it so it overflowed for about 3 minutes. Max temp: 120.

                          Comment


                          • #28
                            Re: Water pressure too high after using hot water

                            Oh, if it helps any... I checked the pressure at my neighbors house tonight. His pressure is at 60. We ran the hot water for 5 minutes and checked again, The highest it got was 78. Now, he does have a water heater that is only about 1 year old and a Pressure Regulator that is only about 2 years old.

                            So, could a water heater that is "going bad" cause this sudden increase in pressure?

                            Comment


                            • #29
                              Re: Water pressure too high after using hot water

                              Sounds like you checked the temp right. Does your neighbor have an expansion tank?
                              Buy cheap, buy twice.

                              Comment


                              • #30
                                Re: Water pressure too high after using hot water

                                Originally posted by adamw View Post
                                So, could a water heater that is "going bad" cause this sudden increase in pressure?
                                One more time...
                                Originally posted by DuckButter View Post
                                First I just want to restate how absolutely important it is that you get a working T&P valve on that heater...it is a MUST.
                                I read through and from what it sounds like, the expansion tank is either water logged, or there isn't one.
                                When a PRV is installed, you MUST install an expansion tank...you are seeing the result of not having one, or a defective one.
                                A PRV is a one way valve, pressure from thermal expansion can't escape to the street main.
                                In reading your pressure starts at 45 after using hot, then jumps to 160 it's almost a guarantee it's from thermal expansion as the water heater reheats after use in that 10 minute period after use...doesn't sound like a bad PRV...so far, though I might be wrong.
                                I'd focus on the expansion tank and ABSOLUTELY get a new T&P on that heater.
                                Last edited by DuckButter; 01-04-2008, 11:29 PM.

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