Thermal Expansion

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  • This topic has 12 replies, 10 voices, and was last updated 21 years, 1 month ago by Avatar photoRobert Stephen Morton.
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    • #276437
      Avatar photofocusit

        Well, here a new one. We just recently serviced a home with a thermal expansion problem. Of course the T&P was opening from time to time. We found that the T&P valve would release when a cold water valve would open. Seems strange? I can understand a valve slaming shut and causing a problem, but open? Use on the hotwater side seemed to have no effect on the T&P valve. Closing valves on the hot water side had no effect. (example: lady would flush her toilet and the T&P would breifly open…mind you this was when the fill valve opened..not closed) We installed a potable expansion tank on the inlet of the water heater. This seemed to fix the problem but still don’t understand exactly why it was going off when cold water valves opened.
        All the basics were check. ie. electric elements, t-stats, water temp, check valves, etc. Note: she had a backflow at the curb and check valves on both the inlet and outlet of the water heater. Any input?

      • #294148
        Avatar photojomeister

          A third year apprentice should be able to answer this post.Lets see what tired plbg.has to say about it.Show us what you got tired.Should be know sweat for a person with 53 years experience.I will even give him time to check out the question.

        • #294149
          Avatar photorobertgf

            would a third year apprentice use the word know instead of no? just answer the friggin question

          • #294150
            Avatar photoSelgas

              I await the answer to this problimatical question with baited breath.

              Selgas Services Ltd
              Craftsman Gasfitters, Plumbers, Electrical Service Technicians

            • #294151
              Avatar photoRetired plbg1

                With the check valve on CW side the heater had no place to expand so it went out releif valve, boy am I good. How about you Jomeister do you ever answer anything , must be you dont know anything. OOOOOO. Come on show us your skill.

              • #294152
                Avatar photooscar

                  Tired plbg,you are about as good as a third year apprentice,not as good,but about as good.

                • #294153
                  Avatar photooscar

                    The problem occured when the cold side was opened tired plbg.The check valve has nothing to do with it.READ THE QUESTION YOU BIG NUMBSKULL.It didnt happen when the cold side was shut.Boy are you GOOFY,instead of “GOOD”

                  • #294154
                    Avatar photojomeister

                      You see what I have been talking about ,Oscar?Not only can tired plgb.not plumb,he cant read ,”are” is that the other way around?

                    • #294155
                      Avatar photobozo

                        Well tired plbg.Still trying to figure it out? Stop and think ,put some of that 53 years of experience to work LOL

                      • #294156
                        Avatar photoracefanone

                          CONDAR, did you check the incoming water pressure?I have run into a situation similiar to yours and the cause was the water pressure was to high.Just a thought.Hey Jomeister,Bozo and Oscar, cut the crap.Your comments are getting old.Get over it.

                        • #294157
                          Avatar photoCondar

                            Yes, we checked the pressure. Installed a guage before installation of the expansion tank. It runs around 50psig before thermal expansion and then around 70psig after. Of couse, stabling again at 50 after a valve has been open. Looks ok.

                            I was told by a local supplier that it could have something to do with the volume of water supplied. It’s piped with 3/4″ from the curb stop to the water heater. Another interesting note: the water heater is the last thing in line on the cold water side. He felt that a more than normal volume was rushing past the open line valve causing a “cold water hammer” on the water heater. I don’t believe it has/had anything to do with “normal” thermal expansion. ie. check valve blocking water from expanding thus using T&P.

                            The more you complain, the slower I work.

                          • #294158
                            Avatar photoracefanone

                              Condar,makes sense to me. Have a good one.

                            • #294159
                              Avatar photoRobert Stephen Morton

                                Condar. if that is the problem why dont you install a pressure limiting valve to that unit, you could check by installing a pressure guage at the hws & see what happens when the cold water taps are used.

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