Announcement Announcement Module
Collapse
No announcement yet.
water pressure spikes overnight Page Title Module
Move Remove Collapse
X
Conversation Detail Module
Collapse
  • Filter
  • Time
  • Show
Clear All
new posts

  • water pressure spikes overnight

    I am installing a thermal expansion tank for my water heater. One of the steps is to set the pressure of the tank to the house pressure.

    To get the house pressure, I put a water pressure gauge on my hose bib and left it there overnight. The daytime pressure is between 55 - 60 psi, which is normal. But the second (red) needle on the gauge measures the max pressure reading, which hit 120 psi sometime overnight. So I reset the gauge and left it on a second night and the pressure peaked at 90 psi, while the daytime pressure still remains in the 55 - 60 range.

    The configuration of the water supply for my condo is that I have my own backflow valve on the street for the municipal hookup which makes my system closed and isolates it from other units in my condo complex. The supply comes to my unit where I have my own PRV valve, which was replaced a few years ago and seems to be working OK. (I am able to make adjustments in the pressure by turning the screw on the PRV.)

    So I am stumped about where this overnight high pressure is coming from. If my PRV is working correctly and this pressure is not coming from the municipal supply, then could the pressure be created within my own unit? Is this normal? Should I set the pressure on my expansion tank to 60?

  • #2
    Re: water pressure spikes overnight

    First, because you have a RPBD which makes (your) system closed, your water heater should have had an expansion tank installed already. Installing one is a very good idea. The cause of your water pressure spike may be due to a faulty pressure reducer. More likely it's cause is an increase in your closed system caused by expansion from your water heater built up while not in use during the night which can't be absorbed by the main due to the function of the RPBD.

    Comment


    • #3
      Re: water pressure spikes overnight

      Once you have figured out what is causing your over pressurization take the expansion tank off of the piping and then set your tank to match the pressure of the house.
      AllurePlumbing.com
      • leak detection
      • drain cleaning
      • utility locating
      • conductor fault locating
      • and other specialties.

      Greensboro NC, Winston-Salem NC, High Point NC, Thomasville NC, Kernersville NC

      Comment


      • #4
        Re: water pressure spikes overnight

        Originally posted by Plumbus View Post
        ... The cause of your water pressure spike may be due to a faulty pressure reducer. More likely it's cause is an increase in your closed system caused by expansion from your water heater built up while not in use during the night which can't be absorbed by the main due to the function of the RPBD.
        Thanks, good points. So the cause is either 1) the PRV is faulty and allowing pressure to creep up overnight, or 2) the water heater is building up pressure overnight while not in use. A test to determine which is the cause might be to turn off the water heater overnight and see if the max pressure spikes like before. If it does spike, it's probably the PRV. If it doesn't spike, then it was probably the water heater. I will proceed with this test unless anyone has a better idea.

        Also, I just noticed that the temp setting is 130 degrees, which might contribute to higher pressure. I will turn it down to 120 degrees.
        Last edited by AverageHomeowner; 05-29-2012, 06:38 PM.

        Comment


        • #5
          Re: water pressure spikes overnight

          Don't start changing more than one thing at a time. 10°F is not going to change that much anyhow. If the prv is not that old and is the cause, try taking it apart, clean it and reassemble.

          This hose bib, it is after the prv, right? Some plumbers put one on before the prv for homeowners so they can wash their cars or whatever. If this is the case heavy usage during the day may mean low pressure and spikes at night. There is a neighborhood around here that shoots up to 325 psi from 125 psi.
          AllurePlumbing.com
          • leak detection
          • drain cleaning
          • utility locating
          • conductor fault locating
          • and other specialties.

          Greensboro NC, Winston-Salem NC, High Point NC, Thomasville NC, Kernersville NC

          Comment


          • #6
            Re: water pressure spikes overnight

            Originally posted by Gettinit View Post
            Don't start changing more than one thing at a time. 10°F is not going to change that much anyhow. If the prv is not that old and is the cause, try taking it apart, clean it and reassemble.

            This hose bib, it is after the prv, right? Some plumbers put one on before the prv for homeowners so they can wash their cars or whatever. If this is the case heavy usage during the day may mean low pressure and spikes at night. There is a neighborhood around here that shoots up to 325 psi from 125 psi.
            Yes, the hose bib is after the PRV.

            I have the water pressure gauge on again tonight with the only change being the lowered temp on the water heater. As you said, 10 degrees may not make much difference, but will measure it to be sure and isolate each change I make. For the next test, I won't be able to turn off the water heater (or turn it all the way down to "vacation" mode at 60 degrees) until this weekend since I need instant hot water on weekday mornings.

            I have a 30 gal Rheem natural gas water heater installed in July 2004. I wonder how many pounds of thermal pressure can be expected to build up overnight on my closed system. If I am within that normal range, I should be OK.
            Last edited by AverageHomeowner; 05-29-2012, 11:49 PM.

            Comment


            • #7
              Re: water pressure spikes overnight

              Why don't you just shut off the valve on the water heater overnight? By removing the heater from your system you will see if it's the cause of the spike. If you leave the heat on, the T & P valve may release. Turning the heat off or at least down to vacation is probably a better (and safer idea) idea, because your 8 year old T & P may not be functioning, since you haven't mentioned it's releasing before and you know your temp got up over it's release point.

              Comment


              • #8
                Re: water pressure spikes overnight

                The pressure peaked at 95 psi last night, so turning down the water temp from 130 to 120 degrees did not make a difference. Daytime pressure remains in the 55 - 60 psi range.

                This weekend I will test overnight with the water heater in vacation mode (60 degrees).

                Comment


                • #9
                  Re: water pressure spikes overnight

                  If I were you I would take the tank off and set the charge, while empty, and set the air to daytime pressure. If the tank is bad or not charged correctly it will be like its not even there. Still more than likely the prv.
                  AllurePlumbing.com
                  • leak detection
                  • drain cleaning
                  • utility locating
                  • conductor fault locating
                  • and other specialties.

                  Greensboro NC, Winston-Salem NC, High Point NC, Thomasville NC, Kernersville NC

                  Comment


                  • #10
                    Re: water pressure spikes overnight

                    Originally posted by Gettinit View Post
                    If I were you I would take the tank off and set the charge, while empty, and set the air to daytime pressure. If the tank is bad or not charged correctly it will be like its not even there. Still more than likely the prv.
                    i agree completely... now just because when you have the guage on the hose bib and you make "changes" in pressure at the prv does not mean it is working 100%... do what was said and try disassembly and clean then reassemble, or order a repair kit or cange out then go from there. once done set tank, drink beer. but also if your that worried about it being the WH just switch over to a tankless unit... no tank to heat = no expansion in system,so no more spiking either

                    Comment


                    • #11
                      Re: water pressure spikes overnight

                      Originally posted by Gettinit View Post
                      If I were you I would take the tank off and set the charge, while empty, and set the air to daytime pressure. If the tank is bad or not charged correctly it will be like its not even there. Still more than likely the prv.
                      The expansion tank is not connected yet.

                      I'm not clear how much of a pressure problem I really have. If the water heater creates thermal expansion overnight, then some increase in measured pressure can be expected. If daytime pressure is 60, what is considered safe/normal for overnight pressure buildup?

                      Comment


                      • #12
                        Re: water pressure spikes overnight

                        hold off on putting it in then until you make sure it is not the prv. Once that thing expands too far, its done....more often times than not.
                        AllurePlumbing.com
                        • leak detection
                        • drain cleaning
                        • utility locating
                        • conductor fault locating
                        • and other specialties.

                        Greensboro NC, Winston-Salem NC, High Point NC, Thomasville NC, Kernersville NC

                        Comment


                        • #13
                          Re: water pressure spikes overnight

                          UPDATE: I had to wait for the weekend to conduct this test. I turned my water heater temp down to vacation mode yesterday and then attached the water pressure gauge to my hose bib overnight. The daytime pressure is 60, and last night it peaked at only 65. Previously, when the water heater temp was set to normal, the overnight peaks were 90 - 120 psi. So this test is a good confirmation that the overnight pressure spikes are a result of thermal expansion buildup from the water heater and not a faulty PRV.

                          Thanks for all the advice and guidance from this forum that led me to conduct this test so I understand what's going on. I understand the effects of thermal pressure expansion in a closed system, but I was really surprised that the pressure peaked so high.

                          My next step is to set my new expansion tank to 60 psi, and then hire a plumber to hook it up. I already have it mounted, but I need a pro to do the rest. This completes a partial-DIY project that has been going on a long time ...
                          Last edited by AverageHomeowner; 06-03-2012, 07:37 PM.

                          Comment


                          • #14
                            Re: water pressure spikes overnight

                            UPDATE: I hired a plumber to connect a new Thermal Expansion Tank (TET) to my gas water heater. The daytime house pressure is about 60 psi, and previously my overnight pressure was spiking beyond 90 psi.

                            Following installation of the TET, I placed a water pressure gauge on my hose bib overnight and my pressure is now maxing out just below 65 psi. This means the TET is absorbing the pressure increase which is exactly what I hoped for. Nice to know that my fixtures no longer bear this increased pressure which should help to extend their life.

                            I love it when a plan comes together! Thanks again to contributors on this forum for their guidance!

                            Comment


                            • #15
                              Re: water pressure spikes overnight

                              Originally posted by AverageHomeowner View Post
                              Thanks, good points. So the cause is either 1) the PRV is faulty and allowing pressure to creep up overnight, or 2) the water heater is building up pressure overnight while not in use. A test to determine which is the cause might be to turn off the water heater overnight and see if the max pressure spikes like before. If it does spike, it's probably the PRV. If it doesn't spike, then it was probably the water heater. I will proceed with this test unless anyone has a better idea.

                              Also, I just noticed that the temp setting is 130 degrees, which might contribute to higher pressure. I will turn it down to 120 degrees.
                              Definitely make sure you get that checked out because that pressure could cause you some grief.

                              Comment

                              Working...
                              X