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  • Repairing a one inch pvc pipe connection to a pump

    I am trying to repair a one inch PVC pipe connection going into the inlet (suction) side of a water pump. Due to improper mounting of the pump the vibration of the pump caused the cement joint of the pipe/fitting into the pump to fail. I cut the "old" fitting off and proceeded to "mock up" a new connection to the pump. The old pipe that I am trying to connect to is "thin wall" pipe commonly referred to as sprinkler pipe. I find it impossible to dry fit a one inch pvc "coupling" onto the old thin wall pipe to start a new connection to the pump. I have cut the old pipe back twice thinking that the pipe at the first cut was damaged or out of round to receive the new coupling.
    Is it possible that the old pipe went through several freeze/thaw cycles during the winter and caused the pipe to expand enough so that a new coupling fitting would not fit the OD of the thin wall pipe. This is the first time in many years of working with PVC pipe that I have had problems with fittings not fitting a pipe.
    Any suggestions would be welcomed and thanks for viewing my "problem".

  • #2
    Re: Repairing a one inch pvc pipe connection to a pump

    Something is amiss. Worked with many different types of 1" PVC including "sprinkler pipe" without a problem dry fitting a connection.

    Are you saying that the fitting will not go on at all? Like the edges match each other rather than the coupling matching the O.D. of the pipe?

    Are you sure you have the proper size pipe to fittings?


    J.C.

    Comment


    • #3
      Re: Repairing a one inch pvc pipe connection to a pump

      What probably happened was the pipe got so hot that it actually got bigger. It happens all the time when a pump loses it's prime. It will run not pumping water and the water in the pump will get close to boiling temps and soften the plastic. Once the pump turns off, the little bit of pressure in the system is enough to actually expand the pipe. When it cools, it's got a new diameter. I've seen one inch pvc swelled up to almost 4" and still holding pressure.

      By the way, suction lines on jet pumps is supposed to be 1-1/4"
      Frequently asked questions about pumps and tanks.

      Comment


      • #4
        Re: Repairing a one inch pvc pipe connection to a pump

        Thanks JCSPLUMBING and SPEEDBUMP for responding. The fittings I am trying to install will dry fit the new one inch pvc piping I am going to use for the new hookup. All the fittings that I sawed off the old installation are one inch Schedule 40 fittings. As indicated in one of your replies the "getting hot and causing the pipe to swell in diameter may be a possibility. Yet the cement joint that failed, which caused the problem, was a one inch Schedule 40 pipe going into a one inch x one and one forth inch threaded adapter screwed into the suction side of the pump. A one inch coupling will slip onto the schedule 40 pipe that was part of the failed cement joint. My second cut is about two and a half feet from the intake side of the pump. I know that my new fittings are the right size. The thin wall piping is the problem and at this time I cannot figure out the incompatibility between it and the new fittings unless the pipe has expanded and taken a "set". My back up solution is to use a flexible coupling. I would prefer to solve the problem with PVC fittings.
        Regarding the comment that an one and one quarter inch pipe should be running to the intake of the pump - this is an old installation and I have no idea as to why it was installed that way.
        Thanks again for both of your replies.

        Comment


        • #5
          Re: Repairing a one inch pvc pipe connection to a pump

          I don't think it has been heat swollen as I have not seen a jet pump generate that kind of heat or pressure. But I also haven't seen everything.

          Could it be that your at or near a bell end on the pipe?

          If you can put a pic on here and I'm sure some will be able to figure things out.

          J.C.

          Comment


          • #6
            Re: Repairing a one inch pvc pipe connection to a pump

            And example of the formed bell end on a piece of PVC.

            (Or it could be exactly as SpeedBump says and heat swollen. )




            J.C.
            Attached Files

            Comment


            • #7
              Re: Repairing a one inch pvc pipe connection to a pump

              It's not the bell end of the pipe and I don't think the pipe is heat swollen. The only other think I can think of is that maybe the pipe froze several times during the winter and increased in diameter enough to make it too large for a new fitting to slip over. This may be "far fetched" because pipe usually cracks or breaks when it freezes. The pipe is inside a concrete block pumphouse and is not insulated. Temperatures in this area of the Carolinas was as low as 20 degrees F.

              Comment


              • #8
                Re: Repairing a one inch pvc pipe connection to a pump

                See if you or someone you know can take a pic & put it here. Probably help alot if it's worth the trouble to you.

                I'll check back later as I'm sure others will also.


                J.C.

                Comment


                • #9
                  Re: Repairing a one inch pvc pipe connection to a pump

                  I have seen the heat swelling thing hundreds of times here in Florida. It happens a lot when homeowners or sprinkler guys put pressure switches on self priming centrifugals. Water level drops a couple feet and the pump can no longer make the max pressure needed to open the switch points and it nukes. In the meantime the pipe swells and the fittings actually shrink. You can twist the fittings that were put in with a pipe wrench with you bare hands after one of these events.

                  Remember; thin wall as we call it, or 160 as others call it is the same physical diameter outside as the SCH 40 and SCH 80. It's the inside that is different.

                  I'm not sure why your trying to dry fit the fittings though, just eyeball and cut. PVC is very forgiving.
                  Frequently asked questions about pumps and tanks.

                  Comment


                  • #10
                    Re: Repairing a one inch pvc pipe connection to a pump

                    I was dry fitting to make sure a new fitting would slip onto the original thin walled pipe. The thin walled pipe has either swollen due to heat expansion or is out of round enough that a new coupling fitting will not slip onto the old thin wall pipe. I guess I could put som pvc cement on the pipe and new fitting and try that. I have never seen a pipe fitting that would not slip partially onto a pipe unless the pipe had swollen to an increased diameter. Any other suggestions would be welcomed. Since I have cut the thin walled pipe back a least 3 feet I have a hard time believing that it is heat swollen from the pump overheating due to a loss in prime. Am I possibily wrong in that annalysis? Thanks for your assessment. Should I cut the pipe back further from the pump and hope that this cut would work with a new fitting?

                    Comment


                    • #11
                      Re: Repairing a one inch PVC pipe connection to a pump

                      take a caliper and measure the new pipe and then measure back further on the pipe and see if you can find the same diameter, then cut it there and re pipe, it,

                      I may be wrong but I would think the swelling would only be near the pump, (exactly what near is I do not know), I would think if you got 10 feet back you may be OK, away from the possible heat swell by the pump heat,

                      the only other thing I would think of if you can not cut back any further, is to use a heat gun and carefully heat the pipe up and slip in a correct dowel or tube for size, and used a gloved hand to reform it back down to the correct size,
                      insert the dowel into the pipe to keep it round and the correct size, as one works it back to the original size.
                      or enlarge it to work like a belled end on a pipe and slip the new pipe up into it and glue it ,

                      I have bent many a pipe using heat and have had them sag and deform, (electrical PVC)
                      I think if it would have got cold and froze it would have just broke the PVC split it. the stuff gets fairly brittle when cold,
                      Push sticks/blocks Save Fingers
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                      • #12
                        Re: Repairing a one inch pvc pipe connection to a pump

                        Speedbump is the Pump go to Guy, on wells and Pumps on Many forums! Now don't You chickens get Your Feathers ruffled !
                        I can build anything You want , if you draw a picture of it , on the back of a big enough check .

                        Comment


                        • #13
                          Re: Repairing a one inch pvc pipe connection to a pump

                          Speedbump nailed it!!! Seen that happen many times too. Only thing to do is cut back further (if you can) to get to unaffected pipe,

                          Comment


                          • #14
                            Re: Repairing a one inch pvc pipe connection to a pump

                            I sure appreciate everyone's feedback/replies. Thanks again for all your help.

                            Comment


                            • #15
                              Re: Repairing a one inch pvc pipe connection to a pump

                              Originally posted by engineer View Post
                              I am trying to repair a one inch PVC pipe connection going into the inlet (suction) side of a water pump. Due to improper mounting of the pump the vibration of the pump caused the cement joint of the pipe/fitting into the pump to fail. I cut the "old" fitting off and proceeded to "mock up" a new connection to the pump. The old pipe that I am trying to connect to is "thin wall" pipe commonly referred to as sprinkler pipe. I find it impossible to dry fit a one inch pvc "coupling" onto the old thin wall pipe to start a new connection to the pump. I have cut the old pipe back twice thinking that the pipe at the first cut was damaged or out of round to receive the new coupling.
                              Is it possible that the old pipe went through several freeze/thaw cycles during the winter and caused the pipe to expand enough so that a new coupling fitting would not fit the OD of the thin wall pipe. This is the first time in many years of working with PVC pipe that I have had problems with fittings not fitting a pipe.
                              Any suggestions would be welcomed and thanks for viewing my "problem".
                              May be a silly question, are You using primar,
                              and good practices ?
                              I can build anything You want , if you draw a picture of it , on the back of a big enough check .

                              Comment

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