Over the weekend, a neighbor tried to remove a water softener installed outside their house, and broke the lines. I helped them fix it, but one of the solvent welded joints I made failed. The main water line is PVC and the piping in the house is CPVC. We used a slip transition coupler to go from PVC to CPVC. We used Purple Primer and All Purpose Cement, both labeled for use with PVC and CPVC.

I normally wait 30 minutes after cementing these types of joints before applying water pressure, but the water was turned on only a few minutes later. The joint between the coupler and the CPVC separated.

I primed and cemented both surfaces again, and reassembled the joint. 45 minutes later, I turned on the water and the joint failed again.

My neighbor was able to locate a sharkbite transition adapter at a hardware store 30 minutes away, so we ended up fixing it with that.

So my questions are:

  1. Why did the coupler and CPVC pipe separate the first time? I thought that this type of cement sets within minutes.
  2. Why did the joint fail a second time?
  • Did you hold the two ends of the pipe together (e.g a clamping action) for any length of time? Also, most pipe glues I have seen should set within 15 minutes but take a few hours to fully cure.
    – TylerH
    Commented Apr 5, 2021 at 15:59
  • 2
    For the second time, was joint cleaned back to virgin plastic? Quite a few glues will not bond well to themselves.
    – crip659
    Commented Apr 5, 2021 at 16:05
  • 1
    Yes, something was very wrong if the joint actually came apart. PVC cement welds the parts almost instantly. There's no going back after 30 seconds.
    – isherwood
    Commented Apr 5, 2021 at 16:10
  • 1
    What did the instructions say and what was the temperature? When the temps are low solvent welding agents do not cure as quickly. I will pressurize fairly quickly in the summer but winter give plenty of time, also larger pipes take longer.
    – Ed Beal
    Commented Apr 5, 2021 at 16:16
  • 1
    Please post a picture of the primer and cement which you used. I'm sure you used the right stuff but it never hurts to have a second set of eyes verify.
    – MonkeyZeus
    Commented Apr 5, 2021 at 17:21


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