This is a coupling between the ABS pipe from a sump pump and a check valve so needs to be removable. Does one apply any sealant to make a leak-proof joint? I tried different tightness on the hose clamp, replacing the hose clamp altogether, and rotating the coupling, none of which is able to seal the joint completely. The leak seems to move a little when I rotate the coupling, but there is no visible cracks on it or the pipe.

Pipe coupling

  • Welcome here @P.B. You should probably provide some more details including taking a picture of the parts with the problematic joint disassembled.
    – Michael Karas
    Dec 26, 2020 at 1:27
  • Thanks for the suggestion. Since I now got it to a position that leaks the least, I'll take a picture when the pump no longer operates as frequently. The joint looks pretty unremarkable though. One end is an ABS pipe (from the check valve) and the other end almost identical to this.
    – P. B.
    Dec 26, 2020 at 1:48

2 Answers 2


Is your check valve upside down? or is your ceiling concrete and have a wet spot?

I typically use a 2" pvc union. Is that check valve spring operated or just a gravity flap? The union allows disconnect without being a clamp based fitting.

Don't put any kind of sealing compound on the furnco - rubber doesn't like chemicals.

  • The picture is looking down, with valve & pipe in horizontal position, and the valve label is facing up, so I believe the check valve must be spring operated (since there is no back flow). Is clamp fitting known to be this finicky? I was just reading up on connecting PVC fittings to ABS pipe, and it looks like it requires a rubber transition coupling with clamps..
    – P. B.
    Dec 26, 2020 at 14:13
  • You can use transition glue for abs to pvc. The furnco connectors are used all the time in commercial - they shouldn't leak. Possible that check valve has a weird size the furnco connectors are rated for specific pipe sizes. I'd check what it says on the furnco for size and measure the check valve size. Spring operated check valves aren't as good as the flap style. So the flow arrows are pointing away from your pump, correct? Dec 26, 2020 at 18:35

I repaired a friend's sump and discovered the value of the "check valve" because his system did not have one lol. If it's not sealing though you're sure you have more than tightened the clamp, then the size different between the hoses is too great. Might need a reducer/spacer to go between the backflow valve and the PVC pipe. BUT... it looks like you've actually already done that now that I look at the pic closer lol.

SO... at this point, if it were me... I'd go get some FLEXSEAL or silicone. Take the leaky joint apart, and apply some. re-attach. Wait for cure (24 hours) before testing for leak again. Be aware that FLEXSEAL will permanently bond with rubber (because it is liquid rubber), so be careful where you apply it.

  • I have the exact issue. Flex connector wouldn't seal against the very old concrete pipe. I went to Home Depot and they said I can't apply any of the proposed solution because my pipe is wet at the moment. Anything else that works in wet environments instead of Flex-Seal or Silicone?
    – Regmi
    May 10, 2022 at 17:16

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