I have an underground storm drainage pipe that is connected to both my downspout and sump pump drain. The underground drain pipe, the downspout and the sump pump pipe all tie together with a 3" tee.

Downspout Leak

The bottom of the tee is a male end to the female drain pipe that runs to the street, where the red arrow points. This isn't glued or sealed in any way, this is similar to how the rest of the outdoor plumbing is setup. I've adjusted the elbow at the very bottom to get everything as straight as I can but water continues to leak around this spot. I've tried caulking this in the past and it failed. I can't used a PVC solvent and glue as the pipe between the Tee and Elbow isn't PVC. I'm not sure how to stop it, any advice would be appreciated!

2 Answers 2


That piece of pipe that you say is leaking appears to be flex pipe and can be glued with PVC glue. If it absolutely doesn't glue up, replace it with a PVC piece.

  • I didn't know that Flex pipe and PVC could be joined. Is there any worry about the freeze/thaw cycle and glue that I should be aware of? Thanks for the tip!
    – Justin
    Commented Mar 4, 2023 at 21:14
  • Many flex pipes have a PVC inner and outer shell. The glue should bond well if applied properly. I'm in Fla. so we don't have freeze/ thaw issues. Since it's a downspout and shouldn't have water filling it my guess would be it will be ok. I also checked with the expert (my wife) and she said, that type of pipe (flex, funny and other names) is made to glue to PVC fittings in all climates. She had never heard of issues with using it in cold climates. ( they would ship product around the world. So I think she is correct)
    – RMDman
    Commented Mar 4, 2023 at 22:02
  • I was able to get the elbow out and prime/cement each end. Unfortunately it only had about a minute to cure before the sump had to cycle but it's holding and very little water is leaking! I'm leaving it open for another day to make sure it stays dry and the cement has more time to cure before piling more dirt on top and risk breaking the seal. Thanks for all of the input and knowledge!
    – Justin
    Commented Mar 6, 2023 at 12:49

I'd suggest checking for a clog in the pipe to the street, or upsize that pipe to 4", as it may simply be you're asking it to carry more water than fits into it, so it's backing up.

But it might well have a partial clog causing backup.

  • Thanks for the suggestion. Water flows through the underground pipe freely. Additionally, the inlet from the discharge pipe is sized down from 2'' to 3". I don't get any water spilling over the gutter either on this end of the house indicating water is backing up the downspout. Thanks again for the reply!
    – Justin
    Commented Mar 4, 2023 at 21:17

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