I've got a dry well in my house that floods, and I want to install a sump pump. The previous owner installed a 1.25 in pcv drain pipe through the wall and out into the back yard up near the rim joist. However every sump pump (that I've found) uses a 1.5in threaded outlet.

My plan was to use 1.5in pvc at the pump and bring it to the drain pipe, however I can't figure out to join the 1.5in pvc and the 1.25in pvc.

Nobody seems to sell reducers at these sizes and the only fittings I can find are threaded on both ends and I don't see how I could join that to a pipe. I'm obviously doing something non standard but I'd like to make use of the existing drain piping. What can I do?

2 Answers 2


Sump pump? 10 seconds of searching found a Fernco (rubber coupling, entirely suitable for sump pump use) that will do. More searching might find something else.

Fernco reducer

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For instance, a reducer bushing and a 1-1/2" coupling will get you there in PVC

Reducer Bushing

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  • 1
    The fernco literature says not to be used in any pressure applications so I looked on. Would an 8ft rise of the drain pipe be too much for the fernco that might be around 3.5psi for standing water? It says maximum pressure of 4.3 PSI.
    – reconbot
    Commented Dec 10, 2023 at 16:14
  • You're coming up 8 feet from the pump to the sill where the reducer will be, according to your question, so pressure will be trivial unless the pipe goes up another 8 feet from there, in which case 4.3>3.5 so still fine. Or buy a PVC reducer and straight coupling - probably that will cost less.
    – Ecnerwal
    Commented Dec 10, 2023 at 16:30
  • 2
    I've used Fernco connectors on my sump pumps for the last 30 years, as has my FIL. I've had pumps fail, but have never had leaks at the Ferncos.
    – FreeMan
    Commented Dec 10, 2023 at 18:05
  • Been searching for days for a pvc solution that wasn't suspect ftr - I'll probably give that fernco a try
    – reconbot
    Commented Dec 10, 2023 at 19:07
  • 1
    Reducer bushings are common enough. You could also put two threaded PVC parts together if threaded is all you can find for adapters.
    – Ecnerwal
    Commented Dec 10, 2023 at 19:17

I ended up using a threaded 1.50 to 1.25 reducer brushing and then a 1.25 threaded to slip coupling. It's what I could find at the big box store. Its not super pretty but it works!

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