My new sump pump is pre-plumbed with 1.5" PVC, but my existing discharge line is 2". Is there any problem with connecting the 1.5" pump outlet to the 2" discharge line using a flexible Fernco coupling on the vertical section of the line? The check valve will be below the Fernco connection point, right at the base of the pump.

Update: I installed the new sump pump with the flexible 1.5" to 2" fernco coupling, and it's working like a charm. Thanks for the answers.


Not a problem.

FWIW, I installed the check valve above the coupling so that it would prevent draining when I remove the pump for service. The valve I used is threaded, so I can still remove it if needed. No problems after many (20?) years of service.

Tip: Put the pump in place without the coupling and mark the PVC pipe to indicate where the coupling should be positioned to center it over the joint. That removes any worry when reassembling the plumbing.


That will work fine. What you want to avoid is reducing from say 2" to 1.5" as this can cause things to get stuck and block the flow.

But you should be good to go with a 1.5" opening up to a 2".

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.