I have an electric sump pump which failed so my backup water-powered sump took over. The water-powered pump is relatively quiet but when the cycle is complete, it THUMPS HARD like pipes in an old house and is felt all over the place. Seems like an air lock to me, but having read a few posts, it resembles complaints about a noisy check valve.
How can I tell what is causing the thumping and if it is an air lock, is there a way to bleed the system?
(Of course I am replacing the regular pump as soon as possible.)