I replaced my sump pump, including the check valve. With the new pump,
the system made a lot more noise, like water flushing. I checked and
discovered that the new check valve leaks - it lets the water go both
ways. I disconnected the output pipe a few feet above the valve, on
the output side. (Interestingly, the pipe was empty when I
disconnected it. I poured water in the output end of the pipe, and it
ran out of the input openings on the pump. I poured water into the
output side of the valve directly, and it ran out the other end
immediately. I was careful to be sure the valve wasn't backwards.
I checked the old valve, which is similar. It leaked, too. I checked a
third valve with a different design, and it didn't leak.
The new valve has the brand name Parts2O Sump Pump Check Valve
FP0026-6D. It's black plastic, about five inches long. It looks like
some kind of adapter, with one end threaded and the other unthreaded.
Each end fits two or more different diameters. In my case, it screws
directly into the sump pump. It has a rubber flapper inside, which is
open a little even with no pressure.
Is a leak like this OK? I can see how the valve might close if there
was more pressure behind it.