[Alyce Peters]

Is it OK to put a restricter on a new washer, because of old plumbing, and how do you do it?

[labman]

Is this the common problem of the newer washers having an excessive discharge rate and overflowing the stand pipe? If so, the easiest thing might be to add a smaller section of hose or replace part of the existing hose. The back pressure from a smaller hose goes up sharply for small decreases in diameter. You could even add a partly closed valve. Ball valves are becoming easier to find, and give better throttling than the common gate valves.

I have worked in the chemical industry, and it is quite common to specify a centrifugal pump that should be larger than you need, and then throttle it down with a valve. Should work for the one in your washer.