Is it an electric solenoid operated valve? Mine and others I've seen are a manual plunger valve, but this one looks different. In any case, find out how to take it apart. Start by calling Steve McPhereson. The picture is fuzzy but it looks like it has screws or opening holes on the top? It probably has o-rings, not washers, which are easily replaced by taking the old ones to a good hardware store. Replace them and grease lightly with silicone grease.