Roy, if your coach is similar to mine and you have the "hand tightening" fitting (see the white hose with the black plastic fitting) coming off the Redhat valve going to your water tank, you can just remove that hose and then see if water is coming out of the hose coming from the Redhat - when the Redhat is closed and the water pump is running. If no water comes out of the hose then the Redhat is not leaking.
Note that if the water fill hose goes into the bottom of the tank, you may need to drain the water tank first (but it may not be necessary as the diagram shows a one-way check valve at the bottom of the water tank - at least on my '05) before disconnecting the hose as described above, or be prepared to plug the hose. That sounds like a lot of effort but may be worth it to you over spending the money for a new valve.