Another Water Leak

[Montana_5964]

Have a water leak and can not find where it is coming from. Help! The carpet on the floor on the right hand side by the wooden grill to the first step up to bedroom. At first my husband thought if was leaking from the Shower when he was hunting last weekend. He removed the wooden grill and all is dry behind there and the basement is dry. All water lines that he could reach were dry. Again, The water seems to be coming in under the right hand corner under the carpet before the first step up in to the bedroom. Last weekend when he got back home the carpet was dry. He flushed out the tanks and plugged into the water source so I could start cleaning the next day. Before I even started cleaning an turning water on inside I found that the carpet was wet again. Don't know if the water is now coming from the main water line or shower. We are taking the trailer out again to Nascar races in one week. We don't want to have to unload the frig and make a special trip to the Dealer so I'm thinking of scheduling an appointment first thing in the morning the same day we go out to the track. But my husband says it will probably take them all day to find the leak. Any recommendations on where to look for the leak? Again basement is dry everything behind the wooden grill is dry. However, there is water stains on the inside of the wooden grill.