I am a first-time travel trailer owner, having recently purchased a several-owner used 1973 RV. I can only find one waste water dump valve, which is located on the larger waste pipe directly beneath the toilet. Another smaller diameter pipe is connected below that T-handle, so whenever I run the shower or the two sinks the water does not appear to go to a gray water holding tank, but discharges below the black water valve. Is it possible that there is a gray water holding tank with some other type of shutoff device?
Sam, (Wyoming, PA)
Wow, a ’73! The oldies but goodies are out there. So indicative of well preserved and cared for RVs! Indeed Sam, it’s likely your new acquisition only has that single, black water (toilet) holding tank. It was later in that decade when it became popular for RVs to have the luxury of a gray water waste tank as well. Years ago, it was common to allow gray water to simply drain onto the ground, but that is not permissible today in most locales.
The options are to hook up a portable holding container to capture the gray water, but this requires you to manually remove and dump it when full. In some cases, an addition of a small gray water holding tank is possible if you have the space to put one. I’m guessing this is probably not feasible on your trailer. The third option is to plumb one of the gray water fixtures directly into the top of the existing black water tank. But this too is dependent on your space limitations, plus it’s the least affirming option since it will require more-frequent evacuations of that holding tank. I’d probably opt for the external, portable waste tank. They are readily available at any RV accessory store.