Water Leak at Toilet Flush Valve

[Lazlo]

I’m new to Airstream’s and in need of help. When I went to hook up water to my 1964 Airstream Safari, My wife notice water spraying from the base of the toilet. Upon further investigation and accessing from the back of the toilet I noted a strong stream of water coming from a brass threaded component on the flush valve. The stream of water coming from the brass part of the valve was hitting the floor and splashing into the camper.
What is the purpose of this brass valve. Should it have a cap on it?
The brass threaded part is behind a right
angled cover and points down at the floor. My thinking is that it is a drain of some sort for draining water for winter storage. It is a small diameter, less that 1/8 Npt. I’m really not even sure it’s a pipe thread.

[Lazlo]

Water is flowing out the bottom brass valve when I turn on the water supply. The brass valve has a stem with male threads. Not sure what it’s used for. Should it have a cap on it?

[Bill M.]

Do not know about that era trailers. One possibility, is it a fitting to connect a hand held spray line? Many Airstream toilets had a external, hand held sprayer for cleaning the bowl. That is about where the fitting is installed on my new toilet. Certainly you are going to have to cap it off or install the spray line to use the water system.

[Lazlo]

Would anyone know the male thread size on the brass fitting? It measures .290 on the thread od.