Shower hookup to grey tank

[trout-fly]

I have a 1965 caravel,,,i`m putting in the original bathroom unit ,,,i`ve picked up a grey tank that fits between the back cross rails and it hold 14 gallon,,,,i`m putting in an inlet on the side to take in the 2 sinks,,, and have a vent on the top corner ,,,and to drain the tank is quite easy,,,but i`m not sure about the shower drain,,,,since the tank is up against the plywood {5/8 in.} and the shower outlet is on the top side of the plywood,,,how do i make the hook-up and whats to stop the water from slopping back up thru the shower drain,,i`m told i can have a threaded or a smooth flange installed for the shower,,,i hope somebody can help,,,,,,,thanks keith

[markdoane]

If you don't do something you will get water sloshing back into the shower pan every time you accelerate of turn a corner.

Your options as I see it are to put in a gate valve between the shower and the gray tank, or a check valve.

A gate valve is something you would need to open and close whenever you used the shower.

I would put in a check valve. Use the plastic ones made for sump pumps, they come in various sizes with hose clamp ends. Buy them at your HD or Lowes for about $10.

I also put a stopper in the shower pan when hitting the road.

Here is a picture of how I did mine. The check valve is the blue & red item in the lower center.