the back side of my caravel is an open tapestry

[bobmstein]

Removed six feel of the underskin of my newly purchased 71 caravel in order to rid it of damage and neglect only to discover zero holding capacity. Found a twenty gallon plastic tank measuring 30 x 40 and has a 3 and 3/8ths to 5 inch taper; 5 inch being the limiting factor. My goal is to plum everything to the tank pat myself on the back and moving on to the next priority. Any pitfalls to my logic?

[Melody Ranch]

You do not want to plumb everything to one tank. Read the threads here on why not.

[idroba]

You are talking about gray water, right? No gray water tanks on those years. I have thought about doing the same thing on my '71 Caravel but I would use a larger and deeper tank with some more capacity. You can drop the belly pan a couple of inches in that area without harming the road clearance. My '74 20' Argosy has a dropped tank in the rear which was still covered with a belly pan which had also been dropped about 3 inches. I can't show any photos, as I am not at home, but someone with a dropped tank and belly pan on an Argosy might post a photo so you can see what they did at the factory on the 20's. I have towed mine maybe 40,000 miles and never had a problem with clearance.

[bobmstein]

Is it possible to install a black water tank and run a 11/2" pipe around the tank to a valve that would open and restrict the black water tank? Is their a valve that can open and close in two directions or would I have to install two seporate valves?