70 Commander - Upgrading Holding Tanks

[Acuda4me]

It looks like my 70 Commander I just acquired needs holding tank work. The black water tank is open, it looks like it had a direct modern dump valve that had fallen off (I found it in a drawer in the coach) and it seems to have the worlds tiniest grey water tank on the opposite (passenger) side with it's own dump valve. Can I just put a new modern dump valve that combines Black and grey dumping on the driver's side  (like a modern RV) and plumb into the old tanks? What is the best glue for new pipes to old pipes/tank? Also, there is a large span of  pipe between the bathroom sink/shower drain back across the bottom of the coach that looks large enough for an additional grey water tank, but it's just above the drive shaft. It seems odd to me that this coach has a black water tank large enough to store a season's worth of, er uhm, stuff and what looks like a 5 gallon grey water tank. I'll post pictures when I can.

[Oz]

As long as you have the room and route, you can do anything you want to, including replacing a small tank with a large one, placing them on the same side, and connecting the dump system together.  It's a matter of thorough evaluation of the space under your coach and your chassis area.

Putting on a new dump valve is easy enough, you just have to measure the ID and OD of the pipes and valve to make sure you have the correct connection sizes.

I believe epoxy glue is still used for the connections but, there may be newer, different glues available.  If anyone knows of them, I'm sure they'll chime in.

[ClydesdaleKevin]

ABS tanks are readily available in all sizes, with glue in fittings you can put anywhere once you cut the holes out with a hole saw.  Just make sure you use ABS cement, the black kind, not the multipurpose cement. 

The advantages of ABS plastic tanks are their longevity, you can configure the tank any way you want, they come in almost every size imaginable, and if they ever do get a crack or a leak, repairs are super easy and permanent.

Kev