Need advice on adding a gray tank.

[WILDRTEXAS]

Its a lock. I am going to install a gray tank...I have surfed, read and researched until my eyes are bloodshot and my fingers are tired.
I would like to add a gray tank to my 1970 27' rear bath International. What is the largest size I can install? Girls like lots of water ... It says in my manual that I have a 50 gallon fresh water tank and shouldnt my gray tank be able to take that volume of water?
Should I install right before the black tank or should I install it up closer to the axles for weight distribution?? I havent opened the floor anywhere except in the rear so Im not sure what type room I have.
Also, Is it possible to flush the gray water thru the black tank? I realize that I may need to get a new black tank because if I cut a hole in the existing black tank to attach the gray I have an area for a potential leak.
Thanks to all for your information Cynthia

[barts]

Well, we've got a (stock) 25' 1971 Tradewind; I don't know how similar they are but some thoughts (which have prob. occurred to you already) are:

1) The gray water tank can be smaller than the fresh water tank by a bit; presumably you'll drink some, and use some to flush the toilet.
At a rough guess, you can prob. reduce the gray water tankage by the size of the black water tank...

2) 50 gallons of water weighs about 400 lbs... that's enough weight at the rear to significantly reduce tongue weight and also places a substantial load on the trailer frame & body, particularly on rough roads. Keeping the weight more centered would seem to be a good thing. Water weighs about 62 lbs/ cubic foot, so you're looking at 6.6 cubic feet of space - not tiny, but prob. doable somewhere. You can
also fit two smaller tanks if need be....

3) Unless you use a pump, flushing the gray water tank through the black water tank will require the gray water tank to be above the black... on our trailer, the raised toilet sits directly on top of the black water tank so this would not be practical.

4) It would be simpler to just empty the gray water tank via the same route the gray water takes now; this would not require cutting a hole in the tank. Perhaps there's a vent line on the black water tank you could use to flush it?

- Bart

[WILDRTEXAS]

what size gray tank sould I install? I have a 50 gallon fresh water tank. Also, I was thinking about installing the gray tank between the axels. Any problems with that location?