We were pondering this subject last year.  In many RV Catalogues you can
buy tanks, may sizes, may configurations. Installing it would be pretty
easy. The only thing I can't figure out is how to keep the water from
setteling in the low point - that is from where you come off the gray water
tank, go lower  and travel across the van back up to the sink drain fitting
on the other side.  Water seeks its own level so you would always have
water in the line between the sink and the gray water tank-you wold also
need a "trap" of some sort ( with a clean-out)  or you would constantly
have that "grey water smell" inside you van.You can purchase a slide type
valve made by Valterra at any RV store (or through me) for opening and
closing the "emptying port" so that souldn't be a problem either.  This is
a challange to all you engineers out there......go to it!

Wendy & John
Cape Cod, MA

'85 Westy,   "S-CAPE"
'98 Passat

CAMPERS ON CAPE COD - SEPT 1999