Ordered 37 gallon fresh water tank and 37 gallon gray water tank today from Trionic (rotomolded tanks). 63Lx16Wx9H and plan to stack them on the rear floor of the camper under the sink possibly with some support between.
Also ordered a Thetford C402C left hand model cassette toilet with built in water tank (just seemed easier than plumbing into our main water system and worrying about pressures and such). Also, one tank of flush water = one full black water cassette, so easy enough to refill the flush water when you empty the cassette.
The Thetford will take about 4 weeks to ship from Europe since it is coming with other orders so we don't have to pay freight.
Going to get some more metal today...making good use of the flatbed already since I buy 20 foot sections! :-)
