I second the motion on plastic-mart.com tanks. My 50-gal gray water tank came loose (it's embarrassing) and got dragged under the stepvan, pushed along by the rear wheels, for at least a few hundred yards while I was thinking "what is that peculiar noise". It did tear up the threaded fitting where the drain is, and there are some hairy looking gouges, but I re-mounted it (with angle iron and threaded rods this time) and it doesn't leak.
Polyethylene is extremely hard to fracture, a rock will not hurt it and will probably not even leave a mark.
[Edit: yeah, according to the respective sites the PPL Motorhomes tanks are 1/8" HDPE while the Plastic Mart ones are 1/4" to 3/8". --KH]
post edited by TamaleTrolley - 2012/11/22 01:17:37