Identify plastic tank type

Thanks, do you think there is a difference between the different polyethylenes? hard or soft?
I will order some welding sticks for polyethylene.

It's probably polyethylene. Here's a list of some manufacturers:

RONCO - one-piece linear polyethylene

TODD — one-piece polyethylene. Marine tanks.

TRIONIC — one-piece polyethylene.

ICON TECHNOLGIES (Camping World) — ABS plastic

Ameri-Kart — LDPE polyethylene and ABS.

D&M Plastics — polyethylene

INCA Plastics Molding — polymer resin

All-Rite — polyethylene. Makes custom tanks for out-of-business RV companys.

Dura-Cast - polyethylene, Linear Medium Density (LMDPE)

Freeman Engineering - polyethylene

Might be some info here or similar websites--just Google Rv tanks.

The potable water tanks were/are polystyrene (sp?)resin (white) that is quite flexible, while the older grey and black tanks were dark coloured ABS and much stiffer. It seems they now have a newer type grey and black tank from what these people say.

http://www.plastic-mart.com/category/33/rv-water-tanks

You can ask them your question about repairs or replacement I would think.

my new to me Lance camper had a leak in the drain nipple on the gray water tank. I bought a plastic welder from Harbor freight. I never did figure out what type of plastic it was, however if you look on line (you tube) you can easily find vids on plastic welding, and I used the "bridge" method with the plastic welder. It worked out pretty darn good, I backed that up with JB weld for wet. I have filled the tank and its been sitting wet for about a week now and no sign of any kind of moisture. My guess is time will tell if this was good long term fix or not.