Thanks for the offer, I certainly would get great satisfaction from learning to make them, but I'm so busy doing essential fit out jobs which I can't buy off the shelf. Filled up the FW tanks yesterday and one had a split, so rearranging plumbing just now, it's one thing after another. The auto bilge pump works very powerfully! I still have about 250 l in the tanks anyway so no hurry to mend the split. The original tanks were copper, I could have soldered the split in under half an hour, now I've got to mess about researching plastic glue etc.
The FW tanks are the only important bits made of plastic, and the only thing that's broken..
the tanks will probably be HDPE (high density poly ethylene - food grade)
The easiest method is to 'weld' them using HDPE rods or thin slices cut off a chopping board (Pound shop = good for this), and a carefully applied hair dryer or heat gun. Tack weld first, then seam. HDPE welding is at 300C, and it's relatively easy with a bit of practice (i.e. if I can do it, then anyone can !)
Milk bottles are made of HDPE so there's a cheap source of material, too. Don't get the temp too high, as the material will harden and not stay flexible.
Hi Johna, thanks very much for the photos, but they appear to have the spindle running through the wood, rather than an internal metal frame, I don't think they're for me because I would just break them..many thanks anyway, Jerry.