Swindon area?
Just nip in to Ionic's factory, I'm sure they'll be happy to help.
When I had my machine fitted there, they had several HUGE 4,000 litre tanks of pure water that they use for testing etc.
Also I'd be having serious words with whichever cowboy supplied your tank. I'd want a refund (or at least some money back) and I'd want it repairing, with any out-of-pocket expenses re-imbursed.