I bought one about three weeks ago, what a nightmare. Three hours of sticking an 1800 psi hot water pressure washer in the top, the car park was covered, I was covered, infact just about everything was covered. In the end I gave up and decided to leave the rest in it. Filled it up with 400L of water and left it for two days and the TDS was the same as when I put it in there(001 tds). So if its semi-dry leave it in there
by the way mine had PVA glue in it and had stood for about 7 months