Found the above switch on ebay, it simply fits inline, connects to my aquatec 8800 booster pump and when my tanks full, the float valve switches off the water and as soon as the back pressure gets to 40psi it shuts off the booster pump, BRILLIANT, just what I've been looking for. There's loads for sale from loads of companies BUT, they're all American and the postage is stupid, I've trawled the net and can't find them anywhere in the UK. Surely one of you knowledgeable types know where I can get one? I've chickened out of your idea Spruce, too electrical and complicated for me !!!!