I have been planning a heat exchanger for my pool for quite some time. I'd like some reco's about pressures and pipe diameters. See attached diagram. The pool hose is 1 1/4" flexible PVC hose like this: [URL]http://www.poolsupplies.com/images/products/tn_105550.jpg[/URL] The pump is a standard Hayward 1/4 or 1/2 HP that generates somewhere around 20-40psi. It seems to me (and the pool expert who gave me the idea) that I should be able to use one of these saddle valves: [URL]http://img.diynetwork.com/DIY/2003/09/17/r107_1fb_lead.jpg[/URL] and some flexible aquarium or other rubber tubing. Some questions: Can I get a saddle valve for a 1 1/4" flexible PVC pipe? At 20-40 psi, will the saddle valve still be water-tight? What diameter tubing for the heat exchanger would be a good compromise between volume/throughput and surface area/heat exchange? 1/4"? 3/8"? What's good? I'll need a pressure differential to get the water flowing through the exchanger. Where? (see 1 and 2 in diagram) I'm sure 1 will work. Will 2 work? I mean, I'm adding water back into the input. Does that compromise total throughput? Do I have to worry about whether the exchanger tubing will burst?