Home made solar water heater 4 feet by 4 feet. Will work well for a small pool or hot tub. Will work even better if you have plastic sheet, plexiglass or glass to cover it. $250 obo. Will require a small submersible pump - on sale now for $63.99 at Cdn Tire: https://www.canadiantire.ca/en/pdp/mastercraft-1-5-hp-submersible-utility-pump-0624146p.html#plp There is a 4 by 4 glass window free here. I've been looking for a couple of weeks - pieces this larger are hard to find: https://www.usedvictoria.com/all/39649276#map