DIY Solar Water Heater. A Homemade "flat panel" COPPER COIL Solar Water Heater. Easy DIY. Full Instructions. super hot temps (sustained at 165F+). fast hot water. no electricity needed. easily hooks up to standard water tap/garden hose. reaches temps well over 150F (water pasteurization temp) so it works to clear/kill any pathogens (if a non-municipal source is used). it's super portable so it's good for camping/off-grid/emergency as well as everyday use. couple of notes: water flow rate verified with a measuring cup and a stopwatch. (roughly 1 oz. of hot water every 1 to 1.5 seconds and scaled up - one gallon every 2-3 minutes or 20-30 gallons per hour). about the copper tubing: a 50 foot roll of tubing is much cheaper than smaller rolls connected. *only $24.95 for 50 ft (but $17 for a 20 ft roll and $10 for a 10 ft roll). the glass is just standard window glass and the paint is flat black. it's thin flat design allows it to be easily stored in a closet, under the bed etc... *"seal it" according to your climate conditions and whether you plan to leave it outside.