Deluxe DIY Solar Water Heater! Solar Thermal “Aluminum backed” COPPER COIL Water Heater! Easy DIY w/Full Instructions. Super Hot water, super fast. reached 125F in 5 minutes …and near 175F after about 15. no soldering required! uses just one coil of 3/8″ copper tubing (amazon $23) and push-to-fit connectors. only tools used were screwdriver, hammer, tin snips (or scissors), hack saw and a drill. great for use as a stand alone unit or can be hooked into home’s plumbing as supplemental heating for water heater. notes: using the aluminum backing adds roughly 10F to the water (but is optional). system is relatively lightweight and is easy to move and store *and the design allows for multiple units to be easy connected together (if a larger system is desired). details: outer board 1/2″ plywood 23.7″ x 23.7″ (sold that way – no cutting required). inner board 1/4″ plywood 19 3/4″ x 19 3/4″. glass 20″x20″ (or use Plexi-Glas).4 3/8″ Square wooden dowels. 2×2 lumber 2 pieces cut to 20 1/4″ and 2 pieces cut to 23 1/4″. Hardware: Four (#10) 2 1/2″ wood screws. Eight (#10) 1″ wood screws. Fourteen 3/8″ screws (to hold down the aluminum). 12 1.5″ (#16) wire nails. heavy duty heat resistant zip ties (or use wire). 5 3/4″ satin brass finish door pull (the handle).