Part 2 of a 2 part series showing how to install a cheap cost effective solar hot water heater. Part 1 is available on youtube, this gets to the point. The tubing is safe in excess of 170F in terms of chemical leaching. Do not drink hot shower water;-) If you want a passive exchange system for areas that experience freeze overs, consider a 12v pump to a 30 watt solar panel with a copper loop that enters an insulated storage container. The roof tubing can then be filled with environmentally friendly anti-freeze as no roof/tube water is used in your house. This works great, the tubing is not intended for sun exposure BUT WE DID this video Uploaded time: Mar 31, 2008 11:27 AM almost 5 years ago and there is little breakdown of the material. Several freeze overs as this is a direct system but the plastic tubing expanded WITHOUT breaking. One time a connector popped loose but that was my fault (used an old hose clamp that was stripped verses a new one). I strongly recommend 1/2" 500 feet tubing as it is MUCH easier to work with. See Part 1
Also have a valve for direct systems so you can cut the roof out of the loop preventing ice cold water from entering during cloudy cold days. Additional glass covering will drastically increase efficiency. If you do "box it in" DO NOT line with foil or reflective material for the bounce effect. Go matt black as the heat transfer is much more efficient than flat reflection. Passive heat.