This is a great DIY Solar water heater project. Solar water heat may not be a sexy as solar electricity but it produces a lot more energy savings for the dollar and is something everyone can do.
1. The collector is easy to build using ordinary tools and skills -- its a fairly easy DIY project.
2. The collector is about 1/5 th the cost of commercial collectors ($140 vs $700 to $900 for a 4X8 collector)
3. Materials to build the collector are locally available -- the cost and hassle of shipping large assembled collectors is avoided. Shipping on a commercial collector is more than the total cost of materials for the PEX collector!