Sustainable Energy Systems installs different types of Solar Water Heating systems depending on the buiding layout. Whenever possible, we offer 'Drainback' systems that achieve freeze protection by draining the water out of the collectors and into a reservoir when the pump is off. The controls will not allow the pump to be on when the collectors are colder than the tank (freezing outside). Drainback systems require the collector pipe loop to slope all the way to the tank to allow drainage. This is rarely a problem. When the building layout will not allow the pipes to drain to the tank, we use non-toxic antifreeze in the collector loop for freeze protection.