There are no special requirements for winterizing solar collectors in climates when the pool is shut down for the winter, as long as the collectors and piping have been installed to allow the system to completely drain each time the pump cycles off.
In order to protect the collectors – as well as appurtenant components such as end caps and pipe fittings – against unusual or severe freezing conditions, one of the following two procedures should be followed when freezing weather is imminent:
1. Turn circulating system off and allow solar collectors and piping to drain. Isolate collectors with gate or ball valve in collector feed line and a check valve in the collector return line. Switch the solar control to the bypass position. The pool filtering system may then be turned back on. When freezing conditions have passed, open isolation valves and switch the solar control to "AUTO."
2. Switch the solar control to the "COLL" position so that water circulates through the collector. When frees Installations where collectors are located below pool water level, where collectors lie flat on a roof or patio cover, or which have a piping configuration that does not allow for gravity drainage of water must be checked to ensure the collectors and piping are drained.
Operating Solar During Freezing Conditions
In some parts of the country, pool owners operate their pools throughout the winter even though light freezing conditions may occur. If your system is equipped with an isolation valve in the collector feed line and check valve in the collector return line:
1. Turn the circulating system off and allow at least 30 minutes for the solar collectors and piping to drain. If your installation does not allow for gravity drainage, the system must be manually drained.
2. Once drained, close the isolation valve in the collector feed line. If your system is automatically controlled, switch the control panel into the "pool" or "off" position. Turn the filtration system back on to protect it from freezing.
3. When freezing conditions have passed, open the isolation valve in the collector feed line, and if your system is automatically controlled return the switch in the control panel to the "auto" position.
If your system is not equipped with isolation valves, or cannot be drained manually, it is recommended to continuously circulate pool water through the solar heating system at any time the outside temperature is 42 degrees F or lower (this method is not recommended where temperature levels may drop severely).