Tru Mark uses a Shurflo 3.3 GPM 12-Volt pump unit. The Shurflo technical services representative suggests using RV style antifreeze liquid. That is a propylene glycol liquid. Dow Chemical manufactures DOWFROST RVR that would be suitable.

Prior to this storage step we would also recommend running a "pump protector" or "pump saver" through the system. This should be done on a routine basis. You can find this in 32 oz. plastic bottles at a good paint store that sells commercial paint sprayers. I would add 1 to 2 oz. of the pump protector to a gallon of water and run it through the system for a couple minutes. This helps keep any remaining paint in suspension and flushed during the rinse process.  We suggest unhooking the hose connectors at the pump head to allow any excess water run out of the pump head. 

Another option is to remove the pump valve and diaphragm kits from the motor. Remove the 6 Phillips screws from around the edge of the pump head and the diaphragm kit with valve kit will slide off the motor shaft. In the spring when you put the kits back in all you need to do is spray some water into the pump head before you attach the hose connectors.