Do you service your customers systems spring & fall ? Do you also "blow" out the system in the spring start-up process ? If you dont..you should. This process can tell you alot of how your customers system is going to perform once you turn on the H2o supply. If you should encounter any system problems due to the system being off over the winter months, it is now easier to repair the system due to you have NO water in the pipes,valves etc. A simple process to do just as if you were shutting the system down. Connect the air supply then open each controller / zone using the system control panel ( manual on-off ) and check that each are working properly, including the backflow device ( repair if needed as necessary & re-test ). Ok,,,some will agree...some will disagree Better to "Air it out" than get wet and dig in the mud.