When I asked Dessalator's USA rep Mark Fruehauf at Balcen (info@...) about how best to winterize our watermaker I got this reply:

"For winterizing I recommend doing a fresh water flush and then filling the High Pressure pump and membrane pressure vessels with non toxic water system antifreeze.  The easiest way to do this is to use a utility pump to pump the solution into the inlet of the high pressure pump.  It is also very important to make sure to blow out all fresh water from the product water lines and  flow meters"

I've done this for three years and so far it has worked well with no measurable degradation in either the quality or quantity of water being produced by the watermaker.  

--
Mark McGovern
SM #440 Cara
Deale, MD USA