I used Starbrite pink antifreeze the last two winters here in the Chesapeake and it has worked well. I used it for all systems including: air conditioning, heads, anchor wash, watermaker, freshwater system, engine and generator. All told it took ~16 gallons. It would be less if you have a second person who can tell you when the pink stuff start coming out of the system you are fillning with antifreeze. I also made sure to drain and bypass my hot water heater before doing the fresh water system. One of the winters we had a serious cold snap where the temperature did not go above freezing for close to 3 weeks. The antifreeze turned into a "slush" in the heads and I was concerned about the watermaker membrane. However, it appears to be no worse for wear as the output and quality in terms of TDS and EC readings are about the same as they were two years ago.
I would highly recommend that no matter how you winterize the watermaker that you drain the product water line/flowmeter. While you can do it at the back of the watermaker panel, I found that the easiest way is to undo one of the many connections in the product water line right where it exits the membranes. See the section circled in RED in the picture below:
Just loosen one of those connections and drop the tube low and a small amount of water will come out. It takes all of ~2 minutes and could save you a ton of hassle. I drained it the first year I winterized when I was being super careful and meticulous but I was in a rush last year and I forgot to drain it. Sure enough, the water froze and the glass tube of the flowmeter shattered:
I was quoted ~US$400 for a replacement flowmeter from the US distributor for Dessalator. Ouch. Figuring that this was an "off the shelf" part I got the manufacturer name and part number off the part and contacted them directly. CT Platon in France is the manufacturer and my flowmeter had "A10HS – CA251001" engraved on it. Thankfully, CT Platon is still in business and they still make the part. They quoted me ~132 Euros plus shipping for a replacement meter. When I send the Platon representative the pictures above to confirm that I was ordering the correct part number, he told me that the fittings looked fine and that they could just sell me a replacement glass tube and o-ring kit for ~77 Euros. So all in all, not nearly as costly a mistake as it could have been but one that I will NOT be making again. So learn from my mistake and drain the tube/flowmeter!
Below is some information for the flowmeter that is on my Amel SM Hull #440 with a Dessalator D160 watermaker:
Glass tube flowmeter type NG
Flow range : 10-100 L/min Air ( please advise if different)
Ref : GTF3AHS-E
100mm ceramic engraved scale
¼’’ BSPP brass rear connections
Brass fine control valve
Brass float / Viton O rings
I have also attached some of the documents that the very helpful and friendly rep from CT Platon sent me.
SM #440 Cara
Deale, MD USA