How to connect heads to freshwater tanks?

[Superg]

My 1985 3207 draws raw water into the toilet bowls. I meanwhile have two giant freshwater tanks that rarely get used, and nasty harbor water filling my toilet with e coli and everything else that gets washed into our waters these days. Makes sense to use the nice clean freshwater from my holding tanks to flush the bowls.

My toilets appear to be Raritan PH PowerFlush or 1980s equivalent.

I understand the following:
1. There needs to be an "air gap" between the fresh water system and the toilet in order to prevent bacteria from migrating into the fresh water system unless you have a special, commercial product

2. There is a Raritan system for about $220 called "Fresh Head Conversion Kit". NO info on the Raritan site, but it appears to still be a viable product.

Does anyone have experience with the Raritan kit or other home-built solution that fits the requirements of #1?

Thanks, John

[Superg]

After some thinking, I've figured this out. The Raritan kit isn't very elegant. The Jabsco overpriced. I'm going to install a stainless steel 1/2" normally closed solenoid valve followed by a good quality brass vacuum breaker with check valve. leave the toilet on flush only, and install a nice button to turn on the solenoid and put water in the bowl. Less than 100 bucks for better quality parts than in either of those kits. When completed I will post.

[tomschauer]

You also want to remove the raw water impeller and bypass that housing with the fresh water. Also, if you plan to tap into the 50amp feed to the toilet I would add a 10amp fuse to the solenoid.

[Dad Joke]

This is what I did on my previous boat:

I installed a 3-way valve on the sink drain (it can be drained overboard -or- it can be drained to the head intake) and another 3-way valve on the head intake (it can take in water from the sink drain -or- raw water from outside).
To flush the head with fresh water I fill the sink with water, turn the valve at the sink drain toward the head intake, turn the valve at the head intake to take in water from the sink drain, then pull the sink drain plug and flush the head.

This configuration addresses the air gap requirement and gives me the option to use raw water for the head during a long cruise and then do the final flush using fresh water. This is also an easy way to add treatment chemicals to the head and holding tank and to winterize the head after winterizing the fresh water system.

[Superg]

Dear Dad joke, Love that solution. Very clever!!

Well, I decided to go all-in. I finished converting one of the heads using the solenoid/anti-siphon vacuum-breaker method. Putting together some slides with a voiceover which I will post soon. Turned out great and can't wait to convert the aft head next week.