On SM243 the fill pumps for the heads draw water from separate thru-hulls in the “hallways” just inboard of the heads, near the center of the boat.  There are no vent loops for either head.

Kent & Iris

Kristy SM243

On Jun 26, 2019, at 4:22 PM, Mark McGovern <mfmcgovern@...> wrote:

Paul,

Not having an anti-siphon valve on the anchor wash pump shouldn't be an issue because the hose goes well above the water line so that even when heeled over saltwater should not be able to flow through the hose. And even if it did, it would just be pumped overboard out the front of the boat!

However, there definitely should be anti-siphon valves in each of the toilet water feed lines.  The Amel manual even states that they are there in the section on Toilets. My understanding is that this is because the hoses that run to the toilets are either right at or right below the waterline and they are certainly BELOW the waterline when you are on a starboard tack.  Given that, seawater from the intake could flow into the toilets if there is not at least a loop of line that goes ABOVE the waterline preventing water from flowing from the manifold into the toilet.  Amel uses a full anti-siphon valve and not just a high loop.  See this article for a primer on anti-siphon valves:  https://www.boatus.com/magazine/2018/april/anti-siphon-valves.asp

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