[Dave_E]

I would be very cautious about connecting pressurized water to a manual head.
Fresh water is definitely preferable to salt for rinsing a marine head, but the head must be set up for an inlet pressure of 30# or more, which I would doubt your $150.00 head is.

For sure! I had contimplated teeing off the supply line to the water pump (directly from the tank), but am not for reasons already discusssed.

 

[sailak]

The OPs problem could get worse. Our Groco was "returning" stool to the bowl during flushing….not good.

If we're going to be away from the boat for a few days we pump the bowl dry then refill with fresh water pumping a couple gallons through to "rinse" the system. We have no foul odor in the head.

 

[hellosailor]

Dave, have you looked inside a toilet tank in a home toilet? Are you familiar with the fill valve?

Forget the old ones with the big bulb on a stick, they're obsolete. The new ones use a circular float that comes up around the fill tube, and the whole assembly (tube & valve) is about five bucks. That's all you need for a proper and legal "sanitary break" on a fill.

If you look it over...it allows water to enter and fill, with or without a tank, and it is physically impossible for the water supply to be contaminated with "toilet water". Which, by the way, is also perfectly potable in a toilet TANK, as opposed to the bowl. So you've got a $5 part that has all the fancy engineering done. Just needs a hose and optional cut-off valve to supply it. And not just one, but TWO up-to-code sanitary breaks protecting your water supply.

If your holding tank is located above or equal to your fresh water tanks...that's a bigger threat than plumbing fresh water into your head.(G)