New Fresh Water Head Flush Installation


Sustaining Member
It seems to be common knowledge that using fresh water for flushing the head is the best protection against foul odors leaching through plumbing hoses. A few different arrangements have been used for accomplishing that in boats like ours, including:
1.) Replace the traditional head with one designed for using pressurized fresh water
2.) Installing valve(s) in basin drain and flush-water lines so basin water can be used for flushing
3.) Using combination basin faucet/shower head for directly irrigating the bowl with fresh water

Each of these have their trade-offs of economy, convenience, elegance, and simplicity.

Fresh water flushing is provided by the yellow valve handle at upper right in the image, just below the cabinetry. The fresh water is delivered to the bowl through a tee into the sea water flush hose at the rear of the head.

The installation includes a quarter-turn ball valve (the yellow handle), which passes pressurized fresh water through a specialized anti-backflow valve for flushing. The special valve includes double check valves, separated by an air gap, specifically, Watts 9D-M3.

Operation is very simple. The sea water sea cock may remain open, whether sea water or fresh water is to be used for flushing. If sea water is to be used, then the usual procedure of opening the "wet flush" valve on the hand pump applies. Otherwise, if fresh water is to be used, open the fresh water valve for a short period to introduce fresh water into the bowl, through the rim, and then hand pump the bowl to empty. Guests need never know about the "wet flush" valve on the hand pump, so less user instruction is needed.

In my installation, I used 3/8" white PEX tubing with SharkBite Push-to-Connect fittings to tap into to the pressure fresh water system enclosed within the vanity. After the Watts double check valve, I used 1/2" white PEX with SharkBite copper ring crimp fittings for a clean aesthetic.


36 RH #1 Rooster
Perfect timing finding this. I am headed down to tackle more of my nasty head issues. I particulary like your double check valve as this provides the required barrier between potable water system and flushing fw system. The valve before allows isolation too. I even like your access port for something to consider for burying stuff. My head deck has about 15 holes in it from different head configurations. The one I removed was mostly held down by calcified sewage hose but also 3/8 galvanized lag bolts threaded into the shower pan/head fiberglass shell. As I said, perfect timing, you inspired me.

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
It seems to be common knowledge that using fresh water for flushing the head is the best protection against foul odors leaching through plumbing hoses
I used to believe this too, and it is partly kinda sorta accurate. That said, many many boat owners do nor recognize that head hoses (and all other layered hoses for all other liquids, like diesel) have a finite life span.
After about 20 years, in round numbers, they can start to permeate. Changing out the hoses will eliminate odors from waste and also fuel systems when done regularly. When you acquire a vessel built in the 80's, unless it comes with a record of recent hose replacement, confirmed by a total lack of unpleasant odors, best to assume it's way overdue for replacement of them. While the cost per foot will cause grumbling (me included), given the long time frames for this sort of maintenance I believe that it amortizes out very well.
From past experiences shared here, also look closely at the factory OEM hand pump in the head compartment. That bellows can emit a potent odor when it's old and nearing end-of-life.


Sustaining Member
I even like your access port for something to consider for burying stuff.
Actually, that access port is from the factory, for access to a chainplate, or shroud anchor. Nevertheless, the cavity within is big enough for storing/hiding something.

I'm glad you have found the post helpful. I considered all other arrangements that I am aware of, and this, to me is the most "elegant" as to effectiveness and simplicity. Cabinetry is already crowded with hoses, so adding more can be a major challenge in avoiding problems. Plus, my arrangement does not add any extra steps to the traditional flushing operation: instead of turning the pump valve for wet flush, you turn a different valve for the same effect. And salt water can be used at any time, simply by using the pump valve instead of the pressure water valve.

Last year, I had replaced all of the hoses in the head, and I removed and cleaned the holding tank. I also replaced the head pump with new. But I was disappointed to find that there were still some head odors. Since installing and using the fresh water flush, those odors are for the most part entirely eliminated.
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Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
My freshwater head system has zero smell. With seawater, it stank and grew organisms in the bowl.

The grand proof of saltwater ick is my saltwater foot pump. Seawater sits in it all the time, and boy does it stink when pumped (every time I come aboard). Rotten eggs. Last year I installed new foot pumps, and in a week the smell of the saltwater pump (not the freshwater foot pump) was rotten eggs again.

I have compulsively thought-projected a solution. Currently I plan to inject bleach into the outlet with a syringe, to try to sterilize the diaphragm pump. Or destroy the diaphragm. The stink those first few pumps is baaaad.


Junior Member
The E 32-3 has 3 fresh water tanks and the way we sail; overnights, weekends, and annual 10 day or so coastal cruising we really do not need that much tankage. We do not use the built n tanks for drinking as even after removing and cleaning the tanks, the hoses hold unknown nasties and we take a new 5 gallon tank aboard for potable water. So, I use solution number 4: re-route bow tank to feed the head. Very simple and plenty of H2O for our use. No smell and joker valve is gonna last a lot longer without the salt buildup.

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
I am one (the one?) who doesn't understand not using sailboat water tanks. Clean them as necessary, replace hoses maybe, put in some Clorox if you like. Water is designed into cruising boats, pressurized to sink and vanity, and contained in hidden tankage. To carry all that stuff around and not use it seems to miss something.

If concerned with unknown poisons, consider that the drinking water in most cities travels through 100-year-old pipes and nobody thinks twice.