Originally Posted December 10, 2004

Cruising and living on the St. Johns river presents a problem many of us tend to ignore; the odor and look of river water in the bowel of the toilet.  Stephanie made the request a year ago that she wanted the ability to flush the toilets (heads) with both outside water (when cruising in blue water) and fresh water when on rivers.  This seemed like a fairly easy task to accomplish until I started the project.

Our Model 8 Skipper head from Wilcox-Crittenden could not handle any head pressure on the flush water inlet.  I learned that lesson the hard way when I first attached it to the 40psi fresh water line.  But even worse, when I did finally realize I needed to isolate the flushing water from the drinking water (in case of backflow) even the head pressure of the outlet form the fresh water tank being one foot higher than the input to the head would cause the bowel to overfill and flood the bathroom (OK – Head).  I tried putting an anti-siphon loop and valve on the input, only to realize to-late that the valve worked the wrong way (that is when you would attempt to pull water from the tank, it sucked air).

So – the solution that worked was replacing the anti-siphon fitting at the top of the loop with a manual valve.  The only draw back being that the user has to remember to open the valve prior to pressing the foot pedal to flush – and to remember to shut it off afterwards.  One might say – hey – that’s an accident waiting to happen (the flooding that is).  But fortunately the fresh water holding tank I installed is only six gallons.

The pictures below show the major components of the design.  The V-berth cabinetry under the bunks had ample room for a 6-gallon holding tank.  I built a shelf for the tank and equipped it with a 12VDC solenoid operated water valve.  The switch to the valve can be seen in the 2nd picture just to the right of the fold-down step.  At the top of the tank I mounted the Tank Watch system from SeaLand.  To fill the tank, one pulls the switch water flows into the tank from the main fresh water supply.  When the holding tank is near full the warning light on the Tank Watch illuminates and the switch can be pushed in (off).  There is no need to actually observe the tank during this filling operation.

Output form the tank goes to a selector valve below the floorboards as seen in the 3rd picture.  There one can select either fresh water from the holding tank or raw water from the seacock-fed strainer.  In the photo one can also see the forward deck wash-down pump.  Feed water to this pump is also derived from the manifold I designed so that you can have fresh water on the foredeck for showering or raw water for rinsing the anchor and rode.

Freshwater head

Freshwater holding tank

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