Fresh-water flush

Rick over at s/v Cay of Sea addresses a problem all of us with our boats on salt water face: scale buildup in the head lines. It's an interesting solution...

I rebuilt our sanitation system in September 2011 after a disastrous week-long trip got transmogrified into an overnighter – the toilet stopped flushing and nothing I could do would make it work again.  So back at our home port, I took it all apart.  I forego the grisly details here, but the long and short of it was everything except the holding tank needed to be replaced.

It was a big job.  The white sanitation hose is very difficult to bend, and I strained my aging, arthritic hands far into the pain zone.  Same story with my back – all (I mean ALL) of this work is accomplished on your hands and knees.  After a week’s worth of intermittent work, it’s mostly put back together – I say mostly, because I still need to complete the overboard-off-shore pump-out circuit, which requires a rebuild kit for the second-hand pump I bought to power it.  However, the closed-circuit system with the holding tank and deck pump-out port are functional and work very well.

With this rebuild, I wanted to plumb the new toilet to flush with fresh water.  In one of Don Casey’s books or articles he suggests plumbing the head sink’s drain to the toilet flush-water intake.  The advantages are significant:  primarily, no more smell!  Seawater is what makes the head smell bad. There are microscopic creatures in seawater that alternately reproduce and die in the toilet bowl, especially if it’s unattended for a while.  Additionally, seawater reacts with human waste and leaves deposits of calcium on the insides of the hoses.  Eventually the hose diameter become so small that it clogs – which is the trouble that truncated our cruise last fall.  This is the way I plumbed our toilet on Cay of Sea, and it was easy.

You simply insert a T connector into the sink drain hose, and connect one side to the toilet flush-water intake.  When the sink drain sea cock is closed, the sink drains to the toilet.  After washing hands, there is usually sufficient water to complete the flushing.  If not, a few more pumps into the sink will provide what’s lacking.  I plumbed another T into the line to in order to retained the ability to flush with seawater.  You never know when that will come in handy.

T connector in sink drain.
The small-diameter white hose leads to the toilet intake.

The white hose leading into the bulk head is the seawater
source. The sink drain sea cock has to be closed and the
sink plugged with its stopper in order to get seawater to
the toilet intake.

The result?  Our head does not smell.  We can leave the boat closed up for weeks and it doesn’t smell. This is a huge quality of life improvement for any boat.