This is a series of posts which details the work which was required to outfit our boat with a holding tank for toilet waste. The project grew over time to include a refit and reconfiguration of the entire bathroom space.

In the previous post, we cleared out the bathroom and stripped away the cabinetry and faucet. We prepared the surface and laminated a new partial bulkhead to the side of the hull. These steps meant we reached a point where the tank could be mounted.

I had designed the tank with two mounts on the left side, each protruding 10 cm from the tank wall. The intention of these protrusions was to place the tank some distance from the bulkhead on the left. This would provide access to the chainplates should they need to be inspected or replaced at some point in time.
On the right side of the tank, I had asked for three mounting brackets. These would provide a secure attachment to the additional bulkhead, which we had installed.

To mount the tank to the bulkheads, I had purchased a thick mahogany beam which I cut up into 15 cm segments, one for each mount. I drilled 8 mm holes through these pieces. The brackets of the tank would be mounted to these holes with M8 screws.
The tank was then manoeuvred in place, and I used wood screws, coming through the bulkheads to secure the mahogany pieces to the bulkheads themselves. This arrangement made sense as I could not have achieved the measurements accurate enough to make brackets which would attach directly to the bulkheads.

This probably does not make much sense in writing, so I’ll let a picture tell the tale.

Plumbing starts

The plumbing needed to be redone, not so much due to ageing of the hoses but rather that the tank drains and the waste selection valve required us to reorganise the whole area. The list below details the essential requirements for the new configuration:

  • One drain, from the tank straight to the deck fitting, for connection to a pump out facility
  • One drain from the tank, to the through-hull, making it possible to drain the entire tank while at sea
  • From the toilet, we should be able to select whether to pump straight overboard or to the tank
  • A vent line needed to be connected to prevent vacuum build-up when draining the tank and to allow expanding gases to vent from the tank
  • New seawater hoses for flushing the toilet

All in all, we’re talking about approximately 10 meters of hoses being run through the cabinet. We decided to remove all of the old sanitation hoses and completely replace them with new ones. The rebuild of the cabinetry would allow us to hide most of the hoses behind wooden panels, so the old ones would not have the correct lengths anyhow. This was the smelliest job as it required cutting open the old hoses.

With the tank, pretty much irreversibly mounted in place, we started to route the plumbing. The first hose to be run was the one for the deck fitting.

The location of the tank made it fairly simple to figure out where to drill the new hole in the deck for the waste water fitting. A 52mm hole was cut through the teak deck, top skin, core and bottom skin of the deck.

This opportunity to cut a new hole in the deck was a chance to also measure the thickness of the teak deck and thus judge the level of wear that has taken place since it was laid in 2004. We were glad to see that we had a thick and healthy teak plank left after the cutout.

To get a good seal between the deck and the new fitting we took the opportunity to sand the deck gently with the orbital sander so that the butyl tape, used as a sealant, formed a smooth bond with the deck surface. With a heat pistol, we heated the butyl tape so that it would set properly. It was still about minus five degrees celcius outside.

In the next post we’ll continue with the hoses and I’ll show you the spiffy new composite valves which we’ve decided to go with.