Plumbing changes facilitate offshore discharge

It almost goes without saying that the head is one of the most important devices to voyagers. It has to serve offshore as well as in restricted waters. More and more harbors are becoming designated no-discharge zones. As we have been trying to live within the various laws without spending an inordinate amount of money on energy-intensive Type I or Type II marine sanitation devices, which have yet to be approved for use in no-discharge zones, we have installed a system with multiple discharge options.

Because pump-outs are still few and far between, the scheme we are using is different than those shown in various catalogs and reference books. The accompanying sketch shows the various components. We use a standard manual head on our boat, but the significant difference is that we use a diverter valve at the output of the head to select overboard discharge or the 20-gallon holding tank. One leg of the diverter valve goes overboard, the other to the holding tank. I can’t see the environmental or legal difference between routing sewage to the holding tank before sending it overboard through a diverted valve or going overboard directly using a diverter valve. If necessary, we can “lock” the diverter valve to the tank position to be in full compliance with the laws in a no-discharge zone. It’s still up to the individual cruiser to obey the law and leave a clean wake. Another advantage to sending the sewage directly overboard rather than running all sewage through the holding tank before discharging it overboard is that this arrangement minimizes odors. We can pump our holding tank from deck, using a standard dockside or alongside pump-out, or pump the tank at sea — outside the no discharge zones — using the macerator pump.

All the plumbing is standard 1-1/2-inch except for the 1-inch macerator pump discharge. The lower port of the holding tank is connected to the 1-1/2-inch macerator pump input via a normally closed 1-1/2-inch in-line shut-off valve. The 1-inch output of the macerator pump is connected to an unequal 1-1/2-inch to 1-inch tee just inboard of the overboard discharge seacock. The unequal T-hose fitting is necessary to connect the 1-inch macerator discharge to the 1-1/2-inch overboard discharge. The unequal 1-1/2- to 1-inch tee is fabricated using a standard 1-1/2-inch nylon hose tee tapped on the side to 1 inch using a 1-inch pipe tap. A standard male 1-inch pipe to 1-inch hose fitting is threaded and cemented into the tapped side of the 1-1/2-inch tee. The macerator pump is connected via a heavy-duty, no-odor hose to the 1-inch port on the tee. When outside no-discharge zones, this arrangement allows us to flush the holding tank with either seawater pumped into the holding tank from the head or seawater pumped into the holding tank from deck using the washdown pump hose. The holding tank is then pumped overboard by opening the 1-1/2-inch in-line valve to the macerator pump and operating the pump until it runs dry. Boats with heads below the waterline will require a 1-1/2-inch vented loop to prevent seawater from siphoning into the head.

Dick and Kathy de Grasse live aboard their Tartan 34, Endeavour, in the winter and voyage in the Caribbean.

By Ocean Navigator