Dave Gerr - Boat Mechanical Systems Handbook-How to Design, Install, and Recognize Proper Systems in Boats

PART SIX:PLUMBING SYSTEMS WITH NOTES ON FIRE SUPPRESSION

Nevertheless, seawater does contain impuri-

ties. It can deposit salt crusts and can cause

unpleasant odors in itself when retained in-

side the head system’s plumbing. The ultimate

in luxury is using fresh water to flush toilets.

These days, with watermakers and large gen

sets aboard even mid-size boats, and with the

thriftiest heads using 1.5 pints (0.5 L) per flush,

there’s no reason not to use fresh water for

flushing. Some electric macerator-pump toi-

lets have a selector switch that allows you to

use salt water on long passages and fresh wa-

ter inshore or at the dock. Once again, the

drawback is the complication of the added

plumbing and the electric and motor systems

required. If you have an electric outage or a

pressure-water-pump failure, you can’t flush!

Evacuation Head

or Height Limits

Don’t forget that all toilets are basically

pumping water (whether a conventional

pump or a vacuum). The limit of lift or head

for the best toilets is about 19.7 feet (6 m).

Be sure to consult the manufacturer if the

toilet will have to pump against a head much

over 9 feet (3 m). Note that some toilets are

rated on evacuation heights of no more than

just 3 or 4 feet (1 m).