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

openings required in the preceding descrip-

tion. In this case you have no choice but to

Y or T the macerator pumpout off the same

pipe that leads to the deck pumpout. Regard-

less, keep the elimination of valves, Ts, and

Ys as one of your primary goals. The fewer

there are, the less the chance of clogs. It’s

not unusual to see “clever” piping arrange-

ments on some boats that have enough

valves, connectors, junctions, and loops to

serve as the cooling system for a nuclear re-

actor. They may be clever, but they will give

trouble in the long run.

Discharge Considerations

Be sure that the seacock exits below the

waterline. For reasons I’ll never know, a

builder I worked with once installed the dis-

charge seacock on one of my office’s designs

above the waterline. Even though we stood

on the foredeck and the outlet was near the

stern, and even though we were going at full

cruising speed during pumpout, the smell

while emptying was indescribable! Also, be

very, very sure that you have quick access to

the overboard pumpout seacock. You ab-

solutely must have a padlock that will secure

it in the closed position when you’re in no-

discharge zones (NDZs). There should be a

placard posted near or at this seacock stating

that overboard discharge of sewage is illegal

in coastal waters. If you fail to have these

items and are boarded for a routine inspec-

tion, you’re in for a hefty fine.

Vent Odors

Holding tank vents (Figure 21-6) are an-

other consideration. There’s only so much

you can do to minimize the odor from these.

Locate the vent opening as far from win-

dows, hatches, doors, and cockpits as you

can. The next step is to install a vent filter

such as made by SeaLand. These work well

at decreasing the smell and require that their

filter element be replaced only once a year, at

the beginning of each season. The only thing

to keep in mind is that these filters are rather

large (about 14 in. or 36 cm long). You need

space to fit them and room to access them

once a year to change the filter.

Pumping Sludge—Handling Sewage

Groco, ITT Jabsco, and others make fine,

reliable macerator pumps (electric pumps

designed to grind up and pump sewage). My

office has used them all successfully, but the

SeaLand T-series pump seems to have given

us the best overall service (Figure 21-7). For

pumping out holding tanks, you have two op-

tions: a macerator pump or a pump that will

pass solids. I generally lean slightly to mac-

erator pumps, which grind up the effluent

into a fine slurry. Whale, however, makes its

Gulper electric sanitation pump, which

passes unmacerated solids almost as large as

the 1^1 / 2 - inch (38 mm) hose diameter. Alterna-

tively, they make a manual, diaphragm waste

pump intended for the same use. Powered

macerator pumps must be monitored care-

fully during operation, however, since being

run dry will damage them.

Holding Tanks

Finally, you want to consider the holding tank

material and manufacturer. Aluminum can be

used for holding tanks, but adding chlorine

PART SIX:PLUMBING SYSTEMS WITH NOTES ON FIRE SUPPRESSION

Figure 21-6.
Holding tank vent
filter (Courtesy
Dometic)

Figure 21-7. T-pump (Courtesy SeaLand)