all the cold, freshwater taps will have the
same top-quality drinking water. On very
large boats, you would have a main hot-water
and a cold-water line (or possibly two of
each, one leading forward and the other aft).
Piping to serve the individual fixtures is teed
off these main lines.
Draining Away—Handling Gray Water
Naturally, you need to direct all the water you
use overboard efficiently. Drains should be at
least 1-inch (DN 25 mm) diameter. Larger
sinks fit 1^1 / 4 - inch or 1^1 / 2 - inch (DN 32 or 40 mm)
drains. Some small sinks use^3 / 4 - inch (DN
20 mm) drains, but that’s a bit too small and
tends to get plugged up. I’m amazed at how
few sinks are fitted with U-traps. There’s a
good chance any boat you inspect won’t have
them. Not only do the U-traps help keep
things from escaping overboard, but the
water in the trap forms an air seal between
inside and out, which makes heating and
cooling more efficient. The U-trap also mini-
mizes back surges, which can generate small
geysers in the sink when a boat plunges
deeply. Indeed, though standard U-traps are
fine, I prefer a full circle of hose. It is reliable
and easy to install. If something such as your
wedding ring falls into the drain, you can shut
off the seacock and unscrew the hose
clamps. Your ring might still be there. All
these drains should exit below the waterline
and so must have seacocks and double stain-
less hose clamps (Figure 20-4).Shower Drainage and
Vented Loops
Shower sumps pose additional problems.
More than a few boats simply drain the
shower into the bilge. This is just awful. All
that soapy water, hair, and bits of skin swirl
around in the bilge, gunking things up andChapter 20:Freshwater Systems
Figure 20-3.
Freshwater
delivery piping