IPS, with inlet sizes of 1 l/4, 1 l/2, 2, or 2 l/2 inches.
The 1 l/2-inch inlet trap is the one most commonly used
for lavatories. These fittings are made from brass and
are usually chrome plated. The lavatory trap acts as a
check valve for the drainage system. The water that
collects in the trap prevents se wage gases from escaping
through the drain into the compartment where the
fixture is located.
The deck drains shown in figure 15-20 are made
from brass, and have a 2-inch IPS outlet. These types
are used in tiled heads and washrooms. At shore
stations, however, a combination drain and P-type trap
made from cast iron is used extensively. It consists of
a drain inlet, a drain outlet, and a P-type trap, all cast in
one assembly, and with a clamping ring and a brass
strainer disk completing the unit. This type of drain and
Figure 15-19.--Lavatory traps.
trap assembly comes in two sizes. One has a 6-inch
Figure 15-20.--Typical deck drains.