en the largest boarding-house or country hotel is likely to
discharge. There is, however, a tendency in all house-drains to become
filled in the early part of their course by the accumulation of grease
and solid matters caught in the grease. Where no form of grease-trap is
used, there is a certain argument in favor of the use of six-inch pipes
for the upper part of house-drains. The use of a grease-trap, however,
should always be insisted upon; and with its aid these obstructing
matters will be retained, and the outflow may be perfectly carried by a
four-inch pipe.

So far as the public sewer is concerned, it makes little difference what
is the size of the house connection drain through the greater part of
its course; but the junction with the sewer should, under no
circumstances, where six-inch sewer-pipes are adopted, be more than four
inches. I should even insist on four-inch connections with an eight-inch
sewer. Through neglect, or by reason of improper management, many kinds
of rubbish find their way into house-drains; and a four-inch opening
will admit as many of these into the sewer as it will be able to carry
away. If, by reason of bad construction or neglect, an obstruction is to
be caused at any point, it should be in the drain, which the person
responsible for it must cleanse or repair.

The grease-trap referred to above may be any form of reservoir which
will retain the flow from the kitchen sink until it has time to cool,
when its grease will be solidified, and will float at the surface. The
outlet from this trap should be at such a distance below the surface of
the water, that there will be no danger of its floating matter passing
in with the discharge. A very simple device for this purpose is shown in
Figure 5. From a trap of this sort the flow is constant whenever
additions are made to its contents.

[Illustration: FIG. 5.--GREASE-TRAP. I, Inlet; V, ventilator; O,
outlet.]

[Illustration: FIG. 6.--FIELD'S FLUSH-TANK.

A, Receiver; B, grating; C, ventilator; D, siphon; F, entrance to drain;
I, delivery from sink.]

Figure 6 shows the invention of an English engineer, Mr. Rogers Field,
which has the effect of retaining all of the outflow from the kitchen
sink until it is entirely filled,--say thirty gallons. When filled, any
sudden addition of a few quarts of water, as from the emptying of a
dish-pan, brings into action a siphon whose entrance is near the bottom
of the tank; and this siphon rapidly