INSTALLING OF FRENCH OR SUB-SOIL DRAINS
[Illustration: FIG. 45.--Sub-soil drain.]
When a building is erected on a site that is wet or springy, some
means of carrying off the surplus water in the ground must be
provided for, or the basement of the building will be flooded with
water. For the thorough understanding of the methods employed in
laying a drain of this kind, I will go over it carefully and the
beginner can read it and then study it, and understand just how it
is done. A site may appear to be dry on the surface of the ground
and yet be very wet under the surface. If no information can be had
regarding the site, it is always well to drain the site if it is on
a slope or near a body of water and on the water shed of a river or
lake. If a building is a large one and the foundation goes down
very deep, the site should always be drained. The drain is laid
under the basement floor and around the outside of the foundation
wall on a level with or lower than the basement floor. The value of
draining a building site when the building is first started is very
often overlooked. The cost of the drain will be saved in a few
years as the basement will be free from all excessive dampness. The
expense of installing a sub-soil after the building is up and in
use is great as well as inconvenient. The drain is called "sub-soil
drain" on account of its location under the ground and on account
of its duty of taking off all surplus water that is underground.
With the surface water taken off by the surface drains and the
sub-soil drained by the sub-soil drains, a wet building site can be
made practically dry (see Fig. 45).
MATERIALS USED IN SUB-SOIL CONSTRUCTION.--The object of the drain
is to collect water and carry it away from the building by means of
pipes. Terra-cotta pipes, with or without hubs, are used.
Perforated tile pipe is sometimes used. This pipe is unglazed
terra-cotta pipe with 1-inch holes in the sides about 3 or 4 inches
from the center. These holes allow the surplus water to enter the
bore of the pipe and thus be carried off beyond the building site.
When the sub-soil of a small building needs draining, the trenches
made for the house drain and its branches are used as a drain in
the following manner: The trenches are dug deeper than is required
for the house drain. The trenches are then filled to the correct
level with broken stones. There is space between these stones for
the water to find passage to a point away from the building. When
this method is employed, some provision must be made to prevent the
house drain from settling. When locating the drain, we must
consider approximately the amount of water that is likely to be in
the soil and required to be carried off. If there is considerable
water, the pipes should extend all around the outside of the
building foundation wall, also a main pipe running under the cellar
bottom with six branches, three branches on each side.
If there is not a great deal of surplus water in the soil, the
drain around the outside of the foundation wall should be put in
and one drain line running through the basement will be sufficient.
LAYING THE PIPE.--The drain pipe should be handled with care, for
it is easily broken. The trench should be laid out and dug, then
the pipe can be laid in it with a grade toward the outlet or
discharge. If pipes with a hub on one end are used, the hub should
not be cemented. A little oakum is packed in the hub to steady the
pipe and keep sand out, the bottom of joint is cemented, a piece of
tar paper can be laid over the top of the joint to keep the sand
out. With joints made this way, the water can find its way to the
bore of the pipe and yet the sand will be kept out of the pipe. As
soon as the water gets into the bore of the pipe it has a clear
passageway to some discharge point away from the building. If tile
pipes without any hubs are used, some covering should be put around
the joint to keep out the sand and still allow the water to find
its way into the pipes.
DISCHARGE OF SUB-SOIL DRAIN.--The water that accumulates in a
sub-soil drain must be carried off to some point away from the
building. As the pipes are generally under the cellar bottom and
under the house drain, it is very evident that this drain cannot
discharge into the house drain sewer, directly. If the building
site is on a hill, the drain can be carried out and discharged on
the surface at a point that is somewhat lower than the level of the
pipe under the building. Where this cannot be done, it will be
necessary to have the different lines of pipes discharge into a
pit. The water is accumulated in this pit until it is filled, then
it will automatically empty itself as later explained.
PIT CONSTRUCTION.--The pit for the sub-soil water is constructed of
cement. A pit 2 feet square or 2 feet in diameter and 3 feet deep
will answer all requirements. A pit of this depth will allow a
pitch for all lines of pipe, and is large enough for ordinary
installations. The pit is built up to the surface of the cemented
floor of the basement and covered with a removable iron cover.
CELLAR DRAINER OR PUMP.--A cellar drainer is employed to empty the
above-mentioned pit. The cellar drainer works automatically. When
the pit is filled with water, the drainer operates and empties the
pit and discharges the water into a sink or open sewer connection.
When the pit is emptied, the drainer shuts off. The cellar drainer
is operated by water pressure. When the valve is opened, a small
jet of water is discharged into a larger pipe. The velocity of this
small jet of water creates a suction and carries along with it some
of the water in the pit. This suction continues until the tank is
empty. There should always be a strainer on the suction pipe, also
on the supply pipe, to prevent any particles of dirt getting into
the valve. The pipes leading to and from the drainer should empty
into an open sink where it can be seen. There is a possibility of
the drainer valve leaking and then the water pressure will leak
through it, causing a waste of water. If this leakage can be seen
where it discharges, then the trouble can be rectified. The cellar
drainer is connected directly with the water pressure and should
have a valve close to the connection to control the supply.