s.

_The Scent Test_ is made by putting into the pipes a certain quantity
of some pungent chemical, like peppermint oil, etc., the odor of which
will escape from the defects in the pipes, if there are any. Oil of
peppermint is commonly used in this country for the test. The
following is the way this test is applied: all the openings of the
pipes on the roof, except one, are closed up tightly with paper, rags,
etc. Into the one open pipe is poured from two to four ounces of
peppermint oil, followed by a pail of hot water, and then the pipe
into which the oil has been put is also plugged up. This is done,
preferably, by an assistant. The inspector then proceeds to slowly
follow the course of the various pipes, and will detect the smell of
the oil wherever it may escape from any defects in the pipes. If the
test is thoroughly and carefully done, if care is taken that no
fixture in the house is used and the traps of same not disturbed
during the test, if the openings of the pipes on the roofs are plugged
up tightly, if the main house trap is not unsealed (otherwise the oil
will escape into the sewer), and if the handling of the oil has been
done by an assistant, so that none adheres to the inspector--if all
these conditions are carried out, the peppermint test is a most
valuable test for the detection of any and all defects in plumbing.
Another precaution to be taken is with regard to the rain leader. If
the rain leader is not trapped, or if its trap is empty, the
peppermint oil may escape from the pipes into the rain leader. Care
must be taken, therefore, that the trap at the base of the rain leader
be sealed; or, if no trap is existing, to close up the connection of
the rain leader with the house drain; or, if this be impossible, to
plug up the opening of the leader near the roof.

Instead of putting the oil into the opening of a pipe on the roof, it
may be put through a fixture on the top floor of the house, although
this is not so satisfactory.

Various appliances have been manufactured to make this test more easy
and accurate. Of the English appliances, the Banner patent drain
grenade, and Kemp's drain tester are worthy of mention. The former
consists "of a thin glass vial charged with pungent and volatile
chemicals. One of the grenades, when dropped down any suitable pipe,
such as the soil pipe, breaks, or the grenade may be inserted through
a trap into the drain, where it is exploded." (Taylor.) Kemp's drain
test