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104
Drain Testing.—The test applied to old drains is Kemp's test, which consists
of phosphide of calcium and sulphide of allyl, which in the presence of
moisture and water decompose with phosphorescent combustion, giving off
dense white fumes of phosphide of allyl, having the pungent odour of garlic.
This test is not only an odour test but also a sight test, and therefore renders
the smoke test more or less unnecessary. The smoke test is, accordingly,
reserved only for very exceptional cases when testing above-ground drainage
such as soil-pipes, etc, separately. I may add that Kemp's test, as above
described, is much more penetrating than smoke, and will disclose defects in
moist ground, and also when the drain is fairly deep.
With regard to the water test, the late Mr. Rogers Field, than whom no one
had more experience, stated that a year or two after being laid, no drain would
stand the water test unless it were constructed in iron surrounded by concrete.
The water test in this Borough is, consequently, reserved mainly for new
drains, and in these cases the main drain, the branches, and the chambers are
thoroughly tested with water before being passed by the Inspector.
In my Annual Reports under the heading of Drainage and Sewerage, it is
stated each year, in detail, the mode of testing in six different circumstances
bv four differing processes; in fact, a comple analysis of the method adopted.
Also in my Annual Report for the year 1902, page 87, is a note upon the
method of drain testing, and the circumstances in which it is necessary that
the drains should be exposed for the purpose of ascertaining defects causing a
nuisance.
Drainage Bye-laws, regulating the size of Pipes.—Builders still continue to
complain that they are allowed to put up a 3½in. soil pipe and a 3½in. vent
pipe to ventilate a 4in. drain, but that if they ventilate a 4in. drain, not having
a soil pipe but a branch W.C. drain on the same level, they are compelled to
make the branch 4in. diam. and the vent pipe 4in. diam.
In other words if the vertical vent pipe is the continuation of a 4in. horizontal
drain it must be 4in. in diameter, but if to this vertical vent pipe a W.C.
is connected it becomes a soil pipe, and may, together with the soil pipe, be
reduced to 3½in. in diameter.
A soil pipe is a direct continuation and part of a drain, that portion which is
horizontal being called drain, and that which is vertical being called soil pipe,
so that a soil pipe is a vertical drain, and should be subject to similar
provisions.
The anomaly was typically apparent in the case of the Teachers' House at
All Saints School, Pancras Street, (see Plan No. 10270), where the Committee
declined to take any action against the builder for putting up a 3iin.
ventilating pipe to the drain, because the W.C. was on the basement level
instead of the first floor.
The continual irritation and annoyance caused by this anomaly is not
experienced by the London County Council but by the Borough Council, which
is the executive authority; and I feel sure that the London County Council
would rectify the wrong upon the representation of the sufferers, if sufficient
pressure were brought to bear.