Bad Drains; and How to Test Them / With notes on the ventilation of sewers, drains, and sanitary fittings, and the origin and transmission of zymotic disease

by R. Harris Reeves

The cleaning out of 60 cubic yards of sewage and the removal of the old drains did not in the slightest degree diminish the nuisance inside the building, consequently the 15-inch drain on the opposite side of the building was stopped off at G and H, and in testing the detector was placed at G. This length of drain being 140 feet contained 1751098
1728 cubic feet of gas, and 4 gals. 4 pts. 8 ozs. of water thrown into the trap H should have lifted the liquid to the usual height in the detector. This and a similar quantity of water did not indicate any compression, but the discoloration of the reagent in the detector was much quicker than on the drain which was first tested.

The drain was then opened at I, dividing it into two sections, that from G to I containing 93 cubic feet. Testing this by 2 gals. 3 pts. 6 ozs. of water gave the exact rise in the detector, consequently the leaks and bad gas must be in the section from I to H. This was tested by a fresh reagent in the detector, when the speedy discoloration of the liquid indicated that the source of the poison was very near.

By a few piercings of the ground at K, by the iron rod or searcher, the drain was found, and by following the old drain the two cesspits and additional drains shown in Plate 3 were discovered, and about 150 loads of old putrid sewage had to be excavated and cleared away. The leaks which prevented the rise of the liquid in the detector were in the crown of the old sewage tank M, and the hot-water pipes of the heating apparatus running in an air-shaft just over it, the heat extracted the poisons from the sewage and distributed them into the ward.

The connections at K and N having been stopped up, the drain from I H was again tested, when it gave 36 cubic feet more gas space than there should have been in the drain. A few piercings of the soil at O led to the excavating of those old drains which are shown attached, and these being excavated and cleared away, and the connections to drains K, N, and O being stopped, the drain was again tested from I to H, when compression in the detector took place in comparison to the exact quantity of gas that should be by measurement in the drain.

In describing the method of testing drains as shown on Plates 1, 2, and 3, nothing has been mentioned as to the level to which branch drains to houses should be laid, or the method of testing them to ascertain their fall.

The fall given to branch drains should not be less than 1 in 100, but 1 in 80 is far preferable, and if the drains are laid to this level, water will flow easily through them, but should any part be laid out of a level the water would lay in them and thus give a less quantity of gas. Then when tested by compression to the capacity of the drain the lesser quantity would denote the nature of the dip.

When a plan of drains exists, as in the two cases shown on Plates 1, 2, and 3, the difficulty of testing them and proving their defects will not be as great as when no plan has been made. If no plan has been made or no record kept of them, it is best to make a rough plan of the building, fixing the positions of all inlets, their sizes and lengths, of branches to the drains on the premises, and also to lay down on the plan the length and size of this drain to where it reaches the extent of the property or joins the main sewer, opening the ground for testing in a similar manner to that described in Plate 1.

In testing pipes or sanitary fittings of any kind, leaks can be easily found by attaching the detector or pressure gauge to the most convenient part of the pipe or fitting, and when everything is sound care should be taken to flush all inlets at the same time, to ascertain whether the rush of water has any effect on the traps or water-seal. If the vibration in the detector or pressure gauge exceeds 2/10ths of an inch, a freer gas space must be provided, or the action of the water checked in some manner. Pipes, whether sanitary or otherwise, can be tested as to tightness in a similar manner.

Some modification may be necessary in testing large sewers or the drains of a district, but if the testing is performed in a similar manner to that adopted in the above case the condition of the drains and fittings can be accurately ascertained. The least pressure or suction on the traps of drains or fittings will be shown by the vibration of the liquid in the detector or pressure gauge when the water passes through the pipes with flushing.

The term “bad drains” is not exclusively confined to those drains that have leaky joints, or have an insufficient fall, or traps which siphon during the passage of the water, but may also be applied to systems of sewers in general. There are two points in almost every system of drainage that call for some improvement. The first is having the inlets at junctions where small drains join sewers at the side of the sewers. Thousands of traps are being continually siphoned by this cause as soon as the water fills the sewer above the inlet of the branch drain, as this, when filled with water only a short distance, forces gas through the weakest trap, and on the water and soil lowering itself in the sewer, this water acts exactly as the plunger of a pump and draws the water out of the weakest trap. This is often the one in the area or basement of the building, and to avoid this all inlets at junctions should enter the top of the sewers, not for the soil to drop down so as to cause the sewers to silt, but in an oblique direction with the sewage flow. The second point is in the ventilation of sewers, which is not an easy subject to handle.