Definition

According to the definition already given, all pipes from sanitary fittings intended for the reception of urine and faeces may be regarded as soil pipes. The pipes from urinals are, however, generally known as waste-pipes, and it may therefore be more convenient to adopt this term, but it must not be forgotten that these pipes may become even fouler than soil-pipes and must be treated with at least equal care.

Connection With Other Pipes

Just as different kinds of fittings may be connected to one main waste-pipe, so different kinds of fittings may be connected to one main soil-pipe. No objection can be raised to a single soil-pipe serving both water-closets and slop-hoppers, provided that the traps are properly ventilated. Nor can there be much objection to connecting the single trap (3 in. in diameter) of a range of stall-urinals to the main soil-pipe, provided again that the trap is ventilated. But a single urinal-basin with small trap ought to be kept separate, as the seal of the small trap will almost inevitably be destroyed by the large and rapid discharges from water-closets and slop-hoppers, if all are served by a single soil-pipe. It is probably for this reason that the London County Council now requires every urinal trap and waste-pipe to be at least 3 in. in diameter.

Trap-Siphonage

Some experiments carried out by Mr. Hellyer are interesting in this connection. To the side of a stack of 3-in. lead soil-pipe about 91 ft. high, open at the top, and with the drain ventilated at a distance of 40 ft. from the foot, a branch-pipe was attached at the height of about 30 ft, To this branch-pipe traps of various kinds were fitted in turn, and each trap was tested by simultaneous discharges from four water-closets connected to the soil-pipe at various points above the branch. The total flush at each test was about fifteen gallons. When the branch-pipe was not ventilated, nearly every small trap fixed to the branch was siphoned out at the first discharge, including 1 1/4-in. and 2-in. "Bower" traps, 1 1/4-in. Dubois trap, 1 1/4-in. and 2-in. cast-lead siphon traps, 2-in. "Eclipse" trap, and 1 1/4-in. "Anti-D" trap. A narrow band D trap, measuring 1 1/2 in. between the cheeks, and with 1 1/2-in. outgo was unsealed at the fourth discharge. Larger traps gave better results, but were generally unsealed by a succession of discharges.

A second series of tests was carried out on exactly similar lines, but with the branch-pipe ventilated by a 2-in. pipe connected with the trap-ventilation pipes of the water-closets. This large ventilation pipe did not render all the traps proof against siphonage; a 1 1/4-in. Dubois trap was unsealed at the second discharge, a 2-in. half-S cast-lead trap at the fourth, a 2-in. Eclipse trap at the sixth, and a 1 1/4-in. anti-D trap lost 7/16- in. of seal in three discharges, but ten succeeding discharges had no further effect on it. A 4-in. Eclipse trap was unsealed at the tenth discharge, but twenty-two discharges failed to lower the seal of a 4-in. siphon trap more than 1/2 in.

These experiments show clearly the danger of connecting a small trap and branch to a soil-pipe serving a number of closets and slop-hoppers, although it must be admitted that the tests were much more severe than any likely to occur in the ordinary usage of the fittings. Cases may indeed occur where the choice must apparently be made between connecting a single urinal to a soil-pipe or providing a separate pipe of great length. The latter alternative involves a long pipe inadequately flushed, and certain to become coated with foul urates, while the former involves some risk of unsealing the urinal trap; but this risk may be reduced by making the urinal trap at least 3 in. in diameter, and by a proper system of trap-ventilation. In many cases, however, a third course is possible-namely, the fixing of a water-closet instead of the urinal basin. This will at once get over the difficulty, and will serve the purpose almost equally well if a proper type of closet is selected. Certainly this course is by far the best in private houses.

Arrangement

Pipes receiving the discharges from urinal basins only may be treated in the main as waste-pipes, but the pipes (including the trap-ventilating pipes) ought to be fixed outside the building, as the air passing through them is certain to be fouled by the accumulations of "fur." Whether the pipes ought to be disconnected at the foot or not, will depend upon circumstances and upon the local by-laws. In the London County, the waste-pipes from urinals must be treated as soil-pipes, and must not be disconnected from the drains. In the case of a single urinal on the ground floor, the arrangement shown for the sink A in fig. 196 is often adopted, although it is defective in making no provision for floor droppings. Where two or more urinals on different floors are connected to a main soil-pipe, the latter ought to be carried up as a ventilation pipe to a suitable point above the eaves, and the traps ventilated after the manner adopted for water-closet traps.

A range of urinal basins is sometimes treated in the manner shown in fig. 197, but with an additional ventilated branch and trap leading from the floor-channel which must be provided to receive droppings; part of the flush ought to be diverted into this channel in order to clean it and to keep the trap charged with water. Sometimes the traps under the basins are omitted, and the main waste is fixed nearly horizontal, and a standing waste-and-overflow is placed in a lead or brass tube beyond the last fitting, the top of the overflow being above the bottoms of the basins, so that water stands in these to the depth of one or two inches. The standing waste is under the control of the attendant, and when it is raised the contents of the basins and pipes are discharged through the single trap fixed below to the waste-pipe beyond. The dilution of the urine is the object of this arrangement, but the advantage in this respect is more than counterbalanced by the greater length of time during which the urine is in contact with the basins and pipes. Deposits of urates are certain to occur.

The pipes leading from ranges of basin-urinals are sometimes concealed behind the marble or slate backs, and cannot be inspected or repaired without pulling down the backs and basins. Damage to these will almost certainly result, but a still graver objection is that such an arrangement is directly opposed to one of the most important principles of modern plumbing, namely, that all pipes connected with sanitary fittings shall be exposed to view. For these reasons it is much better to adopt wastes of the kinds shown in fig. 146, discharging into a floor-channel from which a single trap and pipe are fitted. Exactly the same arrangement may be adopted for a single basin, the whole of the discharges passing through the floor-grate and trap. Diameter. - According to the By-laws adopted by the London County Council, the waste-pipes from urinals must be similar to those from slop-sinks. "An efficient siphon trap" must be fixed "immediately beneath" the fitting, and the internal diameter of the pipe must "not be less than 3 inches." The least weights of pipes 3 in. in diameter must be as follows:-

When two fittings are connected to one pipe, the traps must be ventilated in the manner specified for water-closet traps and soil-pipes.

The amount of water allowed for flushing urinals is so small that a long 3-in. waste-pipe from a single urinal cannot possibly be kept clean. If the urinal waste is connected by means of a short branch to the water-closet soil-pipe, this objection loses much of its force, but it is certainly a mistake to fix a long 3-in. waste-pipe from a single urinal flushed from a one-gallon cistern. Under such circumstances a pipe 1 1/2 or 2 in. in diameter would be more effectually flushed. "The Removal of "Fur." - The foul "fur," which is gradually deposited on surfaces to which urine is repeatedly applied, can be removed by means of "spirits of salt,"-an aqueous solution of hydrochloric acid. The time required will depend on the amount of fur and the strength of the solution. Lead is for all practical purposes unaffected by a cold solution, whatever the degree of concentration may be, but a strong solution acts on tin, and may therefore injure soldered joints. A weak solution is consequently preferable, and may consist of one table-spoonful of spirits of salt to a quart of cold water. The lower end of the pipe should be temporarily plugged, and the pipe then filled with the solution, and allowed to stand full for a night. The operation can be repeated till the pipes are clean.