Soil And Waste Pipes And Vents Tests


The term "soil pipes" means pipe that receives the discharge from water closets. The size of a soil pipe for ordinary dwellings should be 4 inches.

Size of Soil Pipes


One to three closets—4-inch XX cast-iron.
Four to eight closets—5-inch XX cast-iron.
Eight to twelve closets—6-inch XX cast-iron.

There are cases when 3-inch XX cast-iron pipe is used, but the practice is not recommended.

The soil pipe should be well supported and held in place. The connection between soil pipe and closet should be of lead to allow for any expansion of settling that might take place.

Material of Soil Pipes.—Soil pipe in common use today is made of light cast iron, tar-coated, extra heavy cast iron uncoated and coated, galvanized wrought-iron pipe, and steel pipe. The best kind to use depends upon the job and place where it is to be used. All kinds of bends and fittings can be had in any of the above-mentioned materials. In choosing the material of the pipe that is best to use, the following points should be carefully considered.

  1. First, new work or overhauling.

  2. Second, temporary or permanent job.

  3. Third, construction of building.

  4. Fourth, amount allowed for cost of materials on job.

  5. Fifth, size of job, that is, the number of toilets.

  6. Sixth, size of chases and pipe partitions.

Location of Soil Pipe.—The location of the soil pipe depends to a great extent upon the location of the toilets. The soil stack should be located on an inside partition. The horizontal pipe should not run over expensively decorated ceilings unless run inside of a trough made of copper or sheet lead. As far as possible, the pipes should be confined, to runs short, and the number of bends reduced.


Soil-pipe fittings can be had from stock almost to suit the conditions. I will enumerate a few. The names of these fittings should be familiar to the mechanic so that when ordering he can give the correct name. 1⁄16, 1⁄8, 1⁄6, 1⁄4 bend, sanitary tee, tapped tee, side outlet fitting, return bend, cross branches, double Y, double TY, traps. The uses of these cast-iron fittings perhaps are obvious, but a word about the use of each one will be of service.

The 1⁄4 bend is used to change the direction of run of pipe 90°. A long-sweep 1⁄4 bend is used on work requiring the best practice. 1⁄8, 1⁄16, and 1⁄6 bends are used to change the direction of pipe 45°, 221⁄2°, and 162⁄3°. Two 1⁄8 bends should be used in preference to one 1⁄4 bend where there is sufficient room. Side outlet 1⁄4 bend is used for waste connection. They can be had with an outlet on either side of the heel. Their use is not recommended.

Return bends are used on fresh-air inlets. Tees are used for vents only. Ys are used wherever possible. The use of a Y-branch together with an 1⁄8 bend for a 90° connection with the main line is always preferable to a TY or, as they are commonly called, sanitary T. A tapped fitting gets its name because it is tapped for iron pipe thread. Tapped fittings are used for venting and should not be used for waste unless the tap enters the fitting at an angle of 45°.

These fittings and pipe are joined by first caulking with oakum and pouring, with one continuous pour, the hub full of molten metal. When cool, the lead should be set and then caulked around the pipe and around the hub.

The amount of lead and oakum required for various-sized joints is as follows:

Pipe size............. 2 3 4   5 6 8   10 12   15
Pounds of lead.... 11⁄2 21⁄4 3 33⁄4 41⁄2 6 71⁄2 9 111⁄4
Oakum (ounce)... 4 6 8 10 12 16 20 24 30

Rust Joints.—The plumber is called upon to run cast-iron pipe in places where lead and oakum will not be of service for the joints. In cases of this kind, a rust joint is made. This "rust" is made according to the following formula:

  • 1 part flour of sulphur.

  • 1 part sal-ammoniac.

  • 98 parts iron borings (free from grease).

This mixture is made the consistency of cement, using water to mix thoroughly and bring all parts into contact with each other. When it hardens, it becomes very hard and makes a tight joint which overcomes the objections to lead and oakum joints.


This pipe comes in about 18-foot lengths and fittings of the following makes and shapes, and their use is fully explained. The lengths of pipe come with a thread on each end and a coupling screwed on one end. The lengths come in bundles up to 11⁄2-inches and in single lengths over that size. Screw pipe fittings, it will be noted, are called by a different name than cast-iron ones. The fittings in common use today are the 90 degree ell, 45, 22, and 162⁄3. The Y and TY, tucker fittings, and inverted Ys are used in practically the same way as the cast-iron fittings. The 90 degree ell, 45, 22, and 162⁄3 are used to change the run of pipe that many degrees. All 90 degree fittings, ells, and Ts are tapped to give the pipe a pitch of 1⁄4 inch to the foot. It is better to use two 45 ells to make a 90 bend when it is possible.


Inverted Y.—The inverted Y is used in venting to good advantage. The use of these fittings is illustrated in the sketches.

Waste Pipes.—Waste pipes are the pipes that run to or convey the discharge of waste matter to the house drain, from wash trays, baths, lavatories, sinks, and showers.

The usual size of waste pipes is 2 inches. Waste pipes are made of the same material as soil pipe. Lead and brass pipe are also in common use. All exposed waste pipes in bath and toilet rooms are brass, nickel-plated. The waste pipes under kitchen sinks and wash trays are either lead or plain heavy brass. All waste pipes are run with a pitch towards the house trap and should be properly vented as explained under venting. The pipes should be easy of access, with clean-outs in convenient places. The waste pipes under a tile or cement floor should be covered with waterproof paper and a metal V-shaped shield over the entire length. If the waste pipes are over a decorated ceiling they should be in a copper-lined or lead-lined box. This box should have a tell-tale pipe running to the open cellar with the end of the tell-tale pipe left open. If waste pipes are to take the discharge from sinks in which chemicals are thrown, either chemical lead or terra-cotta pipe should be used. If terra-cotta is used, it should have at least 6 inches reinforced concrete around it and the joints of pipe made of keisilgar.

Size of Waste Pipes

Urinals................... 2 inches
Kitchen sink........... 2 inches
Slop sink................ 3 inches
Receptacles............ 11⁄2 inches
Bath tubs................ 11⁄2 inches
Lavatories.............. 11⁄2 or 11⁄4 inches
Wash trays............. 2 inches

Tell-tale Pipe.—The tell-tale pipe is a small pipe that extends from the trough, pan, or box that is under a line of pipe or fixtures to the open cellar. When water is seen running out of this pipe, it shows that a leak exists somewhere in the line of pipe that is in the box or trough. The use of this pipe saves the destruction of walls and ceilings.


Fig. 55.--Circuit vent. Fig. 55.—Circuit vent.

Vents are the most important pipes in the plumbing system. Modern plumbing successfully attempts to make living in crowded and thickly populated districts, as well as in isolated buildings, free from all unpleasant odors and annoyances. This could not be accomplished without the use of vents. Vents relieve all pressure in the system by furnishing an outlet for the air that is displaced by the waste discharged from the fixtures. Another of its functions is to supply air when syphonic action starts, thereby stopping the action that would break the seal of the trap under fixtures. The pipe extending from top fixture connection, up to and through the roof, is called the ventilation pipe. All vents that do not pass directly through the roof terminate in this ventilation pipe.

Fig. 56.--Loop vent. Fig. 56.—Loop vent.

To explain the use of vents, we might well start in the basement of a dwelling house. Suppose there is a set of wash trays in the laundry; the 2-inch trap of these trays should have a 11⁄4-inch vent pipe leading from the crown of the trap up along side of the stack. On the first floor a 11⁄4-inch pipe from the crown of the kitchen sink trap will lead into it. Here the pipe should be increased to 2 inches. On the second floor the 11⁄4-inch pipes leading from the lavatory and bath traps come into it. The vent stack now extends up into the attic and connects with the ventilation pipe. In a general way, the above is an example of venting. The old method of venting was very complicated and is almost beyond describing with the pen.

In common use today, there are several kinds of venting, namely: circuit and loop venting, crown venting, and continuous venting. The circuit venting, Fig. 55, is used in connection with the installation of closets. Take a row of toilets in which the waste connection of each closet discharges into a Y-branch, and there will be a series of Y-branches. One end of this series of branches discharges into the main stack while the other end continues and turns up at least to the height of the top of the closet and then enters the main vent stack. When this main vent runs up along side of the main stack and forces the vent pipe connected to the series of Y-branches to travel back, it is called a loop vent. This type of vent supplies air to the complete line of toilets and is very efficient.

Fig. 57.--Continuous vent. Fig. 57.—Continuous vent.
Fig. 58. Fig. 58.

Continuous venting, Figs. 57 and 58, applies more to fixtures other than toilets. A P-trap is used and enters a T in the stack. The lower part of the T acts as and connects with the waste pipe while the upper half is and connects with the vent pipe. A study of the figures will aid the reader to understand thoroughly the above explanations. In continuous venting the waste of the lowest fixture is discharged into the vent pipe and extended to the main waste stack where it is connected. This is done to allow any rust scales that occasionally drop down the vent pipe, and render it unfit to perform its duty, to be washed away into the sewer.

Crown venting, Fig. 59, is as its name implies, a vent that is taken from the crown of the trap, thence into the main vent.

Each one of these methods of venting is used and considered good practice, provided it is properly installed and correctly connected with the use of proper fittings.

Fig. 59.--Crown venting. Fig. 59.—Crown venting.

Things to Remember.

  1. First, venting is to prevent traps from syphoning.

  2. Second, also to allow free passage of air.

  3. Third, circuit vent—loop vent.

  4. Fourth, continuous venting.

  5. Fifth, crown venting.

  6. Sixth, ventilation pipe extends from the top of fixture through roof.