The connection shown on the sewer side of the main trap in Plate 24 is an excellent one, and is a practice now demanded wherever possible by many plumbing ordinances.

The chief value of such a connection is that it allows a cleanout to be used in the end of the Y-branch into which the main trap discharges.

This cleanout controls the straight run of house drain into the house sewer, and a considerable length of the latter, while the clean-out at the opposite end of the house drain controls that section of the drain, and the two cleanouts on the main trap complete the entire control of the house drain and house sewer.

Nothing can add more to the worth of the plumbing system than the intelligent and liberal use of cleanouts. The money invested in cleanouts is a good investment always, for their use often saves not only much annoyance, but avoids the breaking into pipes to remove stoppages.

Every trap on the plumbing system, with the exception of water-closet traps and other traps combined in the fixture itself, should be provided with a cleanout. All cleanout screws should be of brass. Cleanouts for use on soil piping are of two kinds, entirely of brass or having the body of iron and the screw of brass.

The latter is known as the iron-body cleanout. The threaded parts of cleanouts should have at least six threads, tapered, and of iron-pipe size. Cleanouts should be of the full size of the pipe or trap which they serve, up to a diameter of 5 in., and not less than 5 in. in size for larger traps.

Cleanouts should always be used in the ends of Ys into which vertical stacks connect, as shown in Fig. E, Plate 14, and in the ends of all horizontal branches of soil or waste pipes. Quarter bends being used on rain leaders, cleanouts used on their traps must be depended upon for cleaning purposes.

A cleanout should be used at each change in direction of horizontal piping. By this means each run of piping is fully controlled in the event of stoppage.

The cleanouts thus far mentioned are known as end cleanouts.

In long runs of horizontal waste and soil pipe it is often necessary to provide cleanouts at intermediate points. Special cleanout fittings are made for this purpose, into which the cleanout cover screws.

They should be placed not farther than 30 ft. apart, and a more liberal use of them can be made with advantage.

All cleanouts should be made tight with a gasket, and no clean-out depending on the use of putty for a tight joint should be allowed.

All cleanouts in main traps that are underground, or any other cleanout that is underground, should be made accessible by means of depressions in the concrete bottom, and cleanouts outside the walls of the house should be located in accessible manholes.

The gasket generally used on cleanouts is of rubber, and if the gasket has been in use for a considerable length of time, it is almost certain to be destroyed in removing the cleanout cover. If not destroyed, it is probable that it has become so hard and lifeless that, if again used, a tight joint cannot be made. Therefore a new gasket should be used on a cleanout whenever the cover is removed, after having been in use long enough to get into this condition.

Another form of cleanout, not extensively used, however, makes tight by means of a ground joint. The advantage of this cleanout is that it is free from the objectionable features incident to the use of gaskets. The ground joint is also often easier to open than the screw joint.

The foregoing remarks apply only to cleanouts used on the large drainage piping.

There are certain additional facts to be considered also, concerning cleanouts on other parts of the plumbing system.

Whenever brass and galvanized-iron pipe is used for waste purposes, cleanouts should be liberally used at points where a change in direction occurs.

All drum traps located under floors should have their cleanout covers flush with the floor, in order to make them accessible without the removal of flooring. Such cleanout covers may be concealed beneath nickel-plated covers or guards screwed to the floor. The cleanouts of all traps should be on the inlet side of the trap, and submerged wherever possible. Submerged cleanouts show an imperfect joint by leakage, whereas the same imperfection in the case of a cleanout not submerged might remain undetected for an indefinite length of time.

Cleanouts on fixture vents are demanded by the plumbing ordinances of certain cities, but in a vast majority of cases it is probably a practice which has little value. The reason for this is that usually use of the cleanout is by the inmates only, who know so little concerning the purpose of the vent and of the cleanout that it is almost never made use of. When there is a stoppage of the waste it makes itself known at once, but a stoppage of the vent opening is never known, and consequently the remedy, by means of the cleanout, never applied.