The Golden State: Where & How to Live, Secure, Visit, Enjoy and Thrive in California
New Handy Site On Plumbing
A very good way is to connect the trap vent with the main line vent. When running the trap vents, as well as main vents, they should always be made to pitch upward at all points. A great deal of condensation and scale is forming in vent pipes and without a pitch to the pipe these cannot go back to the trap, where they will flow away through the waste. Trap vent should, as a rule, be of the same size as the trap. An exception to this is the vent from a water closet. Although a water closet waste is 4 inches, a 2-inch vent is enough. For a properly installed water closet the 2-inch vent is taken off from the top of the 4-inch horizontal part of the lead bend, extended above the closet and connected to the main vent. A very poor practice is to connect the vent to the vertical arm of the 4-inch bend, as paper, etc., is likely to collect about the entrance and in time close it.
An old fashioned way was to connect the vent to the horn of the closet, as found in wash-down closets. It is now forbidden in nearly all ordinances. The objection to this form is that a blow or settlement of the fixture may break the horn, as the vent pipe is rigid.
Water closets are not so easy to siphon, as it more difficult to create a vacuum in a 4-inch pipe than it is in a smaller one. Therefore it is not necessary to vent it under certain conditions, as when it is located close to a stack on the top floor.
Vents from a number of fixtures can be connected into one line with this line connected to the main vent, and is in many cases preferable to running independent trap vents to the main. If so installed, several vents enter into the branch that leads to the main vent. Therefore the size of the branch vent shall be increased. See Figure 13.
With a small number of fixtures such as found in the ordinary bath room the 2-inch vent from the water closet is large enough to receive vents from other fixtures.
The main branch vent pipe should always be placed and enter the vertical main vent above the top of the highest fixture to prevent it from acting as a watte or soil, should there be a stoppage in any part of the waste. When located at a distance of 8 feet or more from the main vent to which the trap vent is to be connected, vent should be carried independently through the roof or the main at a point above all fixtures. For long lines of vent the size should be increased one size, as, in long pipes, due to the friction, the delivery of fresh air is not as rapid as in a short run.
