If the waste pipe is being situated vertically right after a fixture trap, as being seen in the S-trap, then, this wastewater will continue to flow right after a fixture is being emptied and will then clear the corner or the trap. It is being caused by an air pressure on the water on the fixture that has been greater than a pressure of the air in its waste pipe. An action of its water discharging to a waste pipe will then remove the air from a pipe and thus causes the negative pressure in its waste line.
For the indirect case or momentum siphonage, a water flow will pass the entrance into the fixture drain in a waste pipe, then, it will take away the air from a fixture drain. It decreases an air pressure within the fixture drain, plus the whole assembly will act as an aspirator.
Back Pressure - The flood of water in the soil pipe will differ based on the fixtures that had been used. The small flow tends to cling to a portion of the pipe; however, the big ones from the slug of the waste when it is dropping. As the slug of water failed down the pipe, an air in the front became pressurized. When the pressure is building, this will seek for the escape point. The point is either the fixture outlet or a vent. When the vent is being plugged or there has been no vent at all, its only escape for the air is a fixture outlet.
An air pressure will force the trap sealed up the pipe to the fixture. When the pressure is just great enough, a seal will be blown out of a fixture totally. The large water flow passed through the vent will aspirate its water from a trap, while the water flow come up to the trap will blow the water away off the corner.
Vent Sizing – the vent pipe installation has been the same to the waste pipe and the soil. The similar fixture unit criteria had been used. The vent pipes of lesser than 1 and 1/4 inch in diameter will not be used. The vents that are smaller than the diameter seem to clog and will not perform its function.
Individual Fixture Ventilation – This kind of ventilation is just normal to use for drinking fountains, sinks, and with lots of fixtures that need ventilation. The air admittance valves had been used often in the solo fixtures.
Unit Venting – This type of unit venting system has been commonly used for the apartment buildings. This kind of system will save the best deal of space and money when the fixtures are being placed back to back in the different apartments. However, it does pose the problem when the vents are being undersized since they will aspirate the water from another trap.
Wet Venting – The bathroom fixture groupings had been commonly wet vented and that is, a vent pipe is also being used as the waste line.
Preparing Your Plumbing For Winter