Pittsburgh’s Trusted Plumber Offers Plumbing Drain and Vent System Tips Using Air Admittance Valves

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Pittsburgh’s Trusted Plumber Offers Drain & Vent System Tips Using Air Admittance Valves

Overview of Plumbing Drain and Vent System
The system of pipes and stacks carries waste-water to the main drain line, where it flows to the municipal sewage system or a septic system.

According to the most referred and Pittsburgh’s trusted plumber Mr Rooter, most codes will allow the toilet to be vented via the main vent. If local codes do not, then either add an individual vent through the roof or place an air admittance valve (AVV) in a box with a louvered screen above the toilet. It usually goes in the wall, but open to the inside of the room. With that said, Bob Beall, master plumber and owner of Mr Rooter Plumbing in Pittsburgh and Youngstown, says that careful planning is the key to a successful drain/vent system which carries waste and water out of the house and further prevents the entry of dangerous sewer gasses.

“The primary conduit for all this work is the main vent stack, a pipe usually 3-inch to 4-inch in diameter running through the roof,” says Beall.

One or more secondary stacks of smaller pipe (2-inch – 3-inch) act as branches of the drain/vent system and branch drainpipes, typically 1 1/2 inch to 2 inch, carry waste water from fixtures to a stack. “Older materials,” according to Beall, who offers free expert plumbing tips daily to consumers, “such as cast iron and galvanized piping, have gradually been replaced by plastic pipe, first a black-colored ABS, then white- or cream- colored PVC.” Beall also recommends that the homeowner always check with local building codes to make sure the materials being used are approved.

“The system of pipes and stacks carries waste-water to the main drain line, where it flows to the municipal sewage system or a septic system,” says Beall. Gravity makes the whole system work, according to Mr Rooter, but in order for the water to flow down at the correct velocity, all drainpipes must be sloped at a minimum rate of 1/4 inch per foot.

Mr Rooter Tip Of The Day: Principles Of Venting

Tip #1 For waste to flow in a drainpipe smoothly it must have an unrestricted air passage in front of and behind it. Otherwise the movement of the water would create a vacuum behind it and high pressure in front of it (pushing air bubble out the toilet), slowing or actually stopping the flow (and pulling water from the traps).

Tip #2 Vent pipes provide this open airway.

Tip #3 All drainpipes in a house must be connected to a vent pipe so that waste can be carried away efficiently without the problem of creating and air pressure wave ahead of the water flow or creating a vacuum behind it.

Tip #4 In some cases, drainpipes are connected directly to a main or secondary stack, which travels through the roof.

Tip #5 In others, the drainpipe is joined to a revent which travels up and over to join a stack vent.

WHAT CAN GO WRONG: Sometimes at the end of a run, it is extremely hard to get the drain line at the exact angle to glue it properly. In these situations, cut the pipe as you normally would and use a flexible coupling a few feet before the end of the run to change the angle by a few degrees. This is referred to as “bringing the pipes in line.”

Air admittance valves (AAVs) use the natural vacuum created by flowing water to open a valve and let air into the drain line, allowing waste water to flow smoothly. The valve closes immediately after drainage, preventing the introduction of sewer gasses into the room. AAVs can drastically reduce the number of vent pipes needed.
There’s A Reason They Call Us Mr.™

Debra Santavicca PR, SMM, WebIT
Mr. Rooter Media Center

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Rooter (Pittsburgh)

Robert A. Beall
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