Horizontal Vent Pipe In Attic

A full sized vent is a primary vent where the drain line transitions at some point and becomes the vent pipe that exits the roof.

Horizontal vent pipe in attic.

When that happens it can fill with rain water or condensation. Re vent pipes otherwise known as auxiliary vents attach to the drain line near your fixture as they run upwards and over the main vent. With horizontal venting you must follow specific guidelines to ensure proper venting. Horizontal venting in horizontal vent systems the vent pipe can slope away or toward the water heater.

You must start with a vertical run of stovepipe before making a 90 degree turn towards the wall. This allows flue gases to gain upward momentum before encountering restrictions. In many an older home this drain pipe is perhaps 4 inches in diameter and stays that size all the way through the roof. The top plate may be doubled meaning you have to drill through 3 inches.

Other vent pipes that are smaller may connect to this full sized vent and that s perfectly fine. Experienced home inspectors should be on the look out for these conditions. Ran across this situation today on a warranty inspection. If the vent pipe slopes away the drain port cap located where the pipe exits the water heater blower pipe coupling should stay in place and the slope has to have at least 1 8 inch per foot.

Another not so common way the vent can become clogged is when a horizontal section of the venting system itself inside the attic is sloped the wrong way. The vent runs horizontal for 20 25 feet across the attic to the vertical pipe that goes through the roof. According to the plans this should be more than enough space to allow a horizontal vent to pass over the peak and meet up with the main vent in the rest of the house which has a higher roof peak. They can attach right behind your fixture or horizontally to the drain line.

Most manufacturers suggest at least 12 inches of vertical run from the stove.