Ventilation, whether for plumbing fixtures or heating and cooling equipment, is vital to proper operation! Blocked plumbing vents can cause unpleasant odors to escape into the home, and can interfere with proper drainage. Blocked ventilation ducts for heating and cooling systems can cause a range of problems, including improper venting of noxious gases, improper fresh air intake, and decreased efficiency, which translates into higher operating costs.
Plumbing vents are connected to a home’s plumbing system and exit the home through the roof. These vents must be kept open to ensure that the plumbing system operates properly in a home. When the home’s plumbing vents are clear, gravity drains plumbing fixtures in a controlled fashion, leaving behind some water in each fixture’s trap. The residual water acts as a barrier between the top of the plumbing fixture (sink drain, bathtub drain, toilet bowl, etc) and the waste water pipe. This residual water prevents sewer gases from traveling “backwards” through the plumbing and escaping into the living space.
Organic debris from falling leaves and animal nests can cause a ventilation duct to become partially or completely blocked. In addition, prolonged below-freezing temperatures and increased snow accumulation can cause frost to build up on the plumbing vent.
The symptoms of blocked plumbing vents include the escape of unpleasant sewer gases into the home and drainage problems. When a plumbing vent is blocked, the drain empties completely or almost completely due to a phenomenon known as siphoning. When a drain siphons, the water drains with significant force, and the water that should remain in the trap is instead removed. Without the water in the trap, sewer gases can escape from the drain and foul the living space.
Usually a drain that is siphoning makes a significant amount of noise when water is present. Visually, you may also see a “whirlpool” created around the drain that allows the drain to admit both water and air into the drainpipe. In addition, an improperly vented drain will drain noticeably faster than one that is properly vented. Loud noises during drainage can indicate that a plumbing vent is blocked or partially blocked. The increased rate of drainage is due to the additional force that is pulling water through the drainpipe.
To correct a blocked ventilation pipe, manually inspect the vent and remove any debris that may have accumulated in the pipe. Do not cap or cover the vent stack, as they are required to remain open. If the vent is blocked due to frosting, you may not need to do anything special, as the first increase in temperature will melt the accumulated frost.
If your plumbing vent regularly frosts, you may want to modify the plumbing vent to widen out at the point of exit from the roof. Wider vent terminals tend to discourage complete frosting. Keep tree branches away from your roofline at all times to reduce the amount of organic debris that might accumulate otherwise.
If you have a blocked plumbing vent that you cannot clear on your own, contact us at Boston Standard Plumbing & Heating at (617) 288-2911 for assistance!
In my next post, I’ll discuss the importance of keeping ventilation pipes for heating and cooling equipment clear.
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