Is it worth bringing the fan pipe to a cold attic or are there enough air valves?
Good day. I’m building a private two-story attic type house and began to lay sewers. It came to a fun pipe. I have two bathrooms, located exactly one above the other. I think they bring them to a common riser under the roof. I have a small attic there (about a meter) near the ridge. And I wanted to ask if this pipe could be led along the rafters precisely to this cold attic and left there without being brought out. How justified is this scheme and will it work normally? Or maybe it’s better to completely abandon the fan pipe, replacing it with air valves near each toilet?
Pros and cons of venting to the roof
In your case, combining pipes into one common riser begs for itself. This is a good decision. But the conclusion only to the attic is not worth it. Although you will not use it (judging by the size), but the whole space smells like “aromas” of sewers and, most likely, the smell will be felt on the attic floor.
Such an installation is harmful to your roof. Warm, humid air will blow from the riser, which will begin to settle on the under-roof structures with weak condensate. So all the wood will become damp and gradually covered with fungus. And in winter, the settled moisture is converted into icicles and ice. Therefore, if ventilation is removed, then it is on the roof.
For normal ventilation, a pipe of 20-30 cm is enough. The higher you lift it above the roof, the faster it will freeze, because the air inside is warmer, and the temperature difference will lead to the formation of an ice plug. For the same reason, flyugs and deflectors are not placed on the pipe, which impede the release of warm air. It is not worth fearing that a small pipe height in winter will be closed with a snow cap. Due to the release of warm vapors, the snow in the hole will still thaw, creating a kind of funnel through which your sewer can "breathe".
Be sure to see how far your pipe will be from the ventilation outlets and the windows of the attic floor. Close should not be set, because it can suck in all the smells of the reverse draft into the house.
If your fan pipe is located on the opposite end of the roof, away from ventilation systems, then the smells of sewers will not pull back into the house
The option with air valves for a private house is also acceptable, especially if you have only one bath. Simultaneous discharge in both toilets will not give such a strong flow of water to disrupt the water locks, so VC can be installed. But if you have your own septic tank, then the smells of sewers without a fan pipe will be heard near it. In addition, the valves are not eternal, and if they fail, then the sewer odors will reach the house, until you replace the failed part. But it happens that the owners leave for a long time, and the siphon, blocking odors, manages to dry out.Imagine how the house will be saturated with stink, until the family returns from a long journey! It is very difficult to weather such odors.
A fun pipe is a more reliable option. As they say, installed once - and forgot forever.
