Can a Toilet Vent be Upstream? [Detailed Explanation]

Yes, a toilet vent can be upstream. While I answered this in a word, there are a lot of things you need to understand to have a better knowledge of this before you actually do any changes in your house.

In this article, I’ll be discussing everything you need to know about this topic so that by the end of it, you’ll have a better understanding.

can toilet vent be upstream

What is a Toilet Vent?

A vent is a hole that allows fresh air to enter or stale air or gas to escape, but what is a toilet vent?

A toilet vent, also referred to as a plumbing vent, is a vertical pipe that connects to the drain pipe in the exterior and runs through to the roof. It helps in regulating and maintain the air pressure in the toilet drain system.

As waste passes through the drain pipe, the air is drawn into the pipe through the toilet vent for smooth passage.

The toilet vent allows fresh air into the drain pipe to enable the waste to move smoothly and prevent clogging.

Likewise, as the drain pipe removes waste from the toilet, the toilet vent removes sewage gasses and unpleasant odors from the pipe. This inflow and outflow of air and gasses maintain proper atmospheric pressure in the drain pipe.

The toilet vent runs to the roof, where the gasses and unpleasant odors can easily and quickly dissipate.

Only air and gas move in and out of the toilet vent, and no water runs in the toilet vent. A toilet vent is needed in any toilet drainage system for the efficient removal of waste and wastewater.

Every house should have a well-built toilet vent. Any house without a properly cantered toilet vent may experience toilet issues like clogging, a backed-up toilet, an overflowing drain line, and so on.

It’s important to run the toilet vent through to about a foot above your roof. You may also run the vent inside the wall if possible but it must extend through the roof.

Can a Toilet Vent be Upstream?

Yes! A toilet vent can (and should always) be upstream. Moreover, upstream is the best direction for a toilet vent.

Upstream refers to the direction against the flow of water and waste in the drain pipe. When a toilet vent is upstream, it goes in the direction away from the drain pipe.

One of the main reasons for installing a toilet vent is to conduct sewage gasses away from the toilet instead of allowing them to escape inside the house.

Hence, running a toilet vent upstream to the roof is better than running it downstream to prevent sewage gasses and water from entering your home.

If the toilet vent is not installed upstream – away from the source – then it’s not installed properly. Most upstream toilet vents go vertically along the wall to the rooftop.

Downstream refers to the direction of flow of water and waste in the drain pipe. This means that the toilet vent is installed in the same direction as the drain pipe. Downstream toilet vents usually run horizontally to the drain pipe.

Running the toilet vent downstream is possible but you must install it above the spill line (flood level) of the toilet to work fine. Cantering the toilet vent about 6 inches above the toilet’s flood level is fine.

The spill level or flood level is the level at which the toilet begins to overflow.

However, the ideal way is to run the toilet vent upstream.


Installing a toilet vent is important for the proper functioning of the toilet and to prevent any unpleasant smells or gases from escaping into the house.

The vent should always be installed upstream, in the direction away from the flow of water and waste in the drain pipe.

If you have any questions or need help with installation, please consult a professional.

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