How far can a drain go before venting?

Author: Keshaun Towne  |  Last update: Tuesday, May 20, 2025

For a 1 ½-inc pipe the vent should be 42 inches away at the most while a 2-inch pipe must have a maximum distance of 5 feet. For pipes that have a diameter of 3 inches the distance is 6 feet and for a 4-inch pipe the most it should be away from the vent is 10 feet.

How far can you run a 2-inch drain pipe?

When builders look only at the table without reading the text, they find that a 2-inch-diameter drain can run a maximum distance of 8 feet to the vent.

What are the rules for drain venting?

In general, the vent should be as close as possible to the fixtures it serves. This proximity helps ensure the vent can effectively equalize air pressure and prevent sewer gas entry. However, there are some common guidelines to consider: The vent should be within 5 to 6 feet of the fixture drain it serves.

How far can a plumbing vent run horizontally without a?

The typical rule of thumb according to code requires you to run a horizontal pipe for no more than one-third of the total length. However, there are exceptions to this building code: If your minimum pipe size is increased by one pipe size, there are no maximum length limitations implied in the system.

How far can you run B vent horizontally?

The maximum horizontal length of a Type B double-wall connector shall be 100 percent of the height of the chimney or vent except for engineered systems.

How Far Should a Plumbing Vent Be From the Fixtures?

What happens if a drain is not vented?

When drain lines aren't properly vented, low pressure inside the pipe can suck water out of the traps, letting sewer gas in. Air pressure imbalances inside the drain pipe can restrict water flow and cause sluggish draining, often mimicking a partial clog inside the pipe.

How far can a trap be from a drain horizontally?

The vertical distance from the fixture outlet to the trap weir shall not exceed 24 inches (610 mm), and the horizontal distance shall not exceed 30 inches (610 mm) measured from the centerline of the fixture outlet to the centerline of the inlet of the trap.

Does every plumbing drain need a vent?

Yes, every drain needs a separate vent to ensure the plumbing works properly and waste is removed. What happens if a drain isn't vented? Without drain vents, gases build up in plumbing pipes and drains and keep water from flowing freely.

How long can a horizontal drain pipe be?

1 through 917.4. 3. Water closet connections shall be not greater than 4 feet (1219 mm) in developed length measured horizontally from the stack. Exception: Where the connection is made with a sanitary tee, the maximum developed length shall be 8 feet (2438 mm).

How far from a shower drain can a vent be?

UPC code, mim 2" drain for a shower and your mim distance for a trap arm to a vent is 5 feet, but most inspectors will allow 6 to 7 feet.

How many fixtures can be on a 2 inch vent?

Under the Uniform Plumbing Code, a 2" vent can handle 24 fixture units(F.U). In a residence, a lavatory sink= 1.0 F.U., bathtub/shower= 2.0 F.U. and a toilet 1.6 gallon or less= 3.0 F.U, greater than 1.6 gallon= 4.0 F.U.

Can a shower and toilet share a vent?

Yes, the toilet and sink can share the same vent, as can the shower. It's common to have one main vent pipe for multiple fixtures, although you might need a larger pipe. You should check with local building and plumbing codes to confirm you'll have adequate piping for your home.

Does a plumbing vent have to go straight up?

Vent pipes must be installed so they stay dry. This means that they should emerge from the top of the drainpipe, either straight vertically or at no less than a 45-degree angle from horizontal, so that water cannot back up into them.

How far can a p-trap be from a vent?

As long as your 2” trap arm doesn't exceed 60” from the vent tie in you should be good, which from the look of it you are good.

How far can a vent pipe be from the drain?

For a 1 ½-inc pipe the vent should be 42 inches away at the most while a 2-inch pipe must have a maximum distance of 5 feet. For pipes that have a diameter of 3 inches the distance is 6 feet and for a 4-inch pipe the most it should be away from the vent is 10 feet.

Does AP trap have to be directly under the drain?

Ideally, it should be as close to your shower inlet as possible. The further away the P-trap is from your shower drain, the easier it is for foul smells and drain bugs to make their way into your shower. Also, a P-trap for a shower must be at least 2 inches in diameter.

Can a shower drain have a 90 degree elbow?

Yes, you can use a 90-degree elbow in a shower drain to redirect the plumbing.

What are the rules for plumbing venting?

Hence, if the drain size is 4 inches (102 mm), a 2-inch (51 mm) vent is required. A 3-inch (76 mm) drain would require a 1½-inch (38 mm) vent. A 2-inch (51 mm), 1½-inch or 1¼-inch (38 or 31.8 mm) drain would require a minimum 1¼-inch (31.8 mm) vent, this being the minimum size allowed.

Can a washer and toilet share the same drain?

Your drains are connected – One of the main reasons your toilet gurgles when your washer machine drains is because your washer machine is connected to the toilet drain. This isn't uncommon. Your washing machine might have been placed in between your toilet and sewer stack.

What can I use instead of a vent pipe?

Air Admittance Valves, sometimes called Durgo Valves, are one-way air valves that can be installed instead of Soil Vent Pipes, or sometimes in addition to them, to help keep the pressure in soil and waste systems balanced.

Do horizontal vent pipes need to be sloped?

Vent and branch vent pipes shall be free from drops and sags and be sloped and connected so as to drain by gravity to the drainage system. Every vent shall rise vertically to a minimum of 6 inches above the flood level of the rim of the fixture being served.

Can multiple plumbing fixtures share a vent?

It depends on the distance between each plumbing. If they are too close to each other, they can share. If they are away from each other, vents are separated.

How far can a washer drain be from a vent?

The maximum distance between a washer drain vent and the drainpipe depends on pipe size. A one-and-a-half-inch drainpipe can be no more than 42 inches from the drain vent, a 2-inch drainpipe can be no more than 5 feet away, a 3-inch pipe can be up to 6 feet away, and a 4-inch pipe can be up to 10 feet away.

Previous article
Why does my sewer trap smell?
Next article
How to make your car AC compressor last longer?