What is a standpipe behind washing machine?

Author: Laney Fritsch  |  Last update: Tuesday, February 24, 2026

A laundry standpipe is a vertical pipe that connects your washing machine's drain hose to your home's waste stack. Although it might seem convenient to hook up your washer to any nearby drain line, this shortcut often results in water overflows and worse—could introduce toxic sewer gases into your living space.

What is a standpipe on a washing machine?

The standpipe is designed to prevent water from flowing back into your washing machine. To function correctly, the standpipe should be at least 34 inches tall, measured from the floor to the top of the pipe. This height is key to proper water flow and preventing siphoning, which can cause the standpipe to overflow.

Do I need a standpipe for a washing machine?

Washers need an air gap, not a solid connection to the sewer. Usually that is in the form of a standpipe. But this arrangement is fine, too.

What is the standpipe used for?

A standpipe is a system of pipe that delivers a water supply for hose connections and automatic sprinklers in combined systems. Standpipe systems are typically installed vertically from floor to floor but are considered horizontal when two or more hose connections are installed on a single level.

How do I clear my washing machine standpipe?

Use a funnel to pour about a quarter of a cup of baking soda into the pipe. Next, empty a baster full of vinegar into the drain hose. Top tip: If the blockage is not completely gone, you can repeat the above process. Once you have cleared any debris from the hose, pour hot water in to flush everything out.

How To Install a Washing Machine Drain Stand Pipe - 2" Trap & Stand Pipe Height

How to get rid of washing machine standpipe smell?

Check the stand pipe: If the smell persists even after cleaning your appliance, consider clearing your standpipe. The pipe might be partially blocked. Use a drain unblocker to remove the build up of residue. Now you've got rid of the problem, it's vital to prevent the smell from coming back!

Why is my washing machine drain pipe backing up?

Washing machines overflow for a variety of reasons—the leading culprit, though, is a clog in the drain pipe. Lint and other debris come off of clothing during the wash cycle and are drained from the unit alongside the dirty water, potentially leading to clogs that can wreak havoc on your drain pipe.

Is it necessary to have a standpipe?

A Class I system is typically required in buildings that have more than three stories above or below grade because of the time and difficulty involved in laying hose from fire apparatus directly to remote floors. For these reasons, Class I standpipes are the required system in high-rise buildings.

Why is it important to empty the standpipe of water after using it?

All Standpipes and attached equipment must be properly maintained in order to minimise the risk of contamination, backflow and water leakage.

How much water does a standpipe hold?

The standpipe, with a diameter of 84 inches and a height of 20 feet, holds approximately 20,960 gallons of water when the level is at 16 feet deep.

Why is my washer standpipe overflowing?

Overfilled Machine

In the case of too much laundry, the greater volume of water required to wash it can more easily overwhelm the drain pipe, resulting in an overflow. This is most common in newer washing machine models with sensors to determine how much water is required for the clothes loaded inside.

What is code for washing machine standpipe?

804.1 Standpipe Receptors.

No trap for a clothes washer standpipe receptor shall be installed below the floor, but shall be roughed in not less than 6 inches (152 mm) and not more than 18 inches (457 mm) above the floor.

Should washing machine standpipe be sealed?

While sealing around the discharge hose will prevent gases from escaping the standpipe, it doesn't allow the necessary airflow into the standpipe during the draining process. This results in overflowing and possible flooding of the home and/or the siphoning of water from the washing machine.

What is the pipe behind the washing machine?

A washing machine drain pipe, also known as a drain hose, is a flexible tube used to expel used water from a washing machine to a dedicated drain system. The washing machine drain pipe is an essential component of any household laundry system, ensuring efficient and safe removal of water post-wash.

What are the requirements for a washer standpipe?

Older residential codes allowed for 1 ½” standpipes, but modern washing machines require a larger size. Your laundry standpipe must extend past your washer's overflow line, typically reaching a height of 30-36” or 18”-30” above the trap.

What is the purpose of a standpipe?

The standpipe extends into the building to supply fire fighting water to the interior of the structure via hose outlets, often located between each pair of floors in stairwells in high rise buildings. Dry standpipes are not filled with water until needed in fire fighting.

Why is it important to remove standing water?

Stagnant water can be dangerous because it provides a better incubator than running water for many kinds of infectious pathogens. Stagnant water can be contaminated with human and animal feces, particularly in deserts or other areas of low rainfall.

Can you drink water from a standpipe?

Public standpipes provide a safe treated water supply for households who need water for drinking and other internal use – such as cleaning and washing. To get large volumes of water from standpipes, see Water carters.

Does a washer standpipe need to be vented?

All plumbing fixtures—including washing machines—must be vented.

Where should standpipes be located?

Class I standpipe hose connections shall be provided in all of the following locations: In every required interior exit stairway, a hose connection shall be provided for each story above and below grade plane.

How does a standpipe drain work?

A standpipe is an open-ended, metal pipe that can be screwed into a basement floor drain to permit the flow of water back up as high as necessary, thereby delaying or preventing a basement flood.

How to clean a washing machine standpipe?

Depending on the configuration of your home, the drain pipe may be connected to a standpipe or a floor drain. Check for any visible debris or lint buildup in the drain pipe and remove it using a pair of pliers or a wire hanger. If the clog is still present, you may need to use a plumbing snake or auger to break it up.

Why is water coming out of the pipe behind my washer?

Behind your washer, there is a place where your drain hose runs into the wall. This pipe can become clogged causing water to back up and drip back down the hose and onto the floor. To fix this you will want to run a small snake down the pipe to clear any clogs.

How do I know if my washing machine waste pipe is blocked?

A common reason for a washing machine not draining is a blockage in the drain hose. This could be due to lint, debris, or even small items of clothing becoming lodged within the hose. To check for blockages, remove the drain hose from the drain outlet and visually inspect it.

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