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How To Vent A Washing Machine Drain Pipe

By November 3, 2021Plumbing
Washing machine drain pipe vent

Let’s say that you are hearing some noises from your washing machine and the floor begins to flood. You freak out so immediately you turn the water off. There is still water in the washing machine and the drainpipe seems clogged. You ask yourself, is my washing machine pipe drain vented or clogged?

How to vent a washing machine drain pipe? You will need to install a standpipe that connects to the P trap. The standpipe will then connect to the drain.

This is a great time to call out a professionally licensed plumber. Let’s take a look at what’s involved with a properly vented washing machine drain pipe.

Washing machine with water in it
Washing machine with water in it

How Washing Machines Drain

Believe it or not, your washing machine is a very complex system. Once the end of your cycle has occurred a pump forces the water out of the tub and into a washer drain hose. This drain hose curves upward towards a standpipe. The standpipe is located near the hot and cold water valves. Assuming that everything is working properly, the water will flow upward and out into the standpipe, which takes the water out to the sewage line.

If for some reason, you have a malfunction throughout this process, the washing machine will not drain and water could back up and leak onto your washroom floor.

Initial washing machine drain pipe hookups
Initial washing machine drain pipe hookups

What Is Needed To Vent the Washing Machine Drain

The majority of the time, what is needed for a successful working washing machine drain is as follows:

  • Standpipe-horizontal pipe from the drain to the washer that is angled 1/4 inch per foot toward the drain.
  • P-trap-necessary to ensure the water doesn’t stand still in. Also, creates a seal to sewer gases do not enter your home.
  • Venting standpipe-this is a straight pipe (usually vented through the roof) to vent sewer gases.
  • Cheater valves-creates negative pressure by opening up a valve to allow air into the line while water is flowing. Not legal everywhere, so be sure to check with your local building code before installing.

Overflow Prevention of a Washing Machine Drain

Following these preventative steps will reduce the likelihood of a washing machine drain overflowing:

  • Using a garment or lint bag can prevent the excess buildup of lint inside the drainpipes.
  • Inspect and clean the washer’s lint trap or filter.
  • Keep at least 1/2 inch between the drainpipe and discharge hose to ensure proper drainage.
  • Use proper detergents so that soap residue does not build up.
  • Clean the hoses and drainpipe often.

How Much Does It Cost

The cost varies depending upon your needs. If you just need to replace the drainpipe then you are looking at $230 to $1,140. Building permits cost $30 to $150. Then finally, you might need to replace the washing machine altogether. This cost for a new machine could range from $350 to $1,200 depending upon the size that you need.

Other Recommended Maintenance

While you are learning how to vent a washing machine drain pipe, you will want to consider inspecting other plumbing areas of your home. Various appliances have drain needs and should be inspected. Take a look at how to unclog your dishwasher drain. This will prepare you for some ideas on your washing machine drain pipe as well.

At the same time that you are inspecting a clogged dishwasher drain, you can also inspect your clogged garbage disposal. Often the garbage disposal and dishwasher clogs are synonymous. They do end up draining into the same P-trap under the sink. So, inspecting clogged garbage disposal is also a priority.

Also, if you have a septic, you will need to have it inspected at least once a year and pumped every 2-3 years. Here are some great recommendations to make sure that the septic passes inspection.

Lastly, there are building codes that need to be followed to ensure a successful washing machine pipe drain is vented properly. In addition, you will want to hire a professionally licensed plumber to confirm your pipe drain setup is safe for the washing machine to drain properly.

Washing machine drain lines
Washing machine drain lines

When Do I Call A Professional

If you hear your washing machine making noises, has a bad smell, or water is coming out, you need to contact a professional plumber. Taking care of any issues right away can often help save you money. The washing machine might require some added plumbing or cleaning of the drain lines. This can be difficult for the average homeowner to fix so calling a professional plumber is the safest thing to do.


When completing any plumbing upgrades or repairs, you must consult various professionally licensed plumbing contractors. You will first want to call on a few professionally licensed plumbing contractors to get quotes on the installation of a washing machine drain line vent. While you are doing that, you will also want to call on All Coast Home Inspections for a plumbing inspection in Houston, TX.

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