Basement Floor Drain Backing Up When It Rains? (Possible Causes & Fixes)

Basement floor drains are necessary, but they can be a nightmare when they back up, especially when it rains. The only way around a basement floor drain that backs up when it rains is to install a sump pump. Whether it be installing a backflow valve or sump pump, let’s take a look at what you should do when your basement floor drain backs up due to rain.

Basement Floor Drain Backing Up When It Rains

When water is backing up out of your basement floor drain, it could be the result of many different issues. However, it usually isn’t the fault of the floor drain itself. A common time for back-ups is during heavy rain, but why is your basement floor drain backing up when it rains?

If your basement floor drain is backing up when it rains there’s likely a backup from the municipal sanitary sewer system. When it rains heavily, sewer systems can become overwhelmed with water, sending water back into your home through the basement drain. Install a sump pump to pump out the water, install a backwater flow valve, and cap the drain until you need it.

Many homeowners are not aware that it is their responsibility to maintain the pipes between your home and the city sewer main. If these steps don’t work for your problem, it would be a good idea to call the city.  Find out of this is a common problem in your neighborhood, and if so, the issue may not be your plumbing system.

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Issues With Basement Floor Drain Backing Up When It Rains

Water flooding your basement is not only a pain, but it can cause a lot of damage. The water can ruin floors and walls, wreak havoc on your furniture and carpet, and lead to bigger problems. Two major concerns are mold and electrocution.

Therefore, it’s essential to resolve the issue right away. Make sure to turn off the electricity before you enter a flooded basement. Then, after the clean-up, do a thorough check for any possible mold.

Additionally, a flooded basement often leads to losing valuable, sentimental items. People often store things like heirlooms, photos, and antiques in a basement. Therefore, you have even more of a reason to understand why the basement floor drain is backing up when it rains, so you can prevent it.

Possible Reasons For Basement Floor Drain Backing Up When It Rains

Before you can fix the problem, you need to determine what is causing it. When it comes to a basement floor drain backing up, several things can be to blame. Here’s a look at the most likely culprits.

Overwhelmed Municipal Sanitary Sewer System

In the case where water is coming up through the floor and sink drains in the basement, this is usually due to a problem with the municipal sanitary sewer system. As more homes in a neighborhood are built, this puts more strain on the city’s sewer system. This extra strain can cause it to get so high that the water starts to flow back into the homes.

As we experience heavy rainfall, this problem will only get worse. The worsening comes from the addition of new construction and more gutters directing rain towards the street.

Problems With The Sewer

Sewer water can also cause backups because of blocks in the system. This is caused by buildup and natural interference. Whether it be from grease and debris, tree roots, breaks in pipes, and saturated ground, these all add to the problem.

Typically, water coming up through the basement floor drain is indicative of a clog in the drain line. If there happens to be a clog in the main building drain and water is running down from an upper fixture, the water will come out of the lowest fixture. This is often the basement floor drain.

If your basement didn’t have a floor drain, the water would still back up out of the lowest fixture of the house. In most cases, it would be the bathtub, shower, sink, or standpipe.

Flooding in the basement as a result of backed-up sewer lines represents a major problem for homeowners. There is the possibility that fecal matter is flooding into your basement, which can cause a real health hazard. This becomes a major cleanup project and if this is happening, it is best to get the city involved.

Solutions To A Basement Floor Drain Backing Up When It Rains

The best way to clear a clogged drain is to have the drain line cleaned out professionally. If you want to tackle this job yourself, it is going to be a very messy task. Whatever is pulled out of the drain is going to be gross, which is the main reason people hire out this kind of work.

If you have an older home, it’s pretty standard to hire a drain cleaning service to come auger the drain lines every year. This will help to clear out tree roots and is good preventative maintenance practice.

You also need to take proper maintenance practices when it comes to keeping your lines clear. You can pour tree root killer down your toilets once a year, for instance. The issue is that even with these preventive measures, the problem oftentimes is out of your hands.

Install A Back Water Valve

While you may not be able to immediately pinpoint the weak link in this situation, there are other things you can do to stop the water from coming up through your floor drain. If you can’t prevent the issue from happening, you can still stop it from entering your home until a more permanent solution is found.

If you are unfortunate enough to have water coming out of your basement floor drain, you will have to use a backwater valve at the drain. Because this is not part of most municipalities’ plumbing code requirements, many homes may not have one of these already installed.

A backwater valve is a one-way valve with a flap that opens and closes, depending on the situation. When the flap is open it allows water to exit your basement. When water starts to flow back up the drainpipe and enter your basement, the flap closes and prevents this from happening.

It is important to perform regular maintenance on backwater valves, to make sure that they stay clear and free of any debris.

If you need to install a backwater valve into your house after it has already been constructed, it is a much bigger project. You will need to get a plumbing permit from your city and have a licensed plumber do that work. The plumber will cut a hole in the concrete floor near the floor drain in order to access the main sewer line.

They will then dig down to the sewer line and cut out a section in order to make space for the backwater valve. This can be a bit expensive, but it is well worth the time, hassle, and risk that you will otherwise experience without one.

How a Backwater Valve Works

A homes sewage system is designed to allow water and sewage to exit the home through the plumbing. A backwater valve stops the sewage from backing up and re-entering the house, in the case of an overloaded main sewer line.

If you have a backwater valve installed, you can see if it is working properly by looking through the clear cover on the access box.

Inside the valve is a flap that opens to allow water to exit the home and closes to stop water from backing into the home. They also allow for sewer gases to be vented so that they do not leak into your house.

On each side of the flap is a small flotation device so that when sewage starts to flow back into the house, the flap will lift up and close. Once the water starts to recede, gravity will take hold and allow the flap to fall back down. Now the flap is open and your basement is safe to drain.

DIY Options To Fix A Basement Floor Drain Backing Up When It Rains

You have a couple of other options for dealing with a basement drainpipe that floods if you are not ready for the expense of a backwater valve.

Sump Pump

The first and most obvious is using a sump pump. This will kick on when the basement starts to flood and redirect the water elsewhere. These can be noisy, and you will need to make sure that your sump pump can handle the amount of water that comes in. They will also need a place to redirect the water, such as a sink nearby.

There are manual and automatic sump pumps, in many different sizes and strengths. Finding out what will work best for you will depend on a variety of factors.

Plugging The Drain

Another option, though one that will require you to manually assist the basement floor drain when needed, is to put a plug in it. This will stop water from coming up out of the drain and whenever you need to use the drain, you just have to remove the plug.

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Is It Really The Basement Drain Backing Up?

Another possibility is your flooded basement isn’t from a backed-up drain. If this is the first time you’re discovering water in your basement, check for surface water issues first. There could be water draining near your home’s foundation walls.

Is It Surface Water? 

Try to assess where the water is coming from. If it is only coming from one spot or you only notice it near an exterior wall, surface water is more likely to blame.

Some examples of surface water sources are things like overflowing gutters that have become clogged with leaves and debris. It can also be from overflowing downspouts or downspouts that are too close to your house. Downspouts should extend a minimum of 10 feet from your home.

Also, check the slope of pavement and landscaping around your home. Over time, the ground can settle, and ow you might discover areas that slope toward your home instead of away from it.

There can also be cracks in the sealant between your home and the surrounding pavement. Or, if you have a water irrigation system, it should not be installed near the house. If it is, this could be a source of surface water issues.

Groundwater Issues And Drain System Location

If you discover no surface water problems, the subsurface groundwater could be under hydrostatic pressure. This causes water to push up through tiny cracks in the basement floor.

Another possibility is if your drain system connects directly to the city storm sewer system. This is especially the case if you have an older home with a basement below street level. Storm water can back up in the city sewer system and fill the perimeter foundation drain system.

This saturates the ground around the basement with water under hydrostatic pressure, which pushes it into the basement through hairline cracks. If you find this is the case, consult with a professional to install a perimeter drain system that can relieve hydrostatic pressure.

Related Questions

Does homeowner’s insurance cover basement flooding?

Most homeowner’s insurance will cover you in the case that your basement floods. Whether the water is sudden or accidental, this is part of the covered loss on most plans

Can I pour bleach down my basement drain?

Bleach should not be poured down the drain. It is a powerful, toxic substance that can react with other substances in your pipes, potentially release fumes. It can also create more of a problem and further plug up the system. Bleach will not help to keep drains clear or remove any buildup, like grease or hair.

How much does it cost to install a backwater valve?

If you are constructing a new home, it costs between $150 and $250 to install a backwater valve. When retrofitting, you will need to access the main sewer line. This can cost from $1,000 to $2,000, though some municipalities have subsidies to help with these costs.

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Sean Jarvis

Sean Jarvis is an interior decorator, writer, and expert handyman. Well versed in everything home improvement, he is a savant at manipulating words and spaces and upgrading everything around him. Sean specializes in writing concise guides about appliance repair and installation, home and lifestyle, and other residential projects.

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