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​​Septic Tank Backup: Common Causes & Warning Signs

Every homeowner dreads the day when their septic tank backs up. This can be a costly and smelly mess, so it’s important to know what causes septic tank backups and how to prevent them. 

A septic tank backup can happen to anyone and is often caused by simple mistakes that could have been prevented. It’s critical to be aware of the red flags that indicate a septic tank backup.

In this article, we’ll talk about the common causes of septic tank backups and how to spot the warning signs so that you can take action before it’s too late. Let’s start by discussing how does a septic tank work.

How Does a Septic Tank Work?

septic tank system

A septic tank is a chamber used to treat wastewater from your home. It’s typically made of concrete, fiberglass, aluminum, or plastic installed underground. Septic tanks are usually used in rural areas without a central sewer system.

Wastewater from your home flows into the septic tank where it’s stored. The tank allows the solid waste to settle to the bottom while the lighter liquids rise to the top. This process is called separation.

The liquids that rise to the top are called effluent. The effluent is then pumped out of the septic tank and into a leach field, where it’s further treated. Bacteria break down the solids that settle to the bottom of the tank over time.

Now that you understand how a septic tank works let’s talk about the common causes of septic tank backups.

What Causes a Septic Tank to Backup?

Several things can cause a septic tank backup. Some of the most common causes include:

Improperly maintained septic tanks

a man pumping the septic

You will need to pump out your septic tank every 1-3 years to remove the accumulated solid waste. If you don’t pump out your septic tank regularly, the solids will build up and eventually cause a backup.

Tree roots

Tree roots can grow into your septic tank and clog the pipes. This is one of the most common causes of septic tank backups. When tree roots invade your septic tank and pipe, it can cause the tanks to crack and leak.

If you have this problem, you’ll need to have the roots removed. If you want to do it yourself, feel free to read our article about How to Kill Tree Roots in Your Sewer Line.

Flushing non-biodegradable items

non-biodegradable materials found inside the septic

You should never flush non-biodegradable items down the toilet. This includes diapers, feminine hygiene products, paper towels, and cigarettes. These items will not break down in the septic tank and eventually cause a backup.

If you have a septic tank, it’s essential to be mindful of what you flush. Only flush biodegradable items like human waste and toilet paper.

Clogged pipes

If your home has clogged pipes, it can cause wastewater to back up into your home and lead to a septic tank backup. If you have clogged pipes, you’ll need to have them cleaned out by a professional.

Improper Installation

If your septic tank has poor installation, it can lead to several problems, including backups. If you’re having septic tank problems, it’s important to have the tank inspected by a professional to ensure that it will undergo proper installation.


a flood causing the back up of a septic system

Heavy rains can cause floods. If there’s a lot of flooding in your area, it can overload the septic system and cause a backup. If you live in an area prone to flooding, it’s important to take steps to protect your septic system.

You can do this by installing a sump pump or raising the elevation of your septic tank. By this, we mean placing the tank on higher ground.

Now that you know the common causes of septic tank backups let’s talk about the warning signs.

Warning Signs of a Backup Septic Tank and How to Fix Them

Several warning signs indicate a septic tank backup. If you notice any of these signs, we recommend calling a professional plumber right away. Some of the most common warning signs include:

Bad smells

If you have a septic tank backup, you’ll notice an unpleasant smell coming from your drains or around your property. The build-up of sewage in the tank causes a foul odor. The odor is usually similar to rotten eggs.

If you are experiencing this problem, you can read our article about How to Get Rid of Smelly Drains For Good! to be guided on how to fix this issue.

Slow drains

slow drains in the kitchen because of backup septic system

It’s an indication of a problem with your septic system if your drains are taking longer to drain than they should. A build-up of solid waste usually causes slow drains in the septic tank.

You can try to fix this issue by using a drain auger or pouring hot water down your drain. If this does not work, then it would be best to call a plumber to clear out the blockage in your drain.

Gurgling sounds

If you hear gurgling sounds coming from your drains, it’s a sign of a clog. The air that is trying to escape from the drain causes the gurgling sound. Also, you will experience your toilet bubble when you flush if there is a blockage preventing proper drainage.

Overflowing toilets

overflowing water in the toilet caused by a septic issue

If you have an overflowing toilet, it’s a sign of blockage in your septic system. The blockage prevents the wastewater from flowing through the pipes and into the septic tank.

If you have an overflowing toilet, it’s important to stop using all the plumbing fixtures in your home. This includes the toilets, showers, sinks, and washing machines. By doing this, you can prevent the problem from getting worse.

Wet spots in your yard

wet spots in the yard because of backup septic tank

It might indicate an issue with your septic system if you see damp areas in your yard. The sewage leaks from the tank causing the wet spot in your yard.

If you notice any of these warning signs, you can diagnose the problem, or the most recommended action is to call a plumber to look at your septic system.


Septic tank backup is a serious problem that you should fix soon. By reading this blog, you now know the common causes of septic tank backups and the warning signs to look out for. Don’t hesitate to call a professional plumber right away if you notice any of these signs.

If you live in Lower Mainland Canada and experiencing any septic tank issues, please do not hesitate to reach out, and we will be more than happy to assist you. We offer both septic tank installation services as well as septic tank pumping services. Give us a call today for your septic tank needs!

John Relampago

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