Are Liquid Drain Cleaners Septic-Safe? Find Out Here


Liquid drain cleaners can be harmful to septic systems and are generally not considered septic-safe. Here’s a brief summary of why:

  • Chemical Content: Liquid drain cleaners typically contain strong chemicals, such as sodium hydroxide (lye) or sulfuric acid, which are designed to dissolve clogs. These chemicals can disrupt the natural balance of bacteria in a septic tank that is crucial for breaking down and treating wastewater.
  • Damage to Pipes: The harsh chemicals in drain cleaners can corrode and damage pipes, including the pipes leading to and from your septic system. This can lead to leaks or other plumbing issues.
  • Septic System Disruption: Pouring chemical drain cleaners down your drains can introduce toxic substances into your septic tank, potentially killing off the beneficial bacteria responsible for breaking down solids and treating wastewater. This disruption can lead to septic system problems and failures.

Instead of using liquid drain cleaners, it’s recommended to employ alternative methods to maintain your septic system.

Why Liquid Drain Cleaners are bad for A Septic System


 In a septic system, all the magic happens in the septic tank. When you flush a toilet or drain the sink, the wastewater flows to the septic tank where billions of microbes break down the waste.

The sludge settles at the bottom of the tank while clear water flows out into the leach field. The top of the septic tank is occupied by a layer of scum.

To keep this system working seamlessly, you need to have a healthy bacteria ecosystem inside the septic tank. Contrary to what some people say, the microbes are self-generating and you do not need to replenish them.

Actually, some of the companies telling you to replenish the bacteria are the same ones selling ‘septic safe’ drain cleaners. You however don’t need to do that.

What happens when you use chemical drain cleaners is that they kill the good bacteria in the septic tank, slowing the process of breaking down your domestic waste.

When that happens, the level of sludge inside the septic tank rises and 2 things will happen next.

  • The sludge will flow out into your leach field and clog the pipes meaning water can flow out.
  • Sewage will start backing up in your house.

Sewage backups are usually very expensive to fix but nowhere close to the cost of replacing a leach field. The cost of leach field replacement is anywhere between $5000 and $20000.

To save you all this trouble, I would recommend exploring other ways of unclogging sewer drains instead of using liquid drain cleaners.

The unfortunate thing is that drain cleaners that are genuinely septic-safe are less effective or/and take too long to work. What draws people to products containing bleach or strong acids is due to how fast they work.

How Do Chemical Drain Cleaners Work?

Before deciding to use any chemical drain cleaner, it is important to first understand how they work.  Let us do that now and see why they are not the best to use if you are on a septic system.

1. Caustic Drain Cleaners

Caustic drain cleaners are mild (in reaction) and this is where the so called septic-safe drain cleaners fall. Their active ingredient is usually sodium hydroxide also known as caustic or lye.

The reaction involves the drain cleaner giving an electron to the substance causing the clog in an exothermic reaction (a reaction that releases heat).

It is this heat that makes grease and other clogs thinner and therefore easy to flow thereby clearing the clog. The heat is known to deform plastic drainpipes and weaken metallic ones over time.

2. Oxidizing Drain Cleaners

These types of drain cleaners are not very different from caustic drain cleaners only that instead of giving an electron to the clog the take one from it. This is the process known as oxidation.

In most of the common oxidizing drain cleaners, the active ingredient is sodium hypochlorite (also known as bleach). They combine with water to release heat and in the process break down the clog.

3. Acidic Drain Cleaners

Acidic drain cleaners are the harshest and should never be used in a septic system. You can use caustic or oxidizing drain cleaners once or twice in a septic system and get away with it but not acidic drain cleaners.

Their active ingredient is usually a strong acid like sulfuric or hydrochloric acid. They work by creating hydronium ions which have a positive charge.

These ions react with electrons in the clog releasing heat which liquefies grease, wax and oils and thereby clearing the clogs. Stay away from these drain cleaners even if you are not a septic system.

Can I use Drano on a Septic System?


Drano is one of the most common chemical drain cleaner in the market and that is why I need to talk about it. It is even marketed as being septic-safe. Is it though?

To find out, you will only need to look at the chemical composition of Drano. You will notice that Drano is an oxidizing drain cleaner containing high levels of bleach, lye and aluminum.

What you need to understand is that even as little as 0.4 ounces of the drain cleaner is enough to kill the bacteria in the septic tank. Now imagine what will happen if you use the 16 to 32 ounces recommended by the manufacturer per clog?

Drano should especially not be used to unclog toilets since the heat released is sometimes enough to crack the porcelain. Read more on that in this post.

Septic-Safe Methods to Unclog Drains

There are several methods that you can use to unclog drains in a septic system. They include:

1. Baking Soda, Vinegar and Boiling Water

Vinegar and baking soda will clear most of the light clogs in drains though they take some time. Most folks prefer chemical drain cleaners since they are work almost instantly.

Baking soda is an alkali while vinegar is a weak acid but both of which are septic. They react together in a fizzing reaction and in the process break down the clog.

  • If you have standing water in the drain you need to unclog, you will first need to drain it. That will give the mixture a chance to work directly on the clog.
  • Pour 1 cup of baking soda in the drain followed by another cup of vinegar.
  • Wait for about 15 minutes as the 2 react together.
  • Dump about a gallon of boiling water in the drain and check if that unclogs it.

While baking soda and vinegar will break down the clog, the boiling water will melt it further and flush it down the drain.

Just be careful not to use boiling water in a toilet. It can cause sudden expansion and cracking of the toilet.

2. Plunge the Drain

A plunger is an effective tool in dislodging light clogs. It is actually the first tool you should grab whenever you have a clogged drain.

In order to unclog a drain using a plunger though, you need to do it right. That involves choosing the right plunger.

If you are unclogging a toilet, you need to use a flange plunger which is bell-shaped. That type of plunger fits properly at the bottom of the toilet bowl allowing it to seal around the outlet for maximum pressure application.

In all other drains, use a flat-bottom plunger. For sanitary reasons you should have a separate plunger for the kitchen sink only.

To plunge effectively, have some water in the drain you are unclogging. Ideally, the rubber cup of the plunger should be immersed in water to create a proper seal.

Start plunging gently to have the plunge properly engaged then plunge aggressively for a few minutes. Lift off the plunger and if the drain is still clogged plunge some more.

3. Use a Drain Snake

There are several types of drain snakes but the most common one is the one comprising of a flexible cable wound on a drum with a spring-like head and a cranking handle.

You usually stick in inside the drain and when you encounter the clog lock the cable and start cranking the handle. The head will either shred the clog into tiny pieces or hook it and pull it out.

One type of snake called a toilet auger is specifically designed to unclog toilets. Be careful when using it rest you scratch the inside of the bowl.

If you have a clogged bathroom sink or shower/tub drain, there are some zip tools (flexible cables which you can use to pull out the hair from the drain lines). Hair is the main cause of clogged bathroom sinks and tub/shower drains.


If you do not have that tool, grab a wire coat hanger and straighten it then make a hook on one end, use it to clean the drains then follow it up with boiling water.

4. Remove and Clean the P-trap


If you are dealing with a clogged kitchen or bathroom sink, one of the best methods to unclog them is usually removing and cleaning the P-trap.

The P-trap is the U-shaped part of the drain line underneath the sink. It holds a little amount of water at all times which prevents sewer gases from coming up to the house and also prevents solids from clogging the drain line farther away.

If you have a clogged sink, most of the time the clog is usually in the P-trap. By removing and cleaning the P-trap, you will have cleared the clog.

  • Start by clearing the area under the sink.
  • Place a bucket or pan under the P-trap to prevent water from spilling on the floor.
  • Disconnect the P-trap. Try doing so with your bare hands and only use a wrench if the connections are very tight.
  • Clean the P-trap as well as the connecting tee if you have a double-bowl kitchen sink.
  • Connect the P-trap back and check if that fixes the problem.
  • Flush the line with hot water

How to Prevent Clogged Drains

  • Never pour grease down the drain.
  • Avoid grinding foods that are not recommended for use in a garbage disposal.
  • Install a hair catcher in your bathtub/shower drain.
  • Don’t use the toilet like a trash bag. Only flush toilet paper.
  • Have your sewer line frequently cleaned/inspected. No chemicals will unclog a sewer line. If there are tree roots causing the clog the plumber will know how to cut them.

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