Should You Use Caustic Soda to Unblock Drains?

Conventional wisdom suggests that caustic soda can effectively unblock drains at a lower cost than specialised drain unblockers.

Growing 'Cleantok' trends online have featured influencers promoting aggressive drain-unclogging products and DIY methods for clearing sinks. Unfortunately, these approaches can often cause more damage than benefit.

In this article, the drainage experts at Lanes explain what to do if your drain is blocked, which DIY methods are the best to use in an emergency, and how to take care of your drainage system so that it stays in perfect working condition.

Caustic soda, also known as sodium hydroxide (NaOH), is a highly corrosive and strong alkaline substance. It is a white, odourless solid that can dissolve in water, producing heat in the process.

Why you shouldn’t use caustic soda as a drain unblocker

The first is that, because caustic soda is corrosive, it can damage your pipes and eat away at your drainage system at the same time that it is eating through blockages.

This can create far more significant problems later on. While a blockage can be annoying to deal with, fixing a leak or relining a pipe system is a much bigger job, and can be far more expensive, so it’s best to avoid any actions that could damage your pipes in the first place.

Because of this highly corrosive nature, caustic soda can also harm the person using it. You should always wear gloves when using caustic soda and ensure you only do so in a well-ventilated area.

If the substance gets stuck in your drains, it can release chemicals that are harmful to your lungs, and cause you burns if you breathe them in.

Caustic soda creates a chemical reaction that breaks down food, hair and other organic materials - the primary causes of many blocked drains.

Caustic soda reacts and breaks down these materials, clearing areas where they have built up and removing the blockage.

However, it is difficult to know how much caustic soda to use. Using a lot will fully clear the blockage but can release dangerous chemicals into your home.

Using a smaller amount will be safer but may not completely clear the blockage. This can be a serious problem and is another reason why caustic soda is not recommended for unblocking drains.

Once the blockage is cleared and water begins to flow down your drain again, it may appear that the issue has been resolved. However, larger pieces of food, oil, grease, dirt, or other materials that caused the blockage may have remained intact and been pushed further down into the drainage system. When this occurs, these materials can accumulate and form what are known as “fatbergs.”

What is a Fatberg?

A fatberg is a large blockage made of fat, oil, and grease combined with things that people incorrectly dispose of in their drains, such as food scraps, sanitary products, and more.

These substances combine and harden over time, and can become so large that they cause blockages in sewer pipes.

It is not only time-consuming, difficult, and expensive to remove these, but they can also cause significant problems within the water system in your area, and they are certainly best avoided.

As well as refraining from using caustic soda to unblock your drains, you should take care not to dispose of fat, oil, grease, food scraps or anything else in your drains, to help to avoid the growth of fatbergs.

Find out more about what you can and can’t flush down drains and toilets in our article, What can you flush down the toilet and drains?

How to tell if I've damaged my drain with caustic soda?

Signs that you may have damaged your drain with caustic soda include:

• Visible damage or deterioration of pipes such as cracks and leaks.


• Persistent clogs or blockages such as frequent overflowing.


• Noticing strange or foul odours coming from your drains.


• Unusual gurgling or bubbling noises coming from your drains or plumbing.

If you are concerned about a blockage and need a quick solution, the best way to approach this is to hire a professional like the experts at Lanes.

We can remove most blockages quickly and efficiently and ensure that the material causing the blockage is permanently removed from the system and disposed of responsibly, helping to avoid problems arising in the future.

We can also provide advice and guidance on effective maintenance habits that can keep your drains in good working condition for the future.

For more information on the signs of a blocked drain, you can read our article ‘Signs of a blocked drain’.

What are better alternatives to caustic soda?

Better alternatives to corrosive substances such as caustic soda and bleach include manual unblocking methods such as plunging.

For alternative and safer ways to unblock your drains, read our article on ‘How to unblock a sink by yourself’.

If you have a stubborn blockage in your drains and need help from a professional, call Lanes Drainage Services today on 0800 526 488.