Does Caustic Soda Unblock Drains?

By - Max
04.09.23 12:58 PM

Sodium hydroxide (NaOH), commonly referred to as caustic soda or lye, is a chemical alkali compound with the ability to neutralise acids and dissolve in water. It is often used to manufacture cleaning products like soap and detergents. Caustic soda is also a popular DIY method for unclogging and cleaning drains. While it is often chosen as a cost-effective alternative to hiring professional drain unblocking services, there are potential drawbacks to consider.

The Risks

Handling sodium hydroxide can pose significant risks. Contact with bare skin, inhalation, or ingestion can result in painful burns, immediate vomiting, nausea, diarrhoea, and chest and stomach pain.


Inhaling this substance can also cause damage. When caustic soda reacts with water or other substances in the drain, it can produce harmful fumes that can irritate the respiratory system and present health hazards. It is crucial to ensure proper ventilation when working with this chemical.


Caustic soda used as a drain unblocker has been known to damage plumbing materials, particularly old or corroded pipes. In this instance, it is essential to understand the type of pipes in your plumbing system and their compatibility with caustic soda.


Improper disposal of caustic soda solutions can harm aquatic life and contaminate water sources. Adhering to local regulations for the safe disposal of caustic soda and its by-products is then of utmost importance.

Clean water draining through a plug hole.

In addition to these risks, there is the possibility that attempting DIY drain unblocking may pale in its effectiveness when compared to professional unblocking services. Depending on the nature of the blockage, caustic soda may not reach as far as expected, and without specialist CCTV equipment, it can be challenging to determine whether the chemical has resolved the issue, temporarily alleviated the blockage, or caused damage to hidden areas of the drain. This then opens the system up to repeated blockages in future, and if caustic soda is continually used on drains, it can have a corrosive effect that will damage the pipes in the long-term.

A small cup full of caustic soda.

The Alternatives

Before using caustic soda to unblock a drain, it is wise to consider alternatives. At Grey-Water, we would strongly advise hiring a professional equipped with the appropriate tools to address blockages. Our use of cameras helps locate the source of the blockage, and an industrial drain jetter will effectively remove it whilst safeguarding your pipes from harm.

For minor blockages that can easily be remedied, boiling water can sometimes dissolve grease build-up. Following this, a mixture of baking soda and vinegar poured down the drain, left for around 15 minutes, and then flushed down with more boiling water, can help to break down organic matter within the drain.

It is also pertinent to take preventative measures. Regularly maintaining drains using drain screens or guards to catch debris such as loose food and hair, avoiding pouring grease down plug holes, and periodically flushing drains with hot water to prevent build-up.