How to Unblock Toilet Using Caustic Soda

How to Unblock Your Toilet Using Caustic Soda

Caustic soda can unblock your toilet in no time at all, but it should always be used with caution!

Before you start unblocking your toilet with caustic soda you should follow our tips on how to cure your toilet blockage below.

Tips Before You Start Working With Caustic Soda


Wear gloves while cleaning

Before you start working with caustic soda you should:

  •     Wear gloves – preferably chemical resistant gloves.
  •     Wear eye protection.
  •     Put a mask on.
  •     Open a window – work in a ventilated room, if possible.
  •     Keep kids and animals out of the way when working with caustic soda.
  •     Add caustic soda to water (don’t add water to caustic soda – makes it very hot).
  •     Clean up any spillages.


Although the points below may seem obvious, you should never, ever do these things when using caustic soda:

Do not touch your face

  •     Do not touch your face.
  •     Do not eat the caustic soda.
  •     Do not let children play with the caustic soda.
  •     Do not rush around when carrying the caustic soda and water mixture.
  •     Do not pour caustic soda straight into your toilet – this may cause an even bigger problem!



Step 1: Preparation

Caustic soda is a nasty chemical that can cause severe damage to you if you’re not careful with it. It’s very important that you prepare your caustic soda mixture in a safe space, where you’re not likely to be bumped by children or animals.

Take your time when using caustic soda!

Cleaning Gloves and Mask

What you need to do:

  1. Get yourself ready – pop your gloves, mask and eye protection on.
  2. Get a bucket ready – one with a lip is better and it’ll be easier for pouring the mixture out later.
  3. Locate and place your caustic soda in a suitable area.
  4. Work near a tap so you have access to water. 
  5. Open the windows and doors to keep the room ventilated.
  6. Make sure the toilet is clear and there are no obstacles in the way.
  7. Lift the toilet lid and seat up.

Move on to step 2 now.

Step 2: Preparing the mixture

Now you’re ready to prepare the caustic soda mix that will help to unblock your toilet.

Be very careful, you are working with a dangerous chemical form now on!

Here’s what you need to do:

  1. Fill your bucket up with 4.5 litres of water.
  2. Add 1 kg of caustic soda to the water.
  3. Watch as the mixture starts to bubble.
  4. Stir with a wooden spoon, if necessary.
  5. Fumes will be given off at this point, so don’t remove your mask.
  6. Don’t go too near the bucket – stay a safe distance away from it.

Move on to step 3 now.

Step 3: The unblocking

Your mix is ready to go. Now you need to move over to the toilet and start on the unblocking!

Here’s what you need to do:

  1. Slowly and very gently pour the mixture into the toilet.
  2. When the mix has been poured in close the toilet lid.
  3. Leave the mixture for an hour.
  4. Fill a bucket with hot water and pour this water into the toilet after an hour has passed.
  5. The toilet should be unblocked.
  6. Move on to ‘Step 4: Cleaning up’ now.
  7. If the toilet is still clogged, repeat step 4 in this list of steps.
  8. If the blockage continues repeat ‘Step 2: Preparing the mixture and ‘Step 3: The unblocking’.

If your toilet is still blocked after you’ve repeated ‘Step 2: Preparing the mixture’ and Step 3: The unblocking it might be worth calling in professional help.

Caustic soda is very strong, and it usually removes stains and unblocks toilets with ease. So if your blockage is still there it could be a different problem.

Wiping the toilet

Step 4: Cleaning up

Once you’ve finished unblocking your toilet you need to clean up. Give your toilet a wipe down with some family friendly cleaning products and make sure any spillages are wiped away.


If Caustic Soda Has Splattered Onto You

You need to act fast if caustic soda has landed anywhere on your person and you must call a doctor.

While you wait for the doctor you should:

Wash caustic soda off your skin by using water – no soap. Keep washing your skin until the caustic soda has gone.

Wash caustic soda out of your eyes by using water – no soap. Repeat this for 30 minutes and make sure the water gets into all areas of your eyes.

You should always wear gloves and a face covering when working with this product.



Caustic soda is a powerful chemical that can unblock a toilet with ease. However, you should always be careful when you use such a hazardous product.

Let us know how you get on in the comments below!



Where can I buy caustic soda?

Caustic soda can be bought from DIY stores. See our list of places you can buy it in the UK.

How can I stop my toilet from getting blocked up?

Here are some tips on how to stop your toilet from getting blocked up:

  •     Regularly maintain your toilet.
  •     Make sure your toilet’s internal system works properly regularly.
  •     Don’t put anything unusual down the toilet.
  •     Don’t go overboard with the toilet paper.
  •     Keep a plunger near your toilet to tackle smaller issues before they get bigger.
  •     Try not to use heavy duty cleaners.
  •     Don’t overlook problems – fix them immediately.
  •     Try a different toilet paper.

Caustic soda is another name for Soda Crystals, right?

No. Caustic soda is not another name for soda crystals. You can learn what soda crystals are in our guide.