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 ...and thanks for stopping by. I'm Claire Douglas,  DIY and home interiors writer specialising in money-saving and creative home interior projects. I've spent years developing my 'bespoke on a budget' approach to DIY and home interiors and I love sharing all my tips and tricks in tutorials and posts here on my blog, in articles I write for some of the leading titles, in the press, on Instagram, Tiktok and my online course

  • Claire Douglas

How to replace old or mouldy bath sealant with ease

Updated: Mar 13

Reseal your bath by removing and replacing the bath sealant.

resealing a bath by replacing the mouldy bath sealant

Replacing old bath sealant is one of those home maintenance jobs where the thought of doing it is worse than the actual task. I usually put it off for a while, allowing the sealant to get to a state where it looks revolting, then carry out the replacement quickly and easily, realise it’s not actually a big drama, but learn nothing and repeat the same exact process in a few years' time!

After sharing a reel on Instagram about the process of removing bath sealant and replacing it with a fresh application, I received a load of messages from people saying that they needed to do this in their bathroom for their bath or shower tray but weren’t sure how or were worried about tackling it so I thought I’d write a quick blog post detailing the steps. 

Before we get into the ‘how to’, a quick note about the tools and materials I used and why.

You will need


  • Utility (Stanley) knife or Sealant remover tool I used a scalpel this time round, but any sharp knife will be fine as long as it can cut the seal of the existing sealant

  • Toothbrush I find an old toothbrush super handy but it's not essential, any scrubbing brush or scourer that can clean the surface where the old sealant was will be fine. Nothing so abrasive it could scratch the bath or tiles, though.

  • Caulking gun Necessary if you aren't using a product with a built-in applicator gun

  • Smoother tool (optional)


  • Sealant removal gel (optional)

  • Silicone sealant Choose a mould-resistant bathroom silicone sealant. I love this one from Unibond as it's so easy to apply without faffing about with a caulking gun. 

  • Masking tape To create clean lines with straight edges. This is optional but is a handy hack for anyone worried about applying bath sealant for the first time or who usually makes a big mess of it!

  • Old cloth or kitchen roll For cleaning up excess sealant.

  • White vinegar (optional)

  • Anti-bacterial wipe (optional)

1. Remove the old bath sealant

Removing old bath sealant with a scalpel
Removing silicone sealant from bath

A word of caution before you start this step - don't scratch the bath!

It's easy to get carried away removing the manky old seal and accidentally leaving irreparable scratch marks. Use a utility knife or a sealant removal tool to cut and remove the old sealant carefully. Be thorough in this step to ensure a clean surface for the new sealant. Clean the area with a damp cloth.

2. Clean the surface

Cleaning up after removing old bath sealant
Removed bath sealant

Some people advise wiping down the area with white vinegar to remove any residue and ensure a clean surface for the new sealant.

I don't usually find this necessary, as once you've removed the old sealant, scrubbed the area, and then dried, it's usually good to go. If you have mould under the old sealant, an additional white vinegar clean would be advisable. Read more on cleaning up bathroom mould here. 

3. Apply Masking Tape

Masking around a bath before applying new bath sealant

To create clean lines and protect surfaces from excess sealant, apply masking tape to the edges of the area where you'll be applying the new sealant. This is a handy hack to help you get started but not strictly necessary. 

4. Load the sealant gun

Loading a caulk gun for silicone bath sealant

Load the sealant gun with the silicone sealant cartridge. Cut the tip of the cartridge at a 45-degree angle, making sure the opening is the desired size for your application. Read more here about how to load and use a caulking gun. If you are using the Unibond self-applicator, then you won't need a separate cartridge gun. 

5. Apply the new bath sealant

silicone bath sealant

Hold the caulk gun /  at a 45-degree angle and apply a steady bead of sealant along the joint. Apply consistent pressure and move at a slow, even pace. Smooth the sealant with a caulk smoothing tool or your finger - some people suggest dipping your finger in soapy water or white spirit, or you can wrap an anti-bacterial wipe around the end of your finger to prevent the product from going on your skin. Previously, I've wrapped some cling film around my finger, which worked quite well or used the corner of a plastic sandwich bag too! Any of these tricks will ensure a neat finish. 

6. Fill the bath

bath tap running

This is quite controversial, but it's at this stage that I usually fill the bath with water. I know people are going to say that you should do this earlier, but I like to stand in the bath while I'm applying the new silicone sealant because I find it easier to get the best results up close rather than leaning over the bath and arm's length away. This is especially the case for the tricky bit behind the taps. You can, of course, fill the bath earlier if you prefer, as long as you do it before the fresh silicone has started to set, as it could pull the edge of the bath down slightly and ruin the tight seal you've just achieved. 

7. Remove the masking tape

Removing masking tape when resealing bath

Carefully remove the masking tape while the sealant is wet to ensure clean lines. This bit of the process is seriously satisfying!

If you used masking tape, there shouldn't be any excess sealant, but if there is, just wipe it away with an old rag.  

8. Leave to cure

Allow the new sealant to cure according to the manufacturer's instructions. This may take several hours to a day. Don't use the bath or shower until the new application has fully cured to ensure the best results and fully waterproof sealant.  9. Test the seal

Once the sealant has cured, pour water over the seal to check there aren't any leaks or points of failure. 

How to reseal a bath

And there you have it - fresh new silicone bath sealant to give your bathroom a lift.

Related posts

This is one of several bathroom DIYs that I've shared, see below for some related projects...

Thanks for reading, if you've found this useful, I'd love you to scroll down to the very bottom of the page and hit subscribe to join my mailing list. You'll receive a monthly newsletter with updates, DIY tips and tricks and discounts and offers too.


Kirsten Foster
Kirsten Foster

Why do you fill the bath as part of this process? If it affects the sealant shouldn't it be done before you apply the sealant?


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