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Silicone sealant - How to seal a bath, sink or basin

silicone sealant Whether you are doing a new bathroom installation or your existing sealant needs replacing, at some point using silicone sealant may be necessary. In this section we take you through the process of sealing a bath, sink, or basin. We also show you how to remove old silicone.
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safety first Take extra care when using sharp blades.
Silicone sealant fumes can be harmful, so do not inhale.

Silicone gun overview

To the right is a typical silicone sealant gun.

We have pointed out the main parts of the gun:
  • The trigger (A in fig 1.1)
  • The release tab (B in fig 1.1)
  • The pressure rod (C in fig 1.1)

Preparing the silicone tube

First, cut the end off the applicator nozzle (see fig 1.2).

Measure the gap/joint to be sealed and cut the nozzle according to the size of the gap.

For best results cut the applicator nozzle at a slight (30-45 degree) angle, this will allow you to keep the nozzle tight against where the two surfaces meet.

Then, trim the end off the silicone sealant tube with either a pair of sharp scissors or a craft knife. Attach the nozzle to the tube by screwing it clockwise onto the thread of the tube. Take care not to cross-thread it.

Loading the silicone gun

Press the release tab on the gun (see fig 1.3), and pull the pressure rod back to allow you to insert the silicone tube.

Load the sealant tube into the gun, then squeeze the trigger gently until the pressure rod goes into the base of the tube.

Keep squeezing the trigger gently until the rod makes contact with the diaphragm. Don't squeeze the trigger too hard or the silicone will leak out of the nozzle.

Removing Silicone Sealant

Removing old silicone sealant can be tricky depending on the surface. One method is to use the blade of a craft knife (fig 1.4).

Slide the knife blade behind and under the silicone with the blade against the surface. Take care not to scratch the surfaces.

After slicing the sealant at both surfaces, use the blade to cut the silicone into sections. Place the blade back under the sealant and then lift it away from the surface (see fig 1.5).


Grab the loose end of the sealant and pull it gently, you should be able to lift the section of sealant away fairly easily.

You can remove any remaining remnants of silicone by gently scraping it off with the knife blade. Try using the whole length of the blade and sliding it along the surface scraping the sealant as you go.

There are chemicals available to remove silicone but they can be very harsh. Visit your local DIY store for more details if you feel chemicals are required.

Applying the silicone to the surface

Always make sure that all surfaces are dry and free of any old silicone, debris or dust.

Sealing a bath
For best results, fill the bath with water before you apply the silicone, as some baths give slightly when they are in use. If you seal the bath without water in it, then when you use the bath, it may stretch the silicone and eventually lose its seal.
Applying the Silicone.
Position the applicator nozzle against the surface, then gently squeeze the trigger until the silicone starts to come out.

While applying gentle pressure to the trigger, move the applicator nozzle along the surface at a measured pace (fig 1.6).

Try to cover the whole surface in one stroke.

Putting a finish on the silicone sealant

The simplest way to get a nice finish is to use your finger.

Wet your finger first to stop the silicone sticking to it, use a bit of saliva or some washing up liquid. Run your finger along the sealant to leave a smooth even coat (fig 1.7).

(you can also use a piece of rubber pipe or similar object)
To remove the excess silicone from your finger, use a sheet of paper towel.

Trying to get silicone off your hands with water just makes things worse! Use soap and water to clean your hands only after you have got the majority off with the paper towel.