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Grout pen shower

Updated: 21 October 2026

You are looking at stained shower walls, or the floor of the tray, and you would rather not rake the joints out. A grout pen shower job is fair on a sound, dry, glazed wall. It is a weak promise on a floor you stand on, and it does nothing for a leak or black silicone. Listings in the [Grout pen](/hub/flooring-tools-and-accessories/grout-pen) set, captured on amazon.co.uk on 19 October 2026, often print “shower” without separating wall from floor. How to draw the line is on [how to use a grout pen](/hub/flooring-tools-and-accessories/grout-pen/sub/grout-pen-how-to-use). Colour and pack stay on the [grout pen buying guide](/hub/flooring-tools-and-accessories/grout-pen/sub/grout-pen-buying-guide). Peter F. scored these listings, not a lab, and amazon.co.uk links may earn a commission.

You are looking at stained shower walls, or the floor of the tray, and you would rather not rake the joints out. A grout pen shower job is fair on a sound, dry, glazed wall.

Our top picks

UniBond UniBond grout reviver pen, white, pack of 3

Best overall

UniBond UniBond grout reviver pen, white, pack of 3
8.7/10about £12.60
View offer
QHSXMQ QHSXMQ white grout pen, 8 with spare nibs

Best value

QHSXMQ QHSXMQ white grout pen, 8 with spare nibs
8.7/10about £5.99
View offer
Flintronic Flintronic light grey grout pen, 10 pack

Alternative

Flintronic Flintronic light grey grout pen, 10 pack
8.1/10about £8.98
View offer
On this page
  1. 1.Shower walls are the fair case
  2. 2.Shower floors wear the coating off
  3. 3.Mould and silicone are not the same stain
  4. 4.Aftercare and when to stop

Shower walls are the fair case

A glazed wall joint that is firm, clean and fully dry is the fair case. UniBond sells a water-based waterproof coating with a fungicide for vertical joints, and calls it a mid-term cover. The three-pack repeats about 60 minutes and about 60 metres on a 2 mm joint. A retailer quoting the label limits that pen to fully glazed wall tiles. Test a corner before you do the whole wall.

Shower floors wear the coating off

You stand on a shower floor, and the water sits longer than on a wall. Bromley Tilers say a pen there, or on a busy kitchen floor, wears off in patches. A waterproof claim is about the coating resisting water, not about feet. DRTRU names a shower stall and says waterproof, while reviews still say the liquid follows gravity. Flintronic’s attribute says water resistant, while a bullet talks as if caulks were waterproof. Read the attribute when the lines disagree. If the floor grout is cracking, rake it out and regrout. CG2 W is a grout class, not a rating for a marker.
UniBond UniBond grout reviver pen, white, pack of 3

Testsieger

UniBond UniBond grout reviver pen, white, pack of 3
8.7/10about £12.60
View offer

Mould and silicone are not the same stain

Light yellowing you can scrub back to bare grout is the stain a pen might cover once the joint is clean and dry. UniBond’s fungicide is a claim on that pen. It does not mean every pack that says mould resistant names an active, and it does not stop a leak. Black growth at the tray or bath edge is often silicone. Bromley Tilers say to cut that seal out, not draw over it. If mould returns in the same spot after a proper clean and dry, assume water is getting in. Bleach, if you need it, comes before the colour, then a rinse and at least two hours of drying.

Aftercare and when to stop

Follow the dry time on the pen you bought before you shower. UniBond’s claim is about 60 minutes. QHSXMQ has no dry time and no waterproof attribute, so do not treat a kitchen photo as a shower test. Avoid strong tile cleaners on a fresh line. On a sound glazed wall, the choice between the UniBond three-pack and the cheaper white eight-pack is on the best grout pen page. For the tray floor and for silicone, leave the pen in the drawer.

Common questions

Can I use a grout pen on shower walls?
Yes, if the tiles are glazed, the grout is sound, and the joint is clean and dry. UniBond aims the pen at vertical joints and states a waterproof coating after about 60 minutes, which is the brand’s claim. A retailer quote of the label limits that product to fully glazed wall tiles. Other packs mention showers in a bullet. Test a corner before you do the whole enclosure, because white can look too bright on aged grout.
Can I use one on the shower floor?
A shower floor is a poor bet. Bromley Tilers say the coating wears off in patches where you walk, and the same warning applies to a busy kitchen floor. Waterproof wording does not describe foot traffic. If the floor grout is still sound and you want a larger-area colour, look at a brush-on colourant and its own waiting time. If the grout is cracking or missing, regrout rather than draw over it.
How soon can I shower?
Use the time on the pen you bought. UniBond’s listing and brand page point to about 60 minutes, and Metro repeated that brand line. DRTRU says touch-dry at 30 minutes and to allow two hours. Peaflew says 30 minutes to touch and two hours to bond. Packs with no dry time in the file, including QHSXMQ, do not inherit the 60-minute figure. The joint also needs to have been dry before you started, which Homebuilding puts at two hours after washing.
Will it stop black mould?
It will not stop mould that is fed by a leak, and it will not fix damp behind the tile. UniBond states a fungicide on its own pen, which is a mid-term claim, not a permanent kill. Many other listings say mould resistant and name no active substance. Clean light staining, dry the joint, and coat it only if the grout is still firm. If black growth returns in the same place, call a tiler and look for water getting in.
Is the black line at the tray grout or silicone?
The soft bead where the tray or bath meets the wall is silicone, not the cement grout between tiles. Bromley Tilers say to cut that out and reseal it. A pen drawn along silicone cracks when the seal flexes and the black shows through again. The hard lines between the tiles are the grout. Only those, and only if they are sound, are a pen job.
Can I scrub with bleach afterwards?
Avoid chlorine bleach on a fresh coating. It can lift the colour, and over time it is harsh on cement grout. One Flintronic review tied a three-month result to staying off bleach cleaners. AOOSU’s listing says to avoid strong tile cleaners. Use a mild cleaner and a soft cloth. If you must bleach to remove growth, do it before you colour the joint, then rinse and dry.

Related pages

Grout pen vs grout paint

Grout pen

Best grout pen: UniBond three-pack or white spare nibs

Grout pen buying guide: joint, colour, nib, and price

How to use a grout pen on clean, dry bathroom joints

Sources

Public UK sources used for this comparison. Listing prices, stars and review counts are the amazon.co.uk figures saved for these 12 ASINs on 19 October 2026.

  1. UniBond Triple Protection Grout Reviver Pen (retrieved 19 October 2026)
  2. UniBond label details via McGrocer (retrieved 19 October 2026)
  3. ASDA: UniBond grout reviver pen 7 ml (retrieved 19 October 2026)
  4. Consumer Rights Act 2015, section 9 (retrieved 19 October 2026)
  5. HSE: Treated articles (retrieved 19 October 2026)
  6. Bromley Tilers: How to clean grout (retrieved 19 October 2026)
  7. Homebuilding: Cleaning grout (retrieved 19 October 2026)
  8. Ideal Home: Grout colouring with a grout pen (retrieved 19 October 2026)