How do I remove stains on my grout in my bathroom?


I have a problem with stains on the gout in our bathroom that I used that was TEC 550. I have tried several sealers, the last I applied is 511 Impregnator Sealer. It was applied as per the instructions, and allowed to “cure” for 72 hours.

I have good water “beading”. But after 2 weeks …….gray-ish spots show up on the grout. I contacted the manf and they told me that the sealer contains NO anti-mold ingredients. I clean / scrub with Zep gout cleaner.

It takes pretty vigorous scrubbing to get the stains to come out. They come back quickly. If the links don’t work, I can send pictures, as well as pictures of the shower floor tile and the stains…… I am “happy” to start over with products you recommend……or if there is something else I need to do…….


ANSWER -  The TEC 550 Power Grout says it is a unique cementitious formula, and that its unique formulation is stain proof* and provides strong, color consistent joints free of efflorescence that is resistant to shrinking and cracking, and doesn't require sealing.  So you should not have any staining?  Apparently TEC is suggesting that you have a microbial growth (mold) condition that is causing the staining.

Typically cementitious grout is porous and more susceptible to staining and shade variation than an epoxy or urethane grout.  Staining and level of maintenance required to keep grout clean is always high and depends on the porosity and finished texture of the grout. The more texture the grout has the more it can trap dirt and the more difficult it is to keep clean.

Microbial growth can only develop and persist if there is a damp environment with some sort of organic food with a relatively low pH.  Cementitious grouts are high in alkalinity so it has a higher pH of about 11.  So that is not conducive to microbial growth.  If there is organic material trapped in the texture of the grout and the grout is persistently kept damp you can get microbial growth.  It shouldn't be too difficult to clean with a scrub brush and neural detergent or even slightly acidic.

If water beads up on the grout, and the grout doesn't darken, then it isn't getting wet.  So it doesn't seem likely that your staining is a microbial growth.

It is possible that the difference in grout color could be just shade variation from the way it was installed.  If grout dries at different rates or if excessive water is used during the installation it could pull color pigment out of the grout.  The only way to fix this condition is to use a grout colorant that is an epoxy where you can paint all of the grout joints with it.  It comes in many different colors and will act as a sealer.  It is a tedious job to apply it and it has to be done per the manufacturers' directions.

It is also possible the gray color grout is a stain from how the floor has been maintained.  Often grout on floor tiles when installed is one color, and eventually it turns gray.  This is because people will use mops to clean the floor and they don't change their mop water frequent enough or pick up the dirty water with a wet/dry vacuum or rinse the floor with clean water.  So they end up leaving dirty water on the floor that evaporates letting the dirt absorb into the grout.   It can be cleaned by using a neutral detergent or one of the tile cleaning solutions with a scrub brush on an extended handle.  Let the cleaning solution absorb into the grout for 5 minutes or so, then scrub, then pick up with a wet/dry vacuum, then rinse with clean water using scrub brush, and then pick up with wet/dry vacuum.  Then you can buff the floor dry with a lint free cloth. Let the tile floor and grout dry thoroughly, and then apply a penetrating sealer over the grout and tile.  Immediate wipe it dry with a lint free cloth to make sure none of the wet sealer remains on the tile surface.

For links to companies who produce and sell tile cleaners and sealers click on the following link:  Cleaners and Sealers.

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