Really. One stain line and you want to abort on the entire shower? Tough Love.

No, no, no. If you need a linen closet, then voice inside your head should say you got to many linens ...make it into a bookcase instead :))) Just kidding

Since marble is not good for showers, you better try to take out the rust first with CLR after leaving the shower to dry for at least 24 hours. Then you need to call back your installer and ask him to put 2 coats of sealer. You will have to seal it yourself at least once a year . Good luck!

There could not possibly be any worse advice than using a strong acidic cleaner on marble. Marble is calcium carbonate, and is *dissolved* by acids. That is what etching *is*. Using any acidic cleaner as strong as hydrochloric or lactic acid would be an even worse disaster than currently exists. It would damage marble so severely as to create a need for immediate replacement.

If you don't kow anything about stone then don't give advice. You could have just totally ruined some lurker's stone if they took that advice.

Just stop. Enthusiastic bad advice is still bad advice. There is no product that will successfully remove rust from marble without damaging it. Light surface contaminations can occasionally be honed from the surface, and then the entire stone be resurfaced. That is not what the problem is here.

Bad advice gets circled round and round. Retold so many times people start to believe it's true. We live in a world where people think it's OK to build showers and shower curbs with drywall as a backer board. Crazy.

Just was stumbled upon this post, at first for me it was looked very
familiar picture. Then I realized what it is the shower floor I have restored
recently (I am business), hello to rserpico/Rose ;).

So below the other pictures "before" and "after", it was removed by sanding out that build up, then marble polishing to original finish and re grouting affected lines.

I don't think it could be properly fixed by not professional, the marble under the buildup was deeply corroded and deep sanding was required. The grout was damaged too.

Here is the link for the service to solve similar issues: http://www.marblerestoration.us/shower-works.htm

How long before you think the problem comes back? The grout lines now look worse than before in the second photo.

The grout was just applied and still wet and looks darker, as you know it will need up to 24 hours to dry and cure. As I remember it was antique white or similar color. This project was included the grout repair not the entire floor re grouting, I fixed only damaged/stained/missed grout.

It is not possible to say for sure when it will appear again or will appear at all. I believe it is either hard water deposits (like on bottom of teapot) or kind of adhesive (or part of its chemical composition) what soaking up through the grout pores or micro cracks in grout.

I don't think it was happened in a few months, more likely it was little by little "growing" during a few years. Just my thoughts, I can be wrong.

@life4real: you will have better results if you post your own thread in the design dilemma side of things. "Other" is rarely visited.

"...Could someone please explain to me what is the right base for the floor and what kind of grout to use?..." - life4real

First thing is you best Soak Test your Marble Tile and do those basic checks.

Best base would be in my opinion a 2" Mortar bed reinforced with 16 gauge 2"x2" galvanized mesh and Laticrete's 3701 Mortar bed. Then Permacolour Grout also by Laticrete. I would set the Marble with Laticrete 254.

Not sure what someone else would do but this is how I would do it.

For my shower pan I would have a pre-slope, NobleSeal CIS, my extra drainage channels overtop of that and a Positive weep hole protector.

Flood Test is mandatory. All water should drain away after.

It would be even better to replace the Marble with porcelain tile.