My shower floor started yellowing right after it was installed. How do I get rid of this?

Q. I have a shower floor that has small stones of different colors and it is yellowing in 3 places. This started right after it was installed. Someone told me it was iron in water. How do I get rid of the yellowing? It's in the grout and on the top of the small stones.

A. Thank you for providing the photos. It's possible that this problem will only be resolved by tearing out the shower and installing new tile, but first, you can try testing the water for iron. You can buy an at-home test kit online or at your local home improvement store. If you find that there is high iron content in your water, the next steps would be to address the stains and install a water filtration system.

To address the iron stains, start by cleaning the natural stone using a product called Iron Out, available at most home improvement stores. This may not remove the stains completely, but if you see some improvement, this means you may be able to remove the stains using the poultice method. For more information about mixing and applying a poultice, including a How-To video, visit our Stain Management App.

Your poultice ingredients will be one part Iron Out, two parts diatomaceous earth, available at pool supply stores, and water. Mix enough water with the dry ingredients to create a paste with the consistency of peanut butter. Pre-wet the stained areas with water, and then apply the paste to the stains, overlapping to the surrounding unaffected stone by about one quarter of an inch. Cover the poultices in plastic wrap, and let them sit for twenty-four hours. Remove the poultices, and if any staining remains, repeat the process as many times as needed to completely remove the stains. You may also try allowing the poultices to dry out completely between applications.

If your water test did not reveal high iron levels, this is bad news. Marble or any light-colored stone with a high iron content should not be used in areas where water exposure is excessive, such as exterior environments or showers. When the iron in the stone is exposed to moisture, a process called iron oxidation, i.e. rusting, occurs. Another possibility is that poor installation caused moisture to collect and caused iron oxidation in the stone. Either way, a demo and reinstallation would be required.

In tricky cases like this, we always recommend you have your professional stone restoration contractor examine the stone before you make any expensive decisions. If you do not already have a restoration contractor, contact us. Each of our PRO Partner companies is vetted, has signed a commitment to professional integrity, and has earned the right to be designated as a Certified SurpHaces PRO Partner.