Based on our experience in cleaning and restoring showers, the most common reason for recurring mold is related to shower drain weep holes. Invisible to the naked eye, there is often a puddle of water trapped beneath the tile with nowhere to go. To clarify, if you have a tiled shower floor, you likely have a weep-style drain. Ideally, any water that seeps below the tile should flow towards the drain if the weep system functions correctly. However, this is where problems arise.
We find that approximately 90% of weep drains are clogged due to builders applying hot tar during the shower's construction. This implies that your shower may have never drained properly. Additionally, clogged weep drains can result from bar soap residue and hard water buildup, leading to mineral blockages.
To identify other signs of a clogged weep drain, examine your shower floor. If you notice cracks in your tiles or grout lines, white minerals or calcium rising through the tile or grout, or wall damage outside the shower curb, these are all indicators of a weep drain issue.
