Ask the Architect

Finding a leak in the shower

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Q. We had our master bathroom redone last year, and the shower is leaking into the room below. It’s so frustrating, because the contractor and plumber have been back, repeatedly, but can’t find the leak. We’ve finally decided to tear the shower out and do it again. I wish we didn’t have to, but we see no other choice, unless you have some idea how to avoid this.

A. There are only 30 or so places where a shower could leak. If you find 29 of them, you’re almost there, but that one little pinhole can elude you. Showers don’t have to leak. There’s no rule that says they have to, just a rule that says that if you hire an under-achiever, you get who you pay for. I’m frustrated for you, because I’ve seen thousands of pretty good, almost perfect installations. You need perfect, however, and nothing else works.

Just remember that all leaks start at a place where materials join together. They also occur where there’s a lack of redundant, backup material. Start with the most obvious place, the floor, where water lands, accumulates and, we hope, drains quickly. The longer the water sits, the more it can penetrate joints and openings. An undersized drain pipe or drain opening won’t accommodate all the water coming from high-volume shower heads, a common mistake. If the shower drain receptor, just below the drain cover, isn’t a double or triple cup, so that one can overflow into the one below, with a wide collar, or flange, that sandwiches the shower base or membrane, then leaking is common, especially if the water is standing because the drain can’t handle the volume of water. If the shower base is custom-made, formed by the walls and lined with various membrane overlaps, then those overlaps may not have been fully adhered, and there may not have been multiple layers.

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