Efflorescence is a pretty word for an ugly problem. Chemically speaking, efflorescence means "flowering out" and refers to loss of water of crystallization from a salt into the atmosphere after exposure to air. Efflorescence looks like a white, powdery, fluffy deposit on surfaces like brick, clay, concrete, and tile. Water dissolves salts inside the masonry while moving through it. Afterwards, it evaporates, leaving salt on the masonry surface. You've probably seen efflorescence on a large scale in parking garages, and other concrete structures, where it looks like trails of white crystalline material left behind when water evaporates.

If you notice efflorescence in your shower or bathroom, it may be due to tiny hairline cracks in your bathroom tile. Masonry building materials can be protected against it by treating them with a sealer that impregnates the material and repels water. Sometimes efflorescence is the only clue that you have cracks in your shower or bathroom tile. But if you notice it soon after it becomes apparent, then repairs to the cracks will probably be simple. Efflorescence can be removed with phosphoric acid but this depends on the tile or material used, but it is important to repair the cracks and check for any other possible leaks, such as  leaking showers. Shower Repairs Plus can repair this type of crack without pulling up tile at all, and some of their services are guaranteed for over a decade
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So really, efflorescence may be a blessing if it helps you find points of moisture egress because you can often seal the leaking bathroom and prevent damage to the subfloor and other substructures. While water repellents of years ago often trapped moisture inside masonry, causing more problems than they solved, today's sealers do not do this, and they are made to withstand years of shower usage and to stand up to powerful cleaning products.

Remember that leaking showers can be unhealthy, both to your family and to the subflooring and even the floor joists if it goes on long enough. That's why it's important to stop water egress leaks as soon as possible after finding them. Wall grout and floor grout will eventually age to where they can't do their job effectively, but fortunately, modern repair compounds can make up for a multitude of small sins like moisture egress that shows up due to efflorescence. These repairs can generally be accomplished in a matter of two to four hours and they don't involve lifting the tiles or otherwise tearing up the bathroom.