Find the bag or bucket first

Ask for the product name, batch information, installation date and any leftover material. Cement grout mixed with water, epoxy grout and ready-to-use grout do not share one curing process. Instructions from a different product can make the investigation less useful rather than more technical.

Record when the room was heated, when the surface was washed and when the shower was first used. Photograph the affected areas in dry conditions. Avoid scratching out large patches while the installer and manufacturer are still assessing the problem; that can remove evidence and damage tile edges.

Dust on top or a weak joint?

  • A light film that wipes away

    May be installation residue; assess the joint after approved cleaning.

  • Repeated shedding from the joint

    Check mixing, cleaning and curing against the exact product.

  • Voids or crumbling sections

    Ask about removal depth and replacement, not simply sealing.

  • White crystals returning

    Investigate mineral deposits and moisture as a separate issue.

Too much water is one possibility, not the only diagnosis

The Polyblend Plus data sheet warns against adding water to stiffening grout and calls for minimal cleanup water. It also says curing depends on temperature and humidity. Those are useful checks for that cementitious grout, not proof of what happened on every bathroom floor. CUSTOM: Polyblend Plus sanded grout technical data.

Other possibilities include poor proportioning, material beyond its usable condition, cleaning at the wrong stage or early water exposure. Have the installer compare actual practice with the recorded instructions. “It needs another coat of sealer” does not answer why the joint is coming apart.

Agree on a repair that reaches sound material

A manufacturer or tile professional should decide whether the issue is superficial or whether grout needs removal and replacement. A thin smear over loose material usually leaves the weak layer underneath. Removal depth and tooling matter, especially in a shower where aggressive cutting can reach the waterproofing.

Keep the area out of service for the specified repair cure, then inspect before sealing or normal use. If the joint is firm but a pale film covers the tile, start with white haze on new tile. If it is sound and simply porous, the sealer guide answers a different question.