Shower Floor Grout Turning White

It is due to soluble salts rising to the surface of a cement based product.
Shower floor grout turning white. This is not efflorescence. In january 2017 i noticed a dark jagged line about a 1 4 inch wide on the pebble shower floor from the middle of the shower door opening at the top of the floor pan to the drain. The problem you have is called efflorescence which occurs when any concrete product is over washed before it is cured. The minerals in the water crystalise which results in white residue appearing on the surface of tiles.
Topical sealers acrylic sealers which coat the grout joint and are not vapor permeable may turn white from reactions between the acrylic and moisture. Some caution must be observed in selecting the sealer. So no you do not have to remove the grout. Grout turning white can be caused by efflorescence which is the calcium from the water and the underlying concrete or mortar migrating up through the porous cementitious grout.
Known as efflorescence white stains appearing on the surface of tiles is caused by water penetration underneath stone or tiles. This is a natural phenomenon called efflorescence. The most common reason is moisture from the ground below the slab but grout may also turn white from the rain in outdoor installations or in rare cases from water used to clean the floor. When they dry out on the surface the remaining salts appear white and powdery.
Another possibility is that grout containing polymer was used and exposed to too much water before the polymers had a chance to combine. I am assuming that the white jagged line represents a crack in the grout and the white is efflorescence. Excessive efflorescence is considered a symptom of an excessive moisture problem. My shower floor is the same type as this person s i don t have that odd white discoloration though and no cracked grout along edges.
Under certain circumstances a white powder can form on grout especially on floor tiles. They have an efflorescence remover on the market but they only work so well with grout. A week later the line turned white. Rather this is similar to the whitish haze seen with floor wax when it is applied to a damp surface.
Answer when there is a white haze on a shower floor it is normally either efflorescence precipitation or you have trapped moisture in the tile assembly by applying a non breathable sealer over the floor. Make sure that you get a good sealer onto that grout before you get after it again with water.