Grout not waterproof?

[Woods94]

HI guys - recently installed a new shower with 2 tiled walls over tanked hardiebacker stud walls.

Getting a bit of trouble with water egress to both corners, I've reapplied the sealant around the tray and fairly confident it's not that. I've noticed the grout lines between the tiles go very dark when they're wet and I'm wondering whether it's allowing water through, down the waterproofing behind the tiles and out along the top of the tray.

I used Mapei flexible wall & floor grout (Not the ultra stuff) says it's fine for showers but I spoke to the mapei technical people and they said that it sounds like water is getting through the grout lines and they need sealing - does anyone have any similar experiences and can recommend a good sealer? I'm wondering whether raking it out and using epoxy is just easier in the long run

Cheers!

 

[Mark DM]

When you say egress, is water coming out between tray and tiles? Have you sealed the internal wall corners top to bottom. Often a crack can appear here and draw water through via capillary action. If your grout stated waterproof rather than water resistant then a sealer shouldn't be needed. Strange comment from the manufacturer... was it a fresh bag and not been stored for an extended period.