Percival P. Cassidy wrote:
For a while after we moved into this house the shower stall looked fine,
but then the grout lines -- especially those between the edge of the
floor and the bottom of the walls -- started looking dirtier and dirtier.

The usual shower cleaning products did not do much, nor did undiluted
bleach straight from the bottle.

We thought of redoing the shower with plastic or fiberglass panels, but
it's significantly smaller than any standard off-the-shelf units. No
doubt we could get a custom liner made, but probably costing more than
we would be willing to spend.

I've just started attacking the grout with a grout saw, with the
intention of regrouting those joints, but it appears that the previous
owner used silicone caulking compound over the existing grout along
those edges. This complicates cleaning out the crevices. And even where
I've managed to clean out the old grout and caulking compound,
everything is still black, and even straight bleach seems to have no
effect.

Any suggestions about the best way to deal with this?
It's not too much work if you use a Fein Multimaster with their carbide
tile blades. To remove the grout is a leisurely day, and to regrout is
perhaps 4 hours. Once the grout is out I'd wash the surfaces and grout
streets down with a good mildewcide like those sold by Zinssner before
regrouting.

Boden