Graven Water wrote:

I need to remove some paint from a concrete block wall, before
waterproofing it.

Is this wall below grade (ie - a basement wall) ?

I have a drill that uses bits with 1/4" hex shank.
So far I've tried a 4" brass wire wheel and a small brass wire cup.
The wire cup doesn't work at all. The wire wheel gets off a lot of
the paint, but not all of it. The problem is the roughness of the
concrete block surface. The wire wheel does fine at removing the
paint from the mortar between blocks.

Depending on how big this wall is, using a drill with a wire brush can
be really labor intensive.

And you can mess up the grouting beteen the blocks if you're not
careful.

I can get the paint off fine by hand with a tiny wire brush I have,
if I really bear down. But I have about 100 sq feet of wall to do,
and that would be way too much work.

I'm sure sandblasting would get the paint off, but I've never
sandblasted anything and I don't know anything about it. I don't
know if you can rent a small sandblaster. There's a ceramic tile
floor, a wood staircase and a painted closet near that area that
would have to be protected. Sandblasting would make a big mess.

Ok, so what I'm getting now is that you're working on the *INSIDE* or
interior face of this block wall.

I've never had to deal with a water problem for a block wall, but it
would be my guess that you can't fix such water problems from the
inside. You have to make the wall waterproof from the outside. And I'm
thinking this is a basement wall.

Is there some kind of wire brush that would work better than the
ones I've tried?

I think you're wasting your time.

You don't waterproof the interior side of walls.