My home is about 33 years old, when it was built there was a built-in
above ground spa. Unlike today's spas which use water jets to massage
you, this spa shoots bubbles up through a series of holes in the bench.

A couple years ago the spa began draining down to the level of the
bench and no farther. I assume this means there is a leak in the air
line somewhere underground.

There is no way I'm going to bother with fixing the leak. It would be
very $$$. What I'd like to do is turn this jacuzzi into a wading pool,
I don't care if it heats or massages.

I need to plug up these holes, and I'd like to do it without taking up
the tile. Is there any good way to shoot something (silicon glue,
concrete, ???) into the holes to waterproof them? The holes go up
through the tile grout and their diameter is about 1/8".

thanks in adv.

Is there any good way to shoot something (silicon glue,
concrete, ???) into the holes to waterproof them? The holes go up
through the tile grout and their diameter is about 1/8".

Why not just improvise a cover out of a piece of tile and thinset? Then it
can be undone later.

It doesn't need to be undone later. It needs to be permanent and I'd
like it to show as little as possible.

The air hole is in the grout between tiles... there's no covering it up
with another piece of tile.

I'm wondering if perhaps I could find something like a plastic cylinder
of the appropriate diameter to insert in the hole then cover with grout
or concrete? The surface tension of the wet material (glue or concrete
or whatever), and the tight space, makes it hard to apply the filler
material.