"Very small joints" generally refer to 1/8" or less. What kind of tile did you use? If the sanded is holding well and looks OK, I see no reason to re-do it. I have used sanded in a small joint before and it "will" work...but sometimes not as well as unsanded. Got a pic?

The tiles are the standard plain ceramic bathroom wall tile, which I think are about 4 inches square. They were already there in the bathroom, but the grout was chipping and falling out so we wanted to replace it.

The joints are definitely less than 1/8" inch. In some cases, the tiles seem extremely close together. I'm worried that around the tub, the sanded grout isn't going to give as good a seal because of these small joints.

This is what I get for listening to the Home Depot guy!

Yep, they really will do better with unsanded. If you're gonna remove it, sooner is better than later. You might try running a utility knife down the joints to remove it. Sometimes this pulls the grout out quite well. Angle the blade a bit to one side and then go back at the opposite angle. You probably don't have to get it ALL out, but go for at least 75%.

Well...

Disclaimer: interested amatuer, no training in tile. But--

Grout doesn't 'seal' anything. It takes up space so nasty stuff can be wiped off, rather than having to dig it out of the cracks.

Sanded grout is stronger, more abrasion resistant than unsanded. The big reason it isn't used on narrow joints is that the matrix of the sand itself [the way it clumps together, the grains basicly interlocking like bricks] makes it very difficult to work all the way to the bottom of a narrow grout gap.

Unsanded does have [realitively] more cement, so its 'glue-ier' than sanded, and may cling to the sides of the tile a little better. Makes a difference on a narrow gapped floor, but I don't *think* it will on a tub surround.

So if the install is all done, and you really, really worked at mashing that grout deep into the gaps, I honestly think your OK: you made it harder on yourself, but you didn't do anything 'wrong' that will affect the way things work.

But if you essentially just wiped the grout accross the surface instead of filling the gaps from the bottom up, then there is a chance that the air gaps below will cause the grout to crumble and fail.

What will you do if that happens? Exactly what you are contemplating now: digging it out and replacing it. It will be a little tougher after the cement in the grout fully cures.

So you have to ask yourself: are you comfortable that the grout fully fills the gaps, or do you think it's likely that there are some pretty big air pockets down there?

I stand ready to be corrected by any of our tile pros...

You're right, as far as that goes. My concern is that, if he didn't really "force" the grout into the joints....that's a recipe for failure, and most "newbies" don't really work the grout in as well as it should be done. I'd really like to see a picture of the job before I comment more.

And you WON'T work sanded grout into 1/16" grout joints. It just can't be done without an inordinate amount of effort. I agree with Lazarus. That needs to be carved out ASAP.