We just did this in our master bath remodel. My hubby found a porcelain tile drill bit at Lowes, and he practiced on several scrap tiles before actually drilling the hole. I sprayed the tile with a continues stream of water from a spray bottle as he drilled with the porcelain tile bit. No cracking of tiles ensued!! Good luck.

If you have acces to the wall behind the shower, you can open it up and put some blocking in there to accept a screw through the grout joint. Would eliminate the larger hole. Depends on what you think is easier. Also, can you locate the bracket so you can screw through a grout joint into a stud? Use a good sized screw (stainless if you want) and you're good to go.

Thank you for the encouragement, cordovamom!

The wall behind is a combination of an exterior wall and the top of the vaulted ceiling. I'm not certain if the area I want to install it is exterior or at the top of the interior wall. I don't think a stud finder will be able to detect the stud behind the tile (+ thinset + cement backerboard). From what I remember when the wall was apart (I'll have to look and see if I have pictures), the area where I want to install does not have a stud. There instead is a stud in the corner and one really close to the shower head. (I'd be nervous I might accidentally drill into a water line there.)

If you can install the holder over a wall stud, I'll offer an alternative idea that could allow you to drill through a grout joint and into a wall stud.

Use a fender washer and a deck screw (NOT a drywall screw) to attach the bracket to the wall.

You'd have to look at your unit to see if the fender washer and/or screw head will interfere in any way with the rest of the assembly.

But it's an idea...

If you can't locate the cup over a wall stud, then the hollow-wall anchor provided with the assembly will be your best bet.

We used the Rotozip with the Diamond bit to do ours. We had to be careful that the drill didn't slip before bitting but it worked well.

For a 5/8" hole, you're going to need a core bit. You CERTAINLY don't want someone spraying water on an electrical tool while using it! Not unless you're looking for an instant perm..... for your wake. Your best bet is to see about getting ahold of a diamond core bit, and using a CORDLESS drill, have someone hold a sopping wet sponge against the bit as you're drilling. If the sponge runs out of dripping water, stop the drill, and get another sponge full. You definitely want to keep that bit wet as you're going through. You can still get your start on a grout joint. Usually core bits have a center pilot bit that keeps the core bit steady when it starts biting into the tile. Locate that pilot bit in the grout joint, and you'll find it much easier to complete your task.

If you go the core bit route (as bill suggested), I recommend going to www.thk.hk to get them. They're from Hong Kong, but ship quickly and are dirt cheap. Get a couple just in case.

Thanks for the additional information! I had used what I believe is a core bit (instead of a standard drill bit, it was a circle edged with diamonds) for the holes drilled while not on the wall. I'm not certain what the brand was, but it didn't have the pilot bit. Instead the instructions had me place just the edge down on the tile (the bit at a 45 degree angle) and as it bit in, slowly bring it down flat against the tile. Maybe I can try out one of the professional tool shops in my city instead of the local hardware store. The sponge is a great idea. While drilling before I'd used a GFI, but had used a corded drill in order to have sufficient power. (This was something suggested in one of the many tiling books I read.) If necessary I might be able to find someone to loan me a more powerful cordless drill.

I know what you mean about cordless drills. The small ones can run out of power when grinding away at tile. I invested in a second one--originally so I could have a drill and driver handy without having to constantly change bits, but now one drills the pilot hole and the other has the core bit. Neither is very powerful. Maybe the key is to use a really good bit. I found a great selection of bits and lots of assistance about which ones would work best for me through a link on the John Bridge Forum.

Here is a link that might be useful: TYW Store

Just to follow up, thank you all for your very helpful suggestions. We finally got around to drilling the hole in the tile using a diamond-tipped core bit and a cordless drill. We even used the hand shower (that we were drilling the mount for) to spray water on the tile while the hole was being drilled. The hand shower is now securely in place and we didn't do any damage to the tile.

"You CERTAINLY don't want someone spraying water on an electrical tool while using it!"

The water goes on the core drill, not the drill motor.

It is not a real problem or hazard unless maybe you use a garden hose for the water source.

Ever seen a wet saw?

Water spraying all over the place and a 120 V (mine is actually 240 V) motor running away.