Some vessel sinks have thin walls, like those of beaten metal or glass. An overflow would look awkward and be difficult to make, so they don't have one. Porcelain sinks have walls thick enough for an overflow if the designer includes it. You just have to be sure that the drain you use matches the sink, overflow or no overflow.

Kids = overflow IMO. Actually kids should = floor drain but that's not usually an option, is it?

If you don't have an overflow, you don't have to put in a stopper.

With a powder room, I'd think the sink will usually just be used for post-potty hand washing, perhaps a splash of water on the face. Nothing that would really require a sink stopper.

I say let it flow. No stopper.

with an overflow, you are more likely to get fast draining.
I can explain why in another post.

Some people install a vanity sink and find that it drains slowly.
In your case, is the drain going to be S trapped or P trapped?

thanks for your helpful responses. I'm only now thinking about the vessel sink again.
@ davidrol: I have no idea whether the drain will S or P trapped. Basically, the powder room sink will be incorporated into a console table I found, if that makes a difference. Should I request one or the other if I end up getting a sink w/o an overflow?

Sounds like having an overflow is a function of having a stopper. @mongoct, you're right, I can't think I'd have ever need for stopper in the powder room sink. I was concerned with possibly a slow drain combined with my kids blasting the water full force and playing for more than a few minutes.

I've been searching for smaller size semi-recessed vessel sinks with an overflow. Seems like the options are somewhat limited for b/c of size. Any suggestions on where to look?

S traps are code prohibited

josieindc-I was also concerned about no overflow & possibly a slow drain with kids blasting the water. The vessel sink I fell in love with is glass so no overflow. My plumbing supply store rep kept telling me I wouldn't have a problem with it & they were 100% right. Due to the lower flow rates in the newer faucets the blasting of water is much less of an issue. You can either get the stopper style drain (good point above about it being a powder room sink so you likely won't need to stop the sink up), or you can go with a grate style drain. With normal use, with the grate style drain the only thing that would cause an overflow would be a clogged drain, which would probably mean that an overflow wouldn't work anyway as the water has no where to go. The grate style sounds like the way to go and then you don't have to worry about whether or not the sink has an overflow--you can just go with what you like.

With a vessel sink, size is important due to splashing water issues. I'm not talking about kids here, just the normal splash that occurs when the water hits either the sink or your hands. The larger & deeper the sink the less splash out you have. The smaller & shallower the sink, the more splash out you will have. From what I've read, you can generally recess most vessel sinks into the counter top. Hope this helps!

mydreamhome -- thanks so much for your thoughts, which have helped to quell my fears of overflowing water! I'll be looking into deeper, recessable vessel sinks without mind to an overflow! Thanks again.