I think a lot of undermounts are being 'glued' in place with silicone sealant, which actually isnt' very strong.

There are supposed to be clips, drilled into the underside of the stone to hold up the sink. Without those, failure isn't just likely, it's darn near inevitable.

Why so few are supported from below is also a mystery to me...

They aren't meant to hold a great deal of weight but not using the clips/hardware per mfgr's install voids the sinks warranties.

The installers I use adhere undermounts with a two-part epoxy. I've had no complaints. (Though I haven't had any of my kids jump in them to test the strength.) What I haven't thought of, I admit, is how you remove the sink when the time comes for a change.

It's hard to know if it's installed improperly when the mount was broken by improper use. I'm not sure even the clips would withstand a falling (even small) child. I hope the girl is okay, and her parents put in a rule of no standing on the counter. Oh, and that the sink mount can be repaired without much expense.

"The installers I use adhere undermounts with a two-part epoxy. I've had no complaints. (Though I haven't had any of my kids jump in them to test the strength.) What I haven't thought of, I admit, is how you remove the sink when the time comes for a change."

...or when you have to remove the faucet to fix or replace it. With some faucet and sink combinations it is really hard to remove the faucet with the sink installed.

Thanks for the replies, good information. I know there are thousands of undermount sinks installed these days, but these replies make me wonder if I want to go that direction in our future home! Any one had to worry about replacing the sink or faucets and run into problems?

Our main kitchen sink did this at Thanksgiving, no less. It wasn't fun trying to wash dishes in a prep sink, let me tell you! My DH and I are DIY idiots, but fortunately out friends that were here are not and he was able to prop the sink up with 2 x 4's to prevent any of the pipes or the dishwasher drain from being affected. Called our builder and he got the granite guys over here the next day. They have only used one of the two ypes of "glue they are supposed to use on the sink. We had them check every sink and they found one other that was the same way. They agreed to extend their warranty and additional 6 months because in their words, "we really screwed this up". Yes, you did. We didn't have to replace anything and had no damage to the faucets or dishwasher either. Just inconvenience.

We have a Blanco undermount kitchen sink installed in a Zodiaq quartz countertop. It was first installed in December of 2006. In December of 2007 - one day before the installation warranty expired - the sink failed suddenly and violently crushing plumbing and flooding the kitchen with sink water.

We were told that the first guys shouldn't have used silicone and didn't install it properly, etc... and that it should be 'blocked' in place by using an epoxy to attach blocks over the underside lip of the sink. This sounded great.

Two weeks before Thanksgiving this year (2007) this new installation also failed. It wasn't nearly as dramatic as ONE of the blocks installed held the sink teetering in place although it had totally broken away from the counter.

The Zodiaq installers just came out yesterday to reinstall our sink. The previous installers no longer install Zodiaq counters or undermount sinks. Hmm. Wonder why? So now we get to see if THIS one stays in place.

The clips sound like a GREAT idea - but none of the folks we talked to had ever heard of such a thing apparently.

Here is a link that might be useful: Pictures/sink story here

All undermount sinks and lavatories should be mechanically attached. Installing one with some kind of glue would most likely be a violation of any specification that required the contractor to follow the manufacturer's installation instructions.

Whatever happened to: "If you fool around, you're going to get hurt".

A four year old can generate a lot more force than you might think. Having her foot slip and go into the sink is more force than her weight alone. I'm not surprised it failed and wouldn't expect it to hold under those conditions. Thankfully she's ok. And hopefully your niece learned a lesson about where children do and do not belong.

All undermount sinks and lavatories should be mechanically attached

I just double checked those in my own home: the kitchen sinks are mechanically mounted and epoxied; the bathroom ones are only epoxied. When the time comes, I imagine a sledge hammer would be useful in removing them.

Mine are all clipped: do I get a prize? I actually played the dummy and asked different stone yards how they attach undermounts, thinking it would be one way of seperating the wheat from the chaff. All of them I talked to explained about clips, so it wasn't helpful, though it was reassuring.