Keurig b40 coffee maker leaks water from underneath the water pitcher. what is wrong with it? It has ruined the grout around my kitchen tiles from all the water leakage.

Seals could need replacing. If your fairly handy you can replace them.

Here are the seals;
http://iwantsweetdeals.com/Keurig-Replacement-Water-reservoir-Seals--P1286283.aspx

You can purchase a replacement reservoir here;
http://iwantsweetdeals.com/Keurig-B40-B60-Water-Reservoir-Tank--P1207341.aspx

I had this problem as well. We took mine apart after getting nowhere with Keurig support. The problem that I ended up having is VERY easy to fix. Remove the TOP of the keurig - remove the handle with 2 screws on each side, then there are a few screws up inside the actuating lid that can be removed so that the top black plastic actuating lid can be removed. The problem that I had is that the plastic clip that holds the tub from the hot water reservoir had come loose and now water was being pumped out of the hot water reservoir into the inside of the keurig and not into the k-cup. Simply place a zip tie over the tubing to attach it to the hot water reservoir, replace the poorly functioning clip (otherwise the lid wont actuate properly and will make clicking noises) and replace the lid. I have had no problems since. This was not a "seal" problem in my case, just a crappy clip holding the tubing onto the hot water reservoir. Check this out first before doing anything else (like taking the bottom off). Thanks to my brother and father-in-law for discovering this fix - otherwise I was about ready to put the B40 in the trash.