Why make caskets water tight?

From:  "redddogg"

they warrant the concrete boxes that a casket goes in to be water tight. Has anyone ever been exhumed to check on the warranty? or has it ever been proven that it works? Finally, Why do the warranty them in the first place?

TB was the first to give us his thoughts: 

Certain locales require waterproof caskets to prevent pollution of the water table. A waterproof casket is also needed when transporting cadavers that are in advanced stages of decay. A warranty tells people that the casket company stand by their product. I will take a casket that has a warranty over one that does not when they both say they are waterproof.

Dave Varet gave us this insight on the question at hand: 

it is not the water getting into the caskets, but whatever organisms might have contaminated a body (say the plague back in the good old days when the grim reaper worked hard for his money). This is a little bassackwards for it is good for a body to decompose (hence the jewish tradition of loose caskets) but hey, no one ever claimed Christianity to have logical traditions.

KJ gave us this to think about: 

They probably make caskets watertight and warranted so as not to piss off the vampires. I don't know about you, but if I were in a nice sound sleep and my beds roof leaked and no one would fix it, and also I had super powers, I'd come after ya, but at night cause I hear vamps are like that.

Swammi gave us this interesting piece of information: 

The concrete "boxes" are actually called "burial vaults" and some cemeteries require them to be watertight if they are within a certain radius of a body of water, river etc. It is more design to keep things from LEAVING the vault, than it is from keeping water from getting in. Over time erosion of the ground near streams etc. might allow things that belong inside the casket/vault to enter the water system.

salvia tried helping out with this: 

the answer on caskets I think is about an accident before the body has got into the casket or before it goes into the ground also the less moisture there is the slower the body will rot and decay

Maus gave us this information: 

Caskets are designed to be water tight for areas in which the geography is at or below sea level, meaning a high water table and the potential for groundwater contamination.

Paul did a report and sent us this: 

To understand the reason why the concrete casing around a casket is water-proof, you must understand a little about how modern burial practices got started.
Early man had discovered that rotting human bodies bred disease. So man started to bury the bodies of the dead. Unfortunately, the graves were often shallow and this attracted all kinds of savaging animals to the burial site. Man then started to cremate the dead. This practice continued until the Christians came along and prohibited the practice, after all, how is the body expected to rise into heaven if there is no body?
To solve the problem of attracting scavengers to the graveyards, the bodies were placed in wooden boxes. This protected the body from being eaten by animals. However, what wound up happening is that the wooden casket and body would both decompose. When it would rain, the rain water would filter through the ground and the decomposing bodies and contaminate the ground water, which spread disease. To solve this problem, the casket was placed in a waterproof container, the sarcophagus, to keep from contaminating the ground water.