Clark Grave Vaults' dome-shaped
design allows air pressure inside the vault to keep water below
casket level just as the air in a submerged inverted glass keeps
the water from coming up inside.
The box-shaped design causes the casket to soak in water. Liners
are often made of porous materials such as concrete, which allows
water to pass through, soaking its contents and compromising its
weight-bearing strength over time.
A casket will not withstand the weight of the earth's load or heavy
cemetery digging equipment driving over the grave. Without the protection
of a grave vault, the casket and its contents may be crushed. A
depression may appear above ground.