Assuming
its in reasonable condition, most modern tents are very
well sealed against the elements. Where they have the
biggest problem is in water coming up through the floor.
Its hard to prevent small pinholes from occurring in tent
floors because they are almost always pitched on top of
things that might cause punctures like sharp rocks or
small sticks. Add to that the weight of people inside the
tent forcing the fabric down against the sharp objects
and you've got a situation where small leaks are bound to
occur.
Carrying
a ground sheet to pitch under the tent can extend the
water proof life of the floor. If you use a ground sheet,
make sure that it doesn't extend beyond the tent floor.
It will act as a funnel and direct water under the tent
if the material goes beyond the floor.
An
additional protection against water coming inside is to
carry a sheet of plastic big enough to make a "bathtub"
inside the tent. The material used as a vapor barrier
behind drywall in a house is perfect for this task. Put a
piece of it inside the tent when its pitched on your lawn
at home and trim the excess a little higher than the
width of your hand. While you're at it, cut an extra
bathtub and pack that for longer trips.
Choosing
the tent site is very important if there's any chance of
rain. Very important to make sure the tent won't be in a
trough or funnel if there's a downpour. Check to make
sure the site doesn't feel damper than the surrounding
areas. Moss is a sign of wetness and should be avoided.
Signs of water erosion on a path near the tent might
indicate a natural gathering point for water in
downpours.
