Perimeter Drainage Systems
In our city, the
greatest natural threat to the safety of our possessions
is winter rainfall and the flooding it brings. The
principal weapon to combat such problems is your
home's perimeter
drainage system (sometimes
called footing drains).
Unfortunately, most houses built locally prior to
the mid-1980's have antiquated clay or concrete
tile systems, or, in
the case of older homes, sometimes no drainage at
all.
Clay and concrete
tile systems are composed of 30cm (1') long sections
of solid 4" diameter vitreous clay or concrete
pipe laid end-to-end with small gaps between them
to allow for water entry. Over time, however, tree
and shrub roots in search of water push their way
under, between and straight through the tiles, eventually
forcing them out of line or simply breaking them.
This creates two primary problems:
· Increased
gaps allow for the intrusion of surrounding soil,
which clogs the tiles and further encourages root
growth within
· With the tiles pushed out of line, there is no longer a consistent,
downhill grade to direct water away
This problem is
compounded by the fact that concrete tile lacks the
reinforcement of structural concrete (i.e. foundation
or sidewalk) and has an inherent tendency to dissolve
over time in wet ground.
Modern drainage
systems consist of continuous PVC or ABS plastic
pipe bedded in a layer of round drain rock. A complete
drainage system includes two separate runs of pipe:
· 4" perforated
pipe (footing drain)
at the base of the foundation dedicated to picking
up the ground water which threatens to seep through
the foundation
·3" or 4" solid pipe (rainwater
lead) sitting above the perforated pipe to
take away roof water being channeled into the system by way of the gutters
and downspouts
The two-pipe system
ensures that extra rain water from the roof is not
being sent into pipes which are already working hard
to take water away from the foundation.
The two pipes
combine past the low point of the foundation into
a solid pipe traveling off the property into the
city's storm drain mains.
If the city's
storm drain mains is sitting at a higher elevation
than the low point of the perimeter drainage system
(an all too common scenario in many areas of town),
a sump pump will
need to be installed.
It is possible
(although it can sometimes create grade challenges
later on) to replace clay or concrete tile systems
one section at a time. Flexible couplings are available
to connect new plastic pipe to the old tile. Although
the final cost of replacing the entire system will
be higher, the financial burden can in this way be
spread out over several years.
Homeowners whose
drains are not working satisfactorily will often
attempt to bypass the problem by directing their
downspouts away from the house. It is important to
remember that this water has to end up somewhere.
It will either find its way back through the soil
to the foundation, create washouts in the yard, or
simply transfer the problem to your unsuspecting
neighbours.
Remember: In the
city, it is NEVER an appropriate solution to simply
direct unwanted water out to the property line. This
is how law suits happen.
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