Building a home on a lot
means consuming open ground. Open ground is essential for absorbing water, so
less ground means less chance to absorb water from rain and snow. This means
that the water that accumulates needs to be dealt with in another way. In most
cases this water is funnelled with the use of gutters, downspouts and sloped
driveway slabs to a storm water system run by the town or city. This causes a burden on the town or city. The
idea of requiring each new home to deal with its own accumulating site water rather
than relying on the town or city is a growing requirement for many
jurisdictions.
While we have provided on site dry wells
(gravel pits buried in the ground to capture the water and allow it to be
dispersed back into the town’s storm water system at a slower rate), we have
gone one step further and provided a water storage tank buried below ground.
The water that we are able to gather and store will be used for watering our
garden.
The tank we used is from Premier Plastics and is a 4000 litre tank buried at the side of the house. In terms of
how much water we can expect to accumulate and use, Outland Design did the
following analysis:
- We have the potential of collecting 5800 litres of water from rain runoff from the roof and walk way areas (based on environmental information and roof area).
- With a garden area of 5 m2 which would require watering at 25mm per week, the volume of water required would be 0.125 cubic meters or 125 litres per week.
- With a 4000 litre cistern we will be able to provide water for approximately 32 weeks or 8 months of the year.
The benefit of our sloping site also
allows us to use gravity to make all of this work. No pumps required. Water
drains from the roof and site down into the tank in the ground. The garden area
is below the tank on the lower tier of the lot which allows the water in the
tank to flow down to the garden area. There are some extra costs to this system,
but the benefits of having a water supply that is not tied to drought
restrictions imposed by the City, and making use of the water gathered rather
than paying for it, have their benefits.
