Quote:
Originally Posted by Piwoslaw
One more question: what happens when the cistern is full? Where does the overflowing rainwater go? Sewage, or underground?
Sorry about the dumb questions, but I'd like to store some rainwater underground and would like to know which technical problems I'll need to solve along the way. |
The cistern is the small container inside the pump/control unit, which mixes mains water into the rain water pipes in case the rain water tank is empty. The cistern is used to ensure that there is no physical possibility for rain water to be pumped back into the mains water.
The rain water tank is prepared for overflow. This can either go to the sewer, or you can install an infiltration cavity in the ground. Depending on how well the soil absorbs water (this can easily be tested), you need a certain size to ensure you can process all the excess water.
I am using the infiltration cavity solution. It is a mesh of environmentally friendly plastic units, combined to a larger box which is then encapsulated in a fibertex membrane (to keep dirt out). I have specifically made mine so that I - besides the sand catching unit - have a vertical 110mm tube extending from the infiltration unit bottom, to the surface.
This enables me to see the level of water inside, and if it tends to build up, I will consider installing a farm-type mechanical pump, for irrigation purposes. The water in the infiltration box is sufficiently clean to use for this purpose.
By disconnecting rain water entirely from the sewer, I get a cash refund, which is quite substantial (about 3000 USD), as it helps save the sewers from overflowing when it rains a lot in a shorter time. If enough people did this, we would not have those expensive overflows, flooding peoples basements and overflowing the sewage cleaning plants thus polluting lakes and streams.