We hope to be able to store enough rain water to use it for all non-potable water in the house and have excess for watering the garden.
The rainwater collection system will drain all of the roofs, process the water and fill the tank. The main house has a collection area of 355 m2 and the garage is 75 m2, this give a total of 430 m2. This give a rate of 430l of water for each mm of rain falling. Excess water will go to a soak-away for disposal.
Part of the design is too reduce the level of contaminates in the stored water by discarding the first few hundred liters of water in any period, thus most of the dust and pollution which will collect on the roof between rainfalls will not reach the tank. Because the roofing is wood a some water will be lost to absorption.
Gutters will be formed from Timber as a integral part of the facia. The inside of the trough will be have a EPDM liner which will also act as the eaves tray. Discharge will be through standard 68mm downpipes which will be inside the walls. All joints will be glued.
Downpipe will feed a 110mm pipe buried shallowly around perimiter of the house, this will feed a filter unit.
The filter unit has two stages. Water enters the unit at the front onto a pair of baffle plates draining into a 200l sump. This sump will have a simple sand filter at the bottom to collect silt and discharge through a controlled exit to the soak-away. The drain time of the sump will be set to approx 1 week, this means the first 200l of water from the roof will be discarded if it has not rained in the last week. Hopefully this will allow the roof to cleaned by the first rain in any week.
When the sump is full (i.e. more than 0.5mm rain has fallen) the water level will rise over the dam into the main filter section. This will have a layer of sand over gravel to remove most particulates from the water which will drain into the storage tank through a 50mm pipe.
If the rain fall is heavy then the filter will fill up until the weir is reached. The water will then start filling the swimming lane/pond. This will give a surge storage of at least 6000l (and refill any water lost by evaporation). In a deluge situation even this may not be enough so there is an overflow at the top back into 110mm pipe straight to the soak-away which itself has a storage capacity of another 5400l.
the storage tank will be made on site from Wavin Aquacell Core modules wrapped in a sheet of EPDM pond liner.
The soak away will be made from the same Aquacell modules as the tank but without the mebrane!
Drive way & paths
The main drive will drain into the main soak-away via a seperate connection to the collection system. All of the other paths will drain off the edges in the surrounding soil.