Gardens: use of Rainwater. Garden Swimming Pools
In the design of new buildings it is desirable to include means for collecting and storing rainwater. Rainwater systems can also be installed in existing houses or gardens. The storage volume should be generous because the greater the volume, the more the potential economies. The average storage required for garden watering (given 40-60 l/m2 as a typical annual usage) for a single family house is about 50001 (it depends on the area of garden, annual rainfall, roof area and run-off value).
To calculate domestic water needs, use the following figures for average water consumption per person per day: 151 drinking/cooking, 101 washing, 401 bathing/ showering (total: 651 potable water); 181 clothes washing, 41 cleaning, 451 WC flushing (181 with economy flush), 81 sundries (total: 751 rainwater or 481 with economy flushing).
Example. Annual rainfall 800mm = 800l/m2
Pitched roof run-off value f = 0.75
Net roof area = 120 m2
Rainwater production = net roof area (m2) x annual rainfall (l/m2) x run-off value (f)
800 x 120 x 0.75 = 72000 l/year
Number of persons = 4 Usage per day = 451 per person (WC with economy flush)
Garden area = 200m2
Annual garden watering = 50l/m2 Rainwater requirement = persons \ usage per day (I) x 365
days) + (garden area (m2) x usage per year (l/m2))
(4 x 45 x 365) + (200 x 50)
= 75700 l/year
Factor g = (1 - [rainwater production
rainwater requirement]) x 100%
(1 - [72000/75700]) x 100 - 4.9% (this is less than 20% so use g = 0.05) Storage requirement =
rainwater production (I) x g
72[t]000 x 0.05 = 36001
Recommendation: 4500I rainwater storage tank.
Explanations. Net area: the plan area of the roof connected to the gutters (equivalent to the plan area of the house).
Annual rainfall: mean annual rainfall (e.g. typical values are 740-900 mm = 740-900l/m2) as read from appropriate rainfall maps or information from a local weather station.
Run-off value (f): f = 0.75 for pitched and flat roofs.
Factor g: when the difference between rainwater production and rainwater requirement is less than 20%, use g = 0.05.
g = 0.03 when the difference between rainwater production and rainwater requirement is more than 20%.
g = 0.20-0.40 when the water is used mainly for garden watering and when there are large seasonal rainfall variations.
Garden Swimming Pools. The ideal position for a garden pool is sheltered from the wind and visible from the kitchen and living room (to allow supervision of children). There should be no deciduous trees or shrubs immediately next to the pool and a surrounding walkway ought to be provided to prevent grass etc. from falling into the water.
Realistically, the pool should no less than 2.25m wide and the length worked out on the basis of a swimming stroke length of approximately 1.50 m plus body length (e.g. four swimming strokes equates to 8m). The standard water depth is usually based on the average height to the chin of an adult. The difference between the overall pool depth and the water depth depends on the type of water extraction system (9) – (11).
For reasons of cost and the water circulation system (see below), the shape of the pool should be kept as simple as possible.
The standard type of pool design uses a sealed surface on a supporting structure made of masonry - (8), concrete, steel (particularly for above ground pools) or dug out of the earth - (5). Polyester pools (which are rarely made on site, being mostly made up from prefabricated parts) are generally not self-supporting so lean concrete backfill necessary - (6). Cast or sprayed concrete pools - (7) must be watertight. The surface is usually ceramic tiles or glass mosaic, although they are sometimes painted (chlorine rubber, cement paints).
The water needs to be kept clean and this is normally done by water circulation systems and filters. The process is improved with a good surface cleaning system using a skimmer - (8) or channel – (10) + (11). Adding a regulated countercurrent plant or through-flow heater can extend the swimming season considerably without prohibitive costs.
Other factors to consider are child-proofing measures and frost protection.
Date added: 2023-01-05; views: 185;