Why Choose a Flexible Water Tank to Collect Rainwater?
– Principle of the flexible water tank
– Why choose a flexible cistern to collect rainwater?
– Installation of a flexible cistern
– Price of a flexible water cistern
Why Choose a Flexible Water Tank to Collect Rainwater? The self-supporting flexible cistern is one solution for rainwater harvesting, along with the concrete tank and the polyethylene tank. It is also known as a flexible tank or a water pocket.
Principle of the flexible water tank
The flexible water tank is made of high resistance polyester, coated with PVC. The materials must comply with sanitary standards so as not to alter the water they contain. They have a lifespan of about 15 years.
The cistern is shaped like a cushion allowing it to be self-supporting and ensures its solidity. The corners must be reinforced.
Most cisterns are used to store rainwater, but they can also be used as a fire reserve or a drinking water supply for humanitarian missions.
Why choose a flexible cistern for rainwater harvesting?
A healthy and easy to install solution…
The advantages of a flexible water cistern are numerous:
– The cistern is closed, so there is no evaporation. All recovered water is conserved.
– The fabric remains attached to the liquid. The absence of air in the flexible tank prevents oxidation, contamination by micro-organisms or by pollution, and the development of mosquitoes.
Since the tank is opaque and treated against UV rays, there is no photosynthesis and no algae.
– The flexible tank is easy to transport and set up. The flexible tank can be quickly emptied, cleaned, stored, or moved. The materials used in the tank are all recyclable.
– The installation of a rainwater harvesting system with a flexible tank does not require a building permit.
– Most flexible cisterns are square or rectangular. Some are narrow for a longitudinal arrangement.
… but must be placed in a discreet location
Aesthetics and size are the main limitations of a flexible tank:
– A flexible tank takes up a lot of space on the ground: for 4 m3 (4,000 liters), count on a surface of 3 m on each side, for a height of 0.65 m.
– Most flexible tanks have a green, grey, or yellow plastic exterior. It is essential to be able to conceal them while remaining close to the gutters…
Installation of the flexible tank
A single person can easily install a flexible tank.
Where to place it
You can place a flexible water tank both indoors and outdoors. It is placed on the ground. For aesthetic reasons, locations that conceal the tank are preferred:
– crawl space ;
– under a terrace;
– behind a building or a hedge.
The cistern should be located near the central gutter of the building, where it will be fed.
How to install it
The flexible water tank should be installed on perfectly flat, stable, and clean ground, ideally on a bed of sand covered with a geotextile film or a PVC floor mat.
The collector will be placed on the gutter at the maximum height of the entire tank.
There are rainwater harvesting kits, which contain :
– a gutter collector,
– the connection pipes,
– a suction pump to draw water from the cistern.
These kits are easily connected to the cistern: the collector on the valve located above the cistern, in the middle, and the pump on a valve located on the side of the cistern.
For sanitary use (WC, washing machine), you must add a filtering device.
Price of a flexible water tank
The price of a flexible water tank depends on its size, and its size depends on the capacity you need, which depends on
– the rainfall in your area;
– your roof area;
– your water needs (size of the garden to be watered, sanitary use or not, filling of a swimming pool);
– the space you have to install your cistern.
A flexible cistern costs $150 to $3,000 depending on its capacity (from 500 to 100,000 liters). A 5,000-liter bladder (a little less than 3 × 3 m on the ground and 1 m high when full) costs about $500.
You must add the collector’s cost (about $100 for a kit) and the pump (from $250).