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How To Make Low Cost Cisterns? The Fence Cistern!

How to make low cost cisterns? The fence cistern!

How to make low cost cisterns? The fence cistern!: cisterns

For the success of rainwater harvesting for home use, it is essential to have technologies that combine simplicity of construction, high resistance and low cost.

Three factors that seem difficult to gather under one roof.

The fence cistern seems to meet these three requirements. It fits in ferro-cement technology, which guarantees high strength.

In addition, the construction has a low input of materials and is very simple: on a concrete base is placed a wiring screen, cylindrical, already in the size of the future tank.

To allow the application of mortar, the screen is wrapped with sacaria of the type used for onion.

The application of four thin layers of mortar confers the required strength to the wall.

The ceiling consists of similarly manufactured segments.

The cistern presented here has a storage capacity of 16 m³, but easily its volume can be enlarged or reduced by simply adding or subtracting a few decimeters of screen.

Why and how to do it

For human use, the collection of rainwater requires a safe and closed reservoir, so that there is no leakage or evaporation.

Over the years, after attempts and experiments with various materials such as bricks, stones, synthetic materials, the most resistant cylindrical shells of cement mortar have been shown.
In these, the ferrocement technology stands out for its great resistance and reduced use of materials.

Traditional ferro-cement technology employs several fine wire meshes tied together in a steel rod structure that supports the mortar's own weight.
The construction of this structure is time consuming and always employs more steel than is necessary for the safety of the reservoir.

The screen and wire tank technology represents a simplification of traditional technology, while maintaining the basic ferro-cement principle that guarantees resistance and safety against leakage.
No vertical steel bars are used, but a flexible, removable steel sheet form around which the screen is wound and around the screen, the galvanized wire.

The support of the wall, while the fresh mortar, is assumed by the mold, which is removed after the application of the two outer layers.

The challenge for the new technology was the elimination of the mold, without giving up the simplicity and the security that the ferro-cement offers and of the whole wall, without seams or composition by singular elements.

A product of the steel industry, widely used to separate open-air spaces such as homes, parking lots, etc., was offered as an ideal:

wire mesh, a two-meter-high mesh 15 cm x 5 cm mesh, galvanized wire 3 mm in diameter, with a breaking strength of 65/70 kgf / mm² - slightly higher than wire 3.4 mm used in the construction of cistern with 50 kgf / mm², with the same volume of storage.

The screen is supplied in rolls 25 meters long.

The application of the mortar in four layers imitates the principle of composite materials, such as veneer plywood or armored glass.

The construction

The construction follows the basic procedures of tank-shaped construction: at the construction site the layer containing organic matter - usually around 20 cm - is removed and compacts the soil.

Next, two layers of seven centimeters each are placed, one of rolled pebbles, one of coarse sand (washed), both compacted, which serve as a foundation.

Within the next layer of the counter-floor, the fence screen is placed and secured, Photo 1.

Care should be taken to securely attach the portion of the concrete placed on the outside of the screen cylinder with the inner part, Photo 2.

The screen cylinder needs to be leveled with hose level.

How to make low cost cisterns? The fence cistern!: cost

The next step, placing the first mortar layer, to stabilize the screen and allow the application of the structural layers and seals, found a surprising solution.

The challenge was to find some way that would hold the first layer of mortar close to the steel screen.

In the original ferro-cement technology several layers of fine wire mesh are applied and in the application of the dough, a second person secured on the other side a piece of fine plywood, or similar, so the dough does not fall into the void. But this would not be the proposal.

He had to find a solution that would secure the mortar easily, without making the building more expensive.
It could not be something of organic material, because by the thin layer of mortar small amounts of moisture penetrate and decompose the organic material, which causes gushing and destruction of the concrete.

As a solution the sacaria used for onion was offered. It has a capacity of 20 kg, is made of polypropylene yarn and mesh fabric type English swivel.
The mesh is very thin and does not let the mortar fall to the other side at the time of application and is strong enough to be tight and tight around the fence.
It takes 25 bags of onion, previously well washed that will be fixed with synthetic cord, one lap every five centimeters, Photo 3.

With a flexible nylon spatula the first layer of mortar is applied, to stabilize the wire mesh, Photo 4.

The sacaria is not placed as a structural element, but rather as a simple support to support the application of the first layer of mass.

How to make low cost cisterns? The fence cistern!: make

In order to avoid the elastic movement of the screen, caused by the application of the mass, the screen cylinder must be fixed in its position with wire, stretched out, and wooden struts from the inside.

On the following day the second outer layer is applied and on the subsequent days two inner layers, all of them with a thickness of approximately one centimeter.

The composition of the mortar is one part of cement to two parts of coarse sand (washed, without clay) and one of medium sand, of the type used for plastering of walls.

Two observations must be made:

- the application of the layers must be carried out at once without interruption;

- after each step the cistern should be covered by a tarpaulin and the wall be wet copiously before the next step. This will allow cure of the mortar, and prevent premature drying.

The roof

The ceiling is formed solely of 17 segments of plates, with a fence screen frame and a thickness of one inch.

Photo 6 shows the screen segments cut off, and Photo 5 shows the application of the second layer of mortar in the still fresh bottom layer.

How to make low cost cisterns? The fence cistern!: cistern

How to make low cost cisterns? The fence cistern!: cisterns

How to make low cost cisterns? The fence cistern!: make

It is important to remember that the cover plates must be manufactured as a first step, before starting the construction of the tank, since the concrete needs time to cure and thus avoid breaking the plates at the time of placement.

The plates are supported in the center of the cistern in an anchor, placed in their positions in the form of a sloping roof.

How to make low cost cisterns? The fence cistern!: fence

Finishing

After grouting and fixing the plates between themselves and the wall of the cistern with mortar, photo 8, follows the placement of the floor, in the thickness of three centimeters, all with a trace of one part of cement to three of coarse sand.

The results obtained from the construction of the wiring screen cisterns show that this technology combines safety and simplicity of construction.

The cost turned out to be the lowest of all today's most widespread tanker models.

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