A casing for a water well is a special chamber for the mouth of a hydraulic structure at a level below the earth's surface. It is installed above the water intake shaft in order to achieve the most comfortable access, and for the subsequent installation of autonomous water supply equipment.
Functions and Purpose
During the winter cold season, well operation is complicated. During frosts, water raised from a depth freezes and spoils or ruptures pumping equipment. For normal operation of the well, the owner needs to make sure that its head is warm. Using a caisson, you can create such conditions.
The device of a standard caisson for a well is straightforward. This is a tank that does not allow water drains. It is placed in the ground and mounted on the casing. Thermal insulation will protect the well shaft from the cold.
Caisson is used to install pressure equipment. In it, it is closed not only from subsurface waters, but also from insects and rodents.
Inside the structure, you can put everything you need to use the device’s well:
- reverse osmosis treatment and filtration systems;
- pumping unit;
- pipes and valves, including those with electric and pneumatic actuators;
- automatic control unit.
In the side walls there are technical holes for conducting electrical wires and waterways.
Caissons are round or quadrangular. The first section should be at least a meter, otherwise a person will hardly be placed inside the caisson. Sizes are calculated according to needs. An excessively small structure will be inconvenient for the installation of equipment and repair work. The overall structure is too expensive.
Without caisson tanks, downhole outlets are only equipped in warm rooms. Additionally, you need to install a downhole adapter - a compact adapter mounted in the casing. It is easier to equip it than a caisson, but further prevention and inspection of the well will be more difficult.
Types and designs
Caissons are made of reinforced concrete and reinforced concrete rings, brick, plastic, metal and polymer-sand mixture. Performance is largely dependent on the material used to produce the sealed chamber.
Reinforced concrete structure
A caisson made of reinforced material or reinforced concrete rings for a well is strong and durable. The first option involves the manufacture of structures with their own hands. A base is prepared on which iron reinforcement is mounted for the walls, and then filling is in progress. In the second case, concrete rings made at the factory are laid on the equipped base, and a plate with a cover is installed on top.
What is a good caisson made of concrete:
- durable and durable;
- resistant to mechanical stress and soil movement;
- weighs a lot.
The latter indicator does not allow the caisson to emerge during the rise in the level of subsoil water, and therefore the structure does not require additional fastening in the ground during installation.
A lot of weight is both the advantage and the disadvantage of a structure. Installation of rings is impossible without the use of special equipment, transportation is also associated with difficulties.
Concrete also absorbs moisture, penetrating into the caisson and destroying its walls. In order for the structure to serve longer, it is necessary to qualitatively waterproof it.
The disadvantage of a concrete caisson is poor thermal insulation. To create a temperature suitable for the operation of the equipment, you need to insulate the camera.
Brick building
Similar advantages and disadvantages are in the brick caisson. It will take much longer to build, but during the construction you can use broken and used material.
The advantages of brick structures include:
- high reliability and durability;
- relatively low thermal conductivity;
- profitability.
At a price, a brick caisson, especially if it is made of used material, is cheaper than all other options.
The minuses also include the ability of the material to absorb moisture, which leads to the need for waterproofing.
Metal product
It is a large metal box with threaded bushings welded into the walls for laying communication lines. It is made of sheet metal, with a thickness of 3-4 mm, better than steel. Aluminum caissons are less durable, but cheaper.
By design, the metal caisson is simple, reliable, tight, and durable. The flexibility of the metal prevents cracks in the structure. Mandatory quality insulation is required.
A heavy metal structure is resistant to swelling of the earth. It does not require additional fixing during installation. But with the installation due to the severity of the capacity will have to tinker. The minuses also include susceptibility to corrosion and high thermal conductivity.
Plastic caissons
Lightweight, easy to install, last a long time, are not afraid of rust, are completely tight. Plastic has good heat-shielding performance, and therefore it is often used without additional insulation, it does not need to be protected from underground water. One of the most inexpensive options: the price is much lower than that of a metal caisson for a well. The cost of low-cost mini-structures made of polymers starts at 1000 rubles, and the cheapest metal tank costs about 9000 rubles.
A plastic caisson for a well consists of two parts: a super-caisson and a caisson. The first may be of a smaller section. A distinctive feature of the structures is the crimp sleeve, which ensures the tightness of the casing joint with the caisson tank. The kit may include special nozzles used for laying wires, pipes for water and other elements to facilitate operation.
Polymeric products have two drawbacks: susceptibility to deformation and buoyancy. They should be mounted on a specially equipped concrete pillow.
Polymer sand options are similar in quality to plastic ones, but they are more resistant to deformation. The rigidity required for the operation of the caisson is obtained by adding sand to the polymer matrix.
Installation of finished structures or DIY
Do it yourself with your own hands is the easiest way to create a brick caisson, since working with concrete rings will require the involvement of special equipment. Before starting work, it is worth making a drawing to visually represent the future structure. For the construction of a caisson, a concrete base is prepared, on which brick walls are further built, and a ceiling with a hatch is installed on them.
There are two options for arranging such structures: with filling and without it. In the first, they dig a pit, larger in size than the future design. When the walls of the caisson tank are erected and dry well, the voids are covered with earth. In the second method, the foundation pit is prepared exactly according to the size of the future structure. Bricks are laid out on the wall, however, there is no guarantee that there will be no empty spaces behind them. The backfill method requires a lot of labor, but the capacity is better and lasts longer.
The structure is erected to a height of about two meters to make it convenient to work, install equipment and deepen the tank below the freezing point.
As for the placement of the finished product, it will also require a pit, the size of the caisson is at least 30 cm smaller. This contributes to a more accurate installation with adjustment of the coincidence of the borehole pipe and the sleeve under it. It also makes it possible to insulate walls or strengthen, which is necessary for a container made of plastic.
Installation of metal containers is carried out in the following sequence:
- Before installation, the external part is waterproofed. It is primed and insulated inside.
- The basis is created - a sand cushion with a concrete slab on top.
- The downhole pipe is cut to size.
- A caisson is placed over the pit on the bars or channels and is adjusted until the casing and the sleeve match.
- Complete installation of the caisson tank.
- Trenches break out to bring water.
- For inputs in the walls of the caisson tank, bushings are welded. Fitting parts are screwed into them with a conclusion to the necessary consumers.
At the end, additional thermal insulation and hydraulic protection are carried out, the tank is covered with earth.
Installing a plastic structure is very similar to installing a metal box. The difference is that when sealing the connection of the borehole pipe with the sleeve, it is not welding that is necessary, but PVC glue. Pipes pass through walls not through threaded sleeves, but through special couplings closed by sealing plugs.
An important feature of plastic is that there is no need for isolation from water and cold, but indispensable protection against soil compression is required. The void between the walls of the pit and the tank is poured with concrete. Also, a plastic container must be fixed with anchors on a concrete base.
Maintenance and operation
A properly assembled caisson rarely needs maintenance. In concrete and brick chambers, additional insulation from the inside or waterproofing may be required.
For thermal protection of the inner walls, instead of traditional polystyrene and polystyrene, foam polyethylene can be used - there is no ground pressure on it.
Due to the presence of welds, metal devices are most often susceptible to loss of tightness - in this case, they are internally welded with special expensive electrodes designed for welding in environments with high humidity.
Caissons are an element necessary for a high-quality arrangement of a well. When choosing the appropriate option, consider the features of the terrain, wells and financial capabilities.
