Caisson for a well: types, purpose, installation and installation technology

The autonomous water supply system solves the problem of providing water to houses located far from the urban infrastructure. An important nuance of the arrangement of such a system is the complete protection of the well against all sorts of negative factors. For this purpose, a special device is installed, which is called a caisson.

Caisson is a chamber designed for arranging the wellhead below the earth's surface. It is constructed above the water intake in order to provide convenient access and the possibility of installing equipment for water supply at home. There are several varieties of such structures. For the developer, who is going to start arranging autonomous water supply, it is important to carefully study all types of caissons for the well and choose the best option for yourself.

Independent installation of the caisson for the well is quite affordable subject to certain rules. Let's try to understand the types of caissons and the rules for their installation.

What is a caisson and what is it for?

Caisson is called an airtight container. Initially, caissons were used for work under water, and later their scope of application was greatly expanded. In particular, such products began to be used to protect the wellhead.

Most often, the owner assumes year-round operation of an autonomous water supply system. However, it is very difficult to do this in conditions of a sharp annual temperature difference. Summer heat and strong winter frosts significantly complicate the operation of the well.

At negative temperatures, water coming from the depth will certainly freeze and ruin, and in the worst case, it will break pumping equipment.

For the smooth functioning of the well, the owner must ensure a stable positive temperature for its tip. The caisson is used for this purpose.

It is an airtight container, which is buried in the ground and fixed on the casing. With additional insulation device will protect the well from low temperatures. In addition, an airtight container does not allow ground and waste water to enter, which can damage sensitive instruments.

In addition, the caisson is the optimal place for the installation of pumping equipment. Here it will be reliably protected not only from the ingress of groundwater, but also from insects and rodents, which can spoil the devices.

Closed caisson restricts unwanted access to the tip.

In addition, inside the structure you can place all the equipment necessary for the operation of a well:

• purification and filtration systems, reverse osmosis;
• pumping apparatus;
• pipelines and valves, including pneumatically or electrically driven;
• automatic, responsible for controlling the pump and the entire plumbing system.

Caisson is a container with a neck, closing the hatch. The height of the structure is usually at least two meters, since the casing enters the structure at a depth of 1-2 m.

Product geometry also varies. In cross section, they can be round or quadrangular. In the first case, their diameter should not be less than 1 m, otherwise it will be very difficult for a person to fit inside the chamber. It is important to choose the size of the caisson.

Too small design will be inconvenient for equipment placement and maintenance and repair. A large camera will cost unnecessarily expensive. Outside the caisson is most often insulated.

At the bottom of the tank, a hole is made into which the casing is inserted. In the side walls are technological holes for laying electrical cables and leading water pipes. In addition, a ladder is installed inside the caisson, the folding option is especially convenient.

It is always interesting to the newly-minded owner of the well, is it necessary to arrange the caisson, because this is a rather expensive event? Yes, you can do without a caisson. But it's not that simple.

Firstly, in this case it is necessary that the well exit falls on a heated room, for example, the basement of a house. This is necessary to protect the equipment from freezing. At the same time, it should be understood that the noise level from constantly working instruments will be high.

Second, have to use downhole adapter. This device is a compact plumbing adapter, which is mounted in the casing.

It consists of two parts. The first is installed on the casing below the level of the GIP, the second is fixed on the water intake pipe. After that, the sliding joint is mounted in “dovetail” with the help of which both parts of the adapter are connected already inside the well.

The device is extremely simple to install and use. In addition, for many well owners, its cost seems to be very attractive, which is much lower than that of the caisson. But we must understand that the installation of the adapter significantly complicates the subsequent preventive maintenance and inspection of the well. In addition, all equipment will have to be located inside the building.

Types of caissons and their characteristics

The shape of the caissons is very different. Round in the plan and rectangular, with the extension at the bottom and without.

Meanwhile, they are clearly divided into three main types of material manufacturing:

• Concrete.
• Brick.
• Metallic.
• Plastic.
• Polymer sandy.

Earlier options with the walls of the wooden frame can now be regarded only as a curiosity or useless exotic because of the high cost, complexity of execution and low consumer properties.

The material from which the sealed chamber is made largely determines its performance. Consider in detail the features of devices made from different materials.

Option # 1 - a camera made of concrete rings or bricks

Until recently, the caisson made of concrete rings can be considered the most common. It is quite simple to make, the construction is strong and durable.

Such caissons are made in two ways. In the first case, reinforced concrete rings manufactured in production are placed on the prepared base. Upon reaching the desired height, a plate with a lid is placed on them.

The installation of reinforced concrete rings is easier and faster than the same work on the device of a plastic or metal caisson, under which you must dig a foundation pit.

The second method involves self-pouring design. The foundation on which the armature is assembled under the walls, and after they have been poured, also for the slab with the hatch, is arranged.

In both cases, the finished design has all the advantages of concrete caissons:

• Undeniable durability and strength. Concrete is a very durable material that successfully withstands strong mechanical stress. Movement of the soil will not affect the integrity of the chamber, cracks on its walls will not appear. The service life of a properly equipped concrete structure is several decades.
• Very significant weight. Reinforced concrete has great weight, which prevents the ascent of the camera when the groundwater level rises. For the same reason, the concrete caisson does not require additional fixing in the soil during installation.

Experts point out that concrete chambers have many drawbacks. First of all, you need to understand that concrete is a hygroscopic material. It absorbs moisture very well, which penetrates into the chamber and destroys its walls. That is why to ensure a long life of the structure should be carried out high-quality waterproofing work.

For processing, you should choose only highly efficient modern materials. Special attention is paid to the joints of the rings, the connection with the concrete base and the place where the casing passes through the bottom of the caisson. Practice shows that it is very difficult to achieve complete watertightness of the structure.

Another disadvantage of the concrete chamber - poor heat insulation. To ensure acceptable temperatures for equipment operation, it will be necessary to warm the container.

The large weight, as in the case of the metal coffer, is an advantage and a disadvantage of the design. Installation of concrete rings is impossible without the use of special equipment, transportation is also difficult. All this significantly increases the cost of installing the caisson, while the price of the rings is relatively low.

In addition, the large weight of the camera adversely affects its operation. Possible over time gradual subsidence of the devicethat will inevitably lead to deformation of the equipment installed in it. The presence of a large number of defects makes concrete caissons little demand. They increasingly prefer other options.

Similar pluses and minuses have brick constructions. True, its construction takes much longer, but in the construction you can use broken and used material.

For the manufacture of the structure, a concrete base is arranged, on which walls are subsequently erected of brick, and a ceiling with a lid is mounted on them. There are two ways of arranging such structures: with filling and without it.

The first involves digging a pit, the size of which exceeds the future caisson. After the walls of the chamber are laid out and dry well, filling of voids with primer is performed. In this case, behind the walls of the caisson does not remain empty places into which rain water can be poured.

The option without backfilling involves preparing a pit, the size of which exactly corresponds to the future construction. When laying bricks adjacent to the wall, however, there is no guarantee that there will be no voids behind them. The first option is considered more time-consuming, but also better and more durable.

The advantages of brick caissons include:

• High reliability and durability. Competently built brick wall is able to endure serious mechanical effects. It has sufficient strength to resist possible ground movement. In addition, a large mass will not allow the structure to float to the surface; additional fastening during installation will not be required.
• Relatively low thermal conductivity. The walls of the bricks poorly conduct heat, therefore, have a good resistance to low temperatures. Such caissons retain heat, so additional warming of the structure is required only in areas with very harsh winters.
• Significant advantage - cost. The cost of a chamber made of bricks, especially if it is composed of used material, cannot be compared with plastic, concrete or metal counterparts. The price of brick caisson is much lower, which is very attractive for well owners.

Today, reinforced concrete and brick structures are increasingly giving way to metal and plastic colleagues. Delivery of positions is justified not only by the speed of installation, but also by the price of structures completely prepared for installation.

Option # 2 - metal caisson

This is, in fact, a large metal box, into the walls of which are threaded bushings for the passage of communications. Most often it is made of sheet metal, the optimum thickness of 3-4 mm. The best option is stainless steel. But it seriously increases the cost of construction. Sometimes there are more curious designs of aluminum.

Metal caisson is fairly simple, reliable. Easy to install, serves for a long time. Very strong construction, with certain skills and the availability of tool park can be made independently. Requires mandatory high-quality insulation.

When choosing or designing such a device, it is important to pay attention to its shape. Ideally, it should be such that the welds are as small as possible and they are of the highest quality possible. The slightest defect in the seam will lead to a subsequent loss of tightness of the caisson.

The use of metal containers due to a number of advantages:

• High strength and flexibility. Steel is a very strong and tough metal, which guarantees the integrity of the body of the caisson during any, even the most significant ground movements. The flexibility of the material prevents the occurrence of cracks in the structure. Plastic containers in this strongly lose metal.
• Long service life. Practice shows that, on average, the lifetime of high-quality metal caissons is about 50 years. This is quite comparable with the life of the well itself. Thus, a properly installed and properly operated capacity will be enough for the entire period of operation of the water supply source.
• Unnecessarily large mass. Heavy metal chamber is characterized by resistance to ground heaving. It does not need to be further fastened during installation. Under no circumstances such a caisson will not squeeze to the surface. Moreover, it will not pop up itself, which happens with poorly fixed plastic analogues.
• Necessary and sufficient tightness. Competently equipped metal caisson is hermetic. It reliably protects the equipment located in it from overhead and from groundwater.

There are metal products and disadvantages. The most significant - susceptibility to corrosion. To avoid trouble, you should regularly cover the walls of the chamber with a fresh protective layer of paints and varnishes. From the inside it will be very easy to do, but from the outside it is almost impossible.

Processed as the inner and outer surface of the chamber. And at the seams fit at least two or three layers of paint. Products made by yourself should be treated in the same way.

Another minus - high thermal conductivity. This makes it necessary to arrange an additional insulating layer not only for the cover, but also for the entire structure.

Significant weight, which belongs to the advantages of metal caissons, can also be attributed to their disadvantages. Impressive weight of the design seriously complicates its transportation and installation, which is often impossible to implement without the involvement of special equipment.

The cost of steel products manufactured in the factory is higher than that of plastic counterparts. Therefore, you can find a large number of metal caissons made in the home, for the quality of which it is impossible to vouch.

Although welded seams are of good quality, they can crack when metal is deformed. Therefore, even if the metal caisson is made of stainless steel, it still requires waterproofing. Black metal is covered with waterproofing necessarily. At the same time, even if the insulation is glued very tightly and does not pass water, it is not regarded as a waterproofing.

Simply put like this: first to the walls outside heat insulation - foam glass, extruded polystyrene foam or something similar - fibrous materials are not suitable here. Then the structure is pasted over with a waterproofing or similar material.

Option # 3 - plastic caisson

The most modern can be considered caissons of polymers. Their plus in the low cost, ease of transportation and installation, durability. Plastic has good thermal insulation characteristics, and therefore is often used without additional thermal insulation, it does not need protection from groundwater.

For the production of such caissons, three types of polymers are used: polyethylene, polypropylene and fiberglass. For the manufacture of plastic containers can be used in two ways:

• Extrusion welding. Tight and durable seam is formed under the pressure of hot air. Especially effective when working with grooved surfaces.
• Rotational formatting. As a result, cast tanks with a solid body are obtained. Seams are absent that provides full tightness.

Plastic chambers usually consist of two parts: the supercamera and the caisson. The first may have a smaller diameter. A distinctive feature of the design is a crimp coupling, which ensures the tightness of the section connecting the casing with the caisson.

Capacities can be completed with the special branch pipes intended for input of cables and water pipes. Plastic borehole caissons have many significant advantages:

• High corrosion resistance. Plastic is not susceptible to the damaging effects of corrosion, which allows containers made of it to serve 50 years or more. In addition, the cameras do not need additional anti-corrosion treatment with special tools. This saves money and time of their owner.
• Full tightness. The camera, made of polymer, is completely sealed. For technological holes, a special hardware has been developed that provides complete protection against moisture. Thus, additional waterproofing of the water-pressure side of the structure is not required. Whereas for caissons from other materials, for example, reinforced concrete, this is a prerequisite.
• Low weight. The design has a low mass, which greatly simplifies the process of its installation and transportation. Installation of a plastic caisson can often be carried out without the involvement of special equipment, which allows you to save a lot. This is not possible when installing a concrete or metal structure.
• Sufficient tank stiffness. The manufacturer has the ability to vary the thickness and shape of the walls in plastic caissons, creating designs with a given stiffness. Available in models with internal stiffeners, which increase the strength of the vessel. By the way, you can pick up modifications with a reinforced base, designed to work in conditions of high groundwater levels.
• Good thermal performance. Plastic has a low thermal conductivity, so in most climatic zones, the walls of the caisson will not need to be further warmed. Only the container lid needs protection from the cold. If the caisson will be operated in areas where severe frosts are possible, it is worthwhile to insulate its walls.
• Possibility of equipping with additional elements. Manufacturers of plastic containers offer a variety of items that will make the operation of the caisson convenient. This may be an additional internal staircase, a special shelf under the insulation for the lid, a folding aboveground part that facilitates the descent into the structure, and much more.

Among the shortcomings of plastic containers, two are worth noting. The first - susceptibility to deformation. To level this lack it is necessary to select a caisson under the type of soil. On sale you can find various modifications with wall thickness from 10 to 40 mm.

In addition, it is possible to replace the outer soil filling with a cement casting. Its width can vary in the range of 80-100 mm around the perimeter of the caisson. Another option - filling with sand and cement mix. Experts recommend using 5: 1 ratio.

The second disadvantage is plastic buoyancy. You can get rid of it by equipping a cushion of concrete at the base of the tank. After mounting on the concrete base, you will need to fix the plastic construction, which will prevent it from being pushed out of the ground. All these measures increase the cost of installing such caissons.

Positive and negative sides of plastic caissons:

Option # 4 - Polymer Sand Caissons

Relatively recently on sale teams polymer well wells have become an excellent option for arranging caissons. The container is assembled from several rings, a cone-shaped lid with a hatch and the bottom. It is made of modern composite material, which includes sand and plastic.

The rigidity necessary for the operation of the tank is achieved by adding sand to a matrix made of polymer.

Polymer sand chambers have a relatively low cost and have many advantages:

• Resistance to external influences. Composite material is not susceptible to corrosion, does not enter into chemical reactions, has high strength. It successfully withstands mechanical stress, is frost-resistant and has a very low moisture absorption coefficient.
• Extremely simple installation. The design is produced in the form of elements equipped with thorn-groove locking joints. This allows you to quickly and accurately collect the capacity of the desired size. To install it in place, special equipment is not needed.
• Small weight of individual items. The mass of each of the parts for the assembly of polymer-sand construction does not exceed 60 kg, which makes it possible to assemble the camera together with an assistant. Transportation of rings and other elements of the caisson can be carried out by a trailer to the passenger car.
• Ensuring perfect tightness. A properly assembled polymer sandwich chamber is completely sealed. To perform technological holes in its walls can be used an ordinary household tool. Once pipes have been introduced, the holes must be sealed with any suitable composition.
• Long service life. The manufacturer guarantees that its product will last at least one hundred years without changing its properties. Since the products made of polymer sandwich are still quite “young”, it was not possible to verify this in practice.

However, it is impossible to guarantee tightness at the joints of the structural elements of the container. Therefore, experts recommend before starting the assembly of the camera to try to stumble and lubricate future joints with sealant or usually bitumen mastic. Such a connection would be better to retain moisture.

A little about polymer well, which can be used as a caisson:

General installation guidelines

From an engineering point of view, installing a caisson for a well is required for equipment placement and protection. wellhead from damage, intake into the zone of intake of storm water and pollution.

The caisson for the well is much more advantageous from the standpoint of operating costs - in contrast to ground structures, it usually does not require heating (provided that it is below the calculated depth freezing). Although there is no other option - if it stands higher, it will simply squeeze it out in winter.

Squeeze out the soil can and recessed caisson. Especially in cases where the site has problems with high bedding. Therefore, it is recommended to “anchor” not only light plastic, but also more stable metal systems. Technically, this is done very simply. A concrete slab is poured under the caisson for the well, to which the bottom of the caisson is fixed with anchor bolts.

On high, non-floodplain areas, you can do without a concrete base - a fairly good sand pad. But here, too, the presence of a heavy slab under the caisson does not hurt. Therefore, it is always better to plan it, away from the geological features of the site. In any case, the caisson is placed strictly vertically - compliance with this condition is mandatory.

The height of the structure is about two meters - this size allows you to work comfortably and place the equipment, and deepen the caisson below the freezing depth.

Even if all conditions are met, in the trunk pipes it is not bad to lay heating cable - just in case of force majeure.

The electric cable, the feeding pump and automatic equipment, do not put directly in the earth. It does not require burial, as pipes with water, but it is still necessary to protect it. It has double insulation, but this is not enough. It is better not to use for these purposes corrugation, very popular in the outer gasket. Best of all PND pipe.

The pipe with an electric cable is laid underground shallowly - about 30 cm from the surface. Considerations here are simple - the frost is not terrible, but just in case you need to take care that the communication is not damaged by accident. The benchmark is simple: we dig in more than on a spade bayonet.

The pipe with water is buried deeper - below the depth of frost penetration. Entering the house on the surface it is possible only under the condition of insulating the pipeline section from the level of seasonal freezing to the point of entry into the building. Equipment is better to lift above the floor of the caisson. Slightly, but not necessarily. In case of flooding.

All electrical devices in the caisson must be grounded. And it would be good to introduce into the electrical circuit UZO. Security is never redundant. Rather, it may not be enough.

The casing of the well goes into the caisson through a sleeve that is slightly larger in diameter. For example, taking into account modern assortment, for a common casing with a diameter of 133 mm, a 146 mm liner would be required.

The well pipe should not be flush with the bottom of the chamber - always slightly higher. Excess within 40 - 50 cm. In case of flooding.

The sleeve and the siege pipe at the junction are sealed. The wellhead is put on the well - a special hermetic cap in which there are openings for the cable of the submersible pump and the passage of the HDPE pipe from the pump. The power cable of the pump is also attached to it. The cover protects the wellbore from dirt and accidental debris.

The entrance to the caisson chamber is traditionally made in the form of a hatch. The design depends on personal preference. In any case, the preferred option with two hatches - just for reasons of saving heat.

The exit under a pipe of a well makes the way, as a rule, in a place. It does not have to be clearly centered. It is quite acceptable to shift it, to make it asymmetrical. But here we must remember that the well exit and the caisson hatch must be coaxial - this is very convenient when repairing and installing equipment. Simply put: it is desirable to install the access door directly above the well head.

All about installation and connection

The installation procedure is, in general terms, similar for all types of caissons. Although there are features that will be discussed below.

The pit for the caisson is chosen at least 30 cm more than the caisson itself. This will help and more precisely install it, correcting the coincidence of the well pipe and the liner for its passage. In addition, it will allow to insulate the walls or strengthen, as required by the plastic construction.

As already mentioned, the well casing is trimmed to the future floor height of the chamber. The bottom of the pit is covered with a sand pillow 20-30 cm thick. Sand backfill is shed for compaction. A concrete slab with steel mesh reinforcement is poured over the pillow.

Anchor bolts can be placed on it to secure the caisson in advance. But here is a great chance to make a mistake. Therefore, it is much more convenient to first install the caisson in place, and then drill holes in the plate for fasteners.

Now there are many expanding and wedging fasteners in the holes, and therefore there are no special problems to choose something suitable.

Now let's dwell on the features of this or that structural scheme.

Installation of caisson from concrete rings

The technology is not much different from the installation well rings. Only to a much smaller depth. Rings are fastened together by steel plates - in case of ground movement.

The seams between the rings are filled with cement mortar and ironed - they are coated with pure cement mortar without the addition of sand or other lean components.

Concrete still passes water, albeit not intensively. Therefore, it is necessary in advance to attend to waterproofing the walls of the caisson. Often for this purpose, used ruberoid or polymer films, glued with the mediation of bitumen mastic. The method has the right to life, but it is better to use glassyzol or hydroisol reinforced materials. Or similar to them.

Concrete not bad resists cold and freezing, but still its standard performance is not enough. Additional warming is required. Here it should be borne in mind that the insulation used should not absorb water - otherwise it will be useless. And to resist the pressure of the soil - over time, the soft insulation of the soil can compress to the thickness of the paper sheet.

Therefore, preference is given to the most dense and durable varieties, often the various types of plate insulation. You can recommend foam glass - but this is a very expensive option. More budgetary insulation will be extruded polystyrene foam. Or, as it is called for short, Epps.

The cheapest insulation is likely to be foam. It is easy to work with him and his increased flammability will not play a role when placed in the ground. But it is worse to resist compression and is not very durable - in a few years it will have to be changed.

Not only walls are warmed, but also overlapping. But it is much easier than to insulate the wall. We only take into account that the insulation should not stand out beyond the perimeter of the caisson - otherwise it will simply tear off during shrinkage - the design is still quite heavy.

Another interesting point. Often there are recommendations for concrete caissons not to make the bottom. That is, install the ring directly on the sand pad and gravel drainage. The motivation is simple: in case of condensation, it will go to the soil.

Or the second variant of this solution: do not fill the joint between the bottom ring and the concrete base with cement mortar. The reason is the same - to allow the possible condensate to escape.

Such versions are difficult to recommend for repetition. Going because this scheme will work only on a high dry area. In other cases, the deepening of two meters below the surface of the earth will do its job - the caisson will be flooded at least once a year. And, therefore, will not fulfill its role.

The problem of condensate is solved by normal insulation. In extreme cases, we simply introduce ventilation into the design, as in a cellar.

The absence of a base of concrete under the rings is completely unacceptable - due to the small area of ​​the support. In other words, there is a risk of great shrinkage. Which, in turn, is fraught with the deformation of the incoming pipes. The principle of the approach is simple: everything should serve for a long time and reliably. The fewer adjustments and interventions subsequently required, the better.

Passing pipes through walls is insulated in the same way as inputs through the foundation of a house — cement mortar and bitumen mastic from the outside.

Installation of metal caisson

Installation of a metal caisson necessarily requires a molded base plate and anchorage attachment. Before installing the outside box caisson plastered waterproofing. From the inside it is primed. This is mandatory even for stainless steel. Be sure to warm. A slightly different way to skip communications.

The casing of the well is simply passed through a sealed sleeve to the bottom. Sleeves are boiled for the remaining entries in the walls. They simply screw in the necessary fittings, thus bringing water lines (to the general water supply, for watering the garden, to the pool and so on) and running the power cable to electric pump.

Usually everything happens in the following sequence:

• Dig a pit under the caisson.
• The basis is made - a sand pillow and a concrete base plate.
• It is cut to the size of the well casing.
• A caisson is placed over the pit on the bars or channels and carefully set up until the well pipe and the liner coincide.
• Finally installed caisson in a regular place.
• Auxiliary trenches are digging for water supply to the house and others.
• All communications are connected.
• Hung insulation and waterproofing.
• Caisson closes ground - buried.

In this scheme there may be additions and permutations, depending on the conditions of the site and tasks. But here it is better to dig trenches for the caisson after installation - just jumping at this moment through the extra ditches and pits is not entirely handy.

Installation of plastic caisson

In general, the process is very similar to the manipulation of the metal version. The difference is that when sealing the articulation of the casing with the sleeve, not welding is required, but glue for PVC.

And the passage of pipes through the walls is not done through the threaded bushings, but through special couplings, which are then closed with sealing caps.

An important feature is that waterproofing and insulation are not required, but mandatory protection against squeezing with soil is needed. It is done simply. The gap between the walls of the pit and the caisson is filled concrete mass. No need for high strength composition. A solution of 5: 1 is enough, which means: 5 parts of filler and 1 part of cement. As a filler mixture of sand with rubble.

The measure is necessary, even if the polymer case has stiffeners. But all these efforts are not so high when compared with the previous versions. Moreover, such a concrete shell makes the whole structure stronger and more resistant to extrusion. What affects the overall life.

More details in the photo galleries:

Conclusions and useful video on the topic

The rules for installing a caisson and placing equipment in it are slightly different. It all depends on the type of construction, but it repeats in general terms: the principle itself is important.

Caissons - an element necessary for high-quality arrangement of a well. It is very important to choose the right device, because the operation of the entire system will depend on it. Definitely determine the best caisson is impossible. This must be decided by its future owner. When choosing, it is necessary to take into account the features of the terrain, the well and its financial capabilities.

The rules and subtleties of installing a caisson for a well are not so numerous. Even if the developer is not confident in his own abilities and will not solve the problem on his own, knowledge of the basics will allow him to control the work done at the site by the contractor. After all, the quality of their conduct depends on the comfort of living in the future.

Are you seriously thinking about installing a caisson? Or maybe you have already done this kind of work yourself or have valuable knowledge you want to share with visitors to our site? Please share your experience, leave your comments at the bottom of the article.