Construction of caissons for a well with your own hands from various materials

Recommendation points

• Caisson design
• Making a caisson with your own hands
• Reinforced monolithic concrete caissons
• Pouring the base plate
• Rebar knitting
• Formwork panels preparation and installation
• Pouring concrete walls
• Floor fill
• Installation of the hatch
• Brick caissons
• Steel caissons
• Installation of caissons from reinforced concrete rings
• Installing a plastic caisson

When building an autonomous water supply for a country house, a well needs protection from sand, soil and surface polluted water entering the pipe. Consider the procedure for performing work on the assembly and installation of the caisson, moreover, in several versions using various materials.

To exclude the ingress of contaminants into the aquifer, contain the walls of the well from collapse and protect the water supply equipment from freezing in winter, the well is equipped with a caisson.

There are ready-made metal and plastic caissons on sale, differing in shape and size, but you can equip the caisson yourself, using other building materials.

Caisson design

In order to be fit for purpose, the design of the caisson must be:

• sealed;
• strong and tough;
• have an insulated cover;
• be large enough to accommodate equipment, instruments and the possibility of their maintenance.

In this case, the shape of the device can be one- and two-stage, with a base in the form of a circle or a square.

In the bottom of the caisson, there is a passage under the riser pipe. The side wall is equipped with passages for domestic and outdoor water supply, electric cable, and in some cases – ventilation holes with pipes extending above ground level. When using thin sheet materials, the base, side surfaces and cover must be reinforced with stiffeners. In the upper part of the caisson, a heat-insulated cover is fixed on hinges. Steps are mounted on a vertical surface for quick and easy access and equipment maintenance, and handles are attached to the cover.

Making a caisson with your own hands

The choice of materials for the caisson is primarily influenced by: the laboriousness of installation, the availability and price of materials, as well as the experience of working with them.

At the first stage, earthworks are carried out. It is necessary to dig a pit in such a way that the outlet of the casing is not in the center of the caisson, but is somewhat displaced. This makes it easier to locate and maintain equipment installed in the tank. The bottom of the pit should be 0.5 m below the freezing level of the ground, and its width should be slightly larger than the outer dimensions of the caisson, by 150-200 mm on each side to create a sandy heat-insulating backfill (for thin-walled caissons – metal or plastic).

The internal dimensions of the chamber without installing a pumping station in it can be 1×1 m (O 1 m), with equipment – 1.5×1.5 m (O1.5 m). The wall thickness depends on the selected material and its strength characteristics.

Simultaneously with the preparation of the pit, part of the land is selected for the channels for laying the water supply to the house and to the taps on the personal plot.

Reinforced monolithic concrete caissons

The walls are necessarily reinforced with reinforcement, taking into account the height of the structure and the cost of the well arrangement. It would be very annoying if the collapsed wall caused serious damage to the water supply system of the house. Since it is much easier to make a flat formwork, monolithic caissons are most often made square at the base..

For work you will need:

• cement, preferably at least M400;
• crushed stone;
• clean sand;
• reinforcement with knitting wire or reinforcing mesh;
• waterproofing material for walls;
• timber for formwork;
• insulated cover or materials for its manufacture;
• concrete mixer, construction tools.

1. Sand pillow. 2. Concrete base. 3. The walls of the caisson are made of in-situ concrete. 4. The mouth of the hatch. 5. Ladder. 6. Caisson cover

Pouring the base plate

The base plate may not be reinforced, however, along its perimeter, it is advisable to lay a row of reinforcement with vertically fixed rods to connect the walls with it for reliability. You need to move on to the second stage when the concrete has set enough to be walked on. If the groundwater is located below the level of the caisson bottom, the base plate can not be poured with concrete, but simply compact the soil and pour a layer of sand and gravel.

1. Support stakes. 2. Formwork panels. 3.Sand preparation. 4. Concrete. 5. Fittings

Rebar knitting

The earthen walls are covered with waterproofing material that prevents the soil from shattering and does not subsequently allow the walls to be washed away by melt or irrigation water. Along the perimeter of the caisson, reinforcement is knitted at a distance from the waterproofing equal to half the wall thickness. It is enough to install vertical rods in one row every 0.4–0.5 m, weld them to the embedded concrete base and tie them with reinforcement to adjacent rods. If the rods are laid in the base to the entire height of the caisson, then only a horizontal ligation is required every 0.4-0.5 m. The height of the reinforcement should be sufficient to fasten the horizontal reinforcement cage of the floor on it.

Formwork panels preparation and installation

It is easier to prepare in advance the panels for the formwork of a given size than to hammer in nails in cramped conditions. If the shields are ready, you need to lower them into the pit and fasten them from the inside along the line of the reinforcing cage at a distance equal to half the thickness of the wall, fastening them together. In places where the communications pass, pipe sections are laid or a rectangular channel is fenced with boards. If the embeds are not made (for example, due to the difficulty of sealing the formwork), the wall will subsequently need to be punched through with a hammer drill until the concrete is completely petrified. If you want to embed the steps in the walls, you need to worry about the embedded structures before pouring.

1. External formwork of the walls of the caisson. 2. Internal formwork of the caisson walls. 3. Spacer bars. 4. Concrete

Pouring concrete walls

It is better to fill the walls to the very top in one step or at least in one day. Calculate in advance the required amount of solution and ingredients for its preparation. This avoids horizontal joints in the caisson structure. When filling the formwork, it is necessary to periodically tamp the layers or bayonet with a rod in depth, releasing air bubbles.

After the mortar is poured, you need to install a temporary canopy over the construction site to protect the walls from precipitation. In hot weather, the concrete surface should be slightly moistened to avoid cracking. You can proceed to the next stage in 7-10 days, after the concrete walls have dried.

Floor fill

After removing the formwork, a shield is laid on the walls, made of boards, in which there is a fenced hole for mounting the cover, as well as passages for the ventilation pipe and street water supply. The pipes are inserted into the holes and secured. The shield is covered with a layer of waterproofing material, and on top of it, at some distance from the surface, a reinforcing cage is knitted, fixed to the wall rods. To provide a gap between the frame and the waterproofing, several stones must be placed under the reinforcement. Pour concrete and let it grow stronger.

Installation of the hatch

The formwork is being assembled for the installation of the metal structure of the cover. A purchased cover or welded with oneself from sheet and profile steel, is installed in the formwork and poured with concrete. The formwork is removed, the inner side of the cover is insulated (for example, with foam). The surface of the caisson, in addition to the hatch, is covered with waterproofing and covered with a layer of soil to ground level on the site.

Some useful theory in the video:

Brick caissons

Brick caissons have a similar design. Excavation and floor filling are performed in the same way as in the previous case. If the base plate is not being built, a strip foundation is arranged under the walls with a width slightly larger than the walls and covered with a layer of roofing material.

The walls, and, if necessary, the bottom of the caisson, are brickwork. They are laid out at some distance from the ground to organize insulation from sand, broken brick or crushed stone. Each row of bricks should be laid out, controlling the horizontal level with a level and carefully applying and leveling the cement mortar so that no voids remain in the masonry. In the place of passage of the channel for the water pipe, a mortgage structure is embedded in the masonry.

Overlapping and installation of the cover are performed in the same way as for a monolithic concrete caisson.

Steel caissons

Metal caissons can only be assembled by welding to ensure tightness. The materials used are carbon sheet coated with Kuzbass lacquer or stainless steel 3–10 mm thick. Before work, you need to decide on the dimensions, draw the future structure (with holes, stiffening ribs, feet, slinging loops and, if possible, detail it for ease of manufacture. You can use a corner, channel or kerchiefs.

If you can purchase a pipe with a diameter of 1-1.5 m of the desired length inexpensively, it will serve as an excellent basis for creating a cylindrical caisson. It is easier to weld a tank with a square base from sheets yourself.

At the first stage of production, sheets are cut for the bottom of the walls and the upper part of the caisson, including the hinged lid. Since the sheet is quite thick, it is very difficult to cut it with a hand tool, cutting it with welding or a hacksaw for a long time. Good option: ask to cut the metal when buying according to the dimensions of your design.

When welding, try to perform the seams as efficiently as possible, and then treat the entire surface with an anti-rust agent and open it from the inside with a suitable varnish, and from the outside with bitumen mastic.

Earthworks are no different from previous options. It is impossible to lower a heavy structure into the pit on your own, you will need to rent special equipment or a block device, traction from a car and an assistant directing the caisson to its intended place.

After installing the metal structure on the base plate, a water supply is connected through the holes in the walls, all joints are welded, the lid is insulated. The cavity between the caisson and the earthen walls must be covered with sand, and fertile soil must be laid on top.

Installation of caissons from reinforced concrete rings

The caisson made of reinforced concrete rings at all stages, except for the walls, is made in the same way as of monolithic concrete, but the walls of the structure are made of ready-made elements. Time and effort are saved, but the laying of the rings will require the involvement of special equipment with lifting equipment. The concrete rings are stacked on top of each other on a waterproofing cement mortar. Before installation, it will be correct to prepare a concrete base, especially if due to melt water in the spring, the top water in your area can rise high, lay the waterproofing on the bottom and walls of the pit, and then fix the edges on the neck of the structure. Sand filling and installation of the hatch are performed around, similar to that described above.

Installing a plastic caisson

Plastic caissons made of polypropylene or polyethylene are installed similarly to metal ones, but the joints inside the structure are sealed to the pipes not by welding, but by a mounting sleeve. It is recommended to fill the cavity between the outer side surface and the earthen walls with concrete mortar for greater strength of the structure. After the concrete has dried, the “shoulders” of the reservoir are covered with soil. Sometimes the entire volume around the caisson is concreted.