We install caissons for new and existing boreholes in Riga and the Riga region and choose the caisson by the groundwater level, not from a catalogue. If the groundwater rises high in spring, a borehole adapter is often better than a caisson. In your request, say whether the borehole already exists and what the groundwater level is in spring, if you know.
When a borehole needs a caisson
A caisson is needed if the equipment cannot or should not go in the house: the house is far from the borehole, it has no utility room, the borehole is used for watering or for several buildings. Or you may want to be able to lift the pump without digging out the top of the pipe. In a caisson it is easy to replace a valve, switch or pump, because there is a hatch above the borehole head.
If the house is close and has room for a pressure tank, the simpler solution is an adapter in the pipe wall. A comparison of both options and the rest of the equipment: borehole equipment.
Plastic, concrete or metal caisson
| Caisson type | Advantages | What to watch out for |
|---|---|---|
| Plastic (polyethylene) | Sealed body, light, quick to install | High groundwater can push it up, so it needs anchoring or a concrete ballast |
| Concrete rings | Heavy, does not float, durable | The ring joints must be sealed, otherwise water seeps in during spring; machinery is needed to lift the rings |
| Metal | Durable, can be made to the required size | Must be protected against corrosion, and more condensation forms on it |
The lid and hatch must be insulated, because through an uninsulated lid frost gets into the caisson even if the bottom is deep enough. A caisson needs room to stand in and ventilation, so that moisture does not collect on the electrical connections.
What the building code says
The water supply building code requires the borehole head to be protected from pollution. An underground chamber must be at least 1.8 m high, and the top of the pipe must be at least 0.5 m above the chamber floor, so that water does not run into the borehole in a flood. The borehole head may be placed in a shaft only if flooding is fully ruled out.
In practice this means: if water stands in the caisson every spring, it is not just an inconvenience. Dirty water around the borehole head can get into the borehole, and then bacteria show up in the water test.
Building code LBN 222-15 “Water Supply Structures” (Cabinet Regulation No. 326 of 30.06.2015): point 65 (preventing pollution through the head, head in a shaft only if flooding is fully ruled out), point 70 (underground chamber at least 1.8 m high), point 71 (top of the pipe at least 0.5 m above the floor). The building code covers water supply structures in general, and how each point applies to a private borehole is assessed in the design. Source: likumi.lv, checked 03.11.2026.
A caisson when the groundwater is high
In many places in the Riga region the groundwater rises close to the surface in spring, and then the caisson is the lowest point around, where water collects. Groundwater can lift a plastic caisson if it is not anchored, while in a concrete caisson water seeps through the joints.
- Before digging we find out the groundwater level: from neighbours' wells, ditches or a test pit.
- We anchor a plastic caisson to a concrete slab or backfill it with ballast.
- If the water level is higher than the caisson bottom, we recommend an adapter, not a caisson.
How we install a caisson
- Pit around the borehole We dig a pit around the top of the pipe, taking care not to damage the pipe. For an existing borehole we first lift the pump or secure the delivery pipe.
- Base At the bottom we lay a compacted crushed stone or concrete base, to which the caisson is anchored if needed.
- Installing the caisson We slide the caisson over the pipe and seal the pipe outlet in the bottom. We cut the pipe so that the top is above the floor.
- Connections Through the caisson wall we bring in the water main and cable to the house, and install the borehole head, valves and, if planned, the pressure tank.
- Backfilling and testing We backfill the caisson with soil in layers, fit an insulated lid and check that the joints do not leak.
How much a borehole caisson costs
There is no single caisson price, because it depends both on the caisson itself and on the work around the existing borehole. The price is affected by:
- the caisson type and size: plastic, concrete rings or metal;
- the groundwater level and whether anchoring or ballast is needed;
- whether the borehole is already equipped and the pump has to be lifted;
- access for machinery and the soil to be dug;
- what else goes into the caisson: valves, pressure tank, controls.
If we install the caisson together with all the borehole equipment, we name one total price; borehole equipment starts from €500 without the pump. After your request we clarify the situation and name the price before the work. Other prices: prices.