How to get rid of water in the basement of a private house

Recommendation points

• Why and where does water seep from?
• Lowering the groundwater level by soil drainage at the site
• Water isolation and hydraulic lock
• Local removal of water from the basement

Basement flooding can openly be called one of the most annoying troubles in the life of a private homeowner. We propose to find out the reasons for such phenomena and choose adequate methods of counteracting groundwater. Starting from a temporary solution to the problem, and ending with an integrated approach.

Why and where does water seep from?

Conventionally, the basement is an underground reservoir, which is structurally isolated from the ground and all phenomena occurring in it. Unfortunately, even modern monolithic “containers” of this kind, even with their impeccable technological performance, have a quite foreseeable service life, let alone prefabricated cellars with brick walls! Water at a depth of two to three meters is under pressure and can seep inside even through the slightest gap in the waterproofing.

The situation is aggravated by the dynamism of the soil, which subsides and bends, periodically changing the relief of the clay layer. All kinds of depressions, folds and channels in which water accumulates and flows are hidden from view. All these phenomena become apparent when the top water enters the basement area along the altered path and accumulates in it, finding no other way out.

It is impossible to delay the solution of the problem – every year the resource of the structure decreases, besides, periodic flooding causes wild inconveniences when using the basement for its intended purpose.

Lowering the groundwater level by soil drainage at the site

The first and most obvious way to get rid of the water in the basement is to interfere with the natural processes of geomorphology. The layman may be familiar with such activities as drainage.

The reduction of groundwater level at the site is carried out:

• installation of absorption pipes with perforated walls at the design depth;
• organization of underground pipelines
• reset field device.

In a drainage system, a basic rule of thumb is that in order for a container to remain drained, more water must potentially flow out of it than it flows in. And since the flow of water through dense soil is very slow, several hollow pipes with a diameter of 100-200 mm will be enough even to drain a large area.

The arrangement of the drainage system is quite complicated from an engineering point of view, but the flooding of the basement is only the visible part of the iceberg. It cannot be ruled out that soggy soil can cause rapid aging of other underground structures..

In terms of practical implementation, the prototype of the system is extremely simple. Along the perimeter of the area to be drained, a network of trenches is dug out with a bar or manually, the depth of which corresponds to the desired ground level. The bottom of the trenches is covered with geotextiles and covered with a layer of any hygroscopic material – from vermiculite to ordinary road rubble – or a combination of both. Hidden in the layer of porous bedding are perforated pipes that are resistant to high subsurface pressure and other specific operating conditions.

The pipe system has key points. For example, prefabricated collectors that direct all the water from the site into one channel with sufficient flow capacity. Or revision wells – wide vertical shafts installed at rectangular intersections of pipes for their maintenance, inspection and cleaning with special equipment.

The drainage field should be arranged taking into account the peculiarities of the relief of the first water-resistant layer separating the upper water. The runoff is always directed to the lowest point located at least 25 meters from the border of the drained area. The drop field is a system of pipes connected by a “comb” with an interval of 2.5 meters. The total capacity of the field to drain water should be equivalent to the absorbency of the drainage system.

Water isolation and hydraulic lock

In lowlands and near water bodies, soil drainage will do nothing, the volume of incoming water is too large and there is no lowest point for its discharge. The alternative in this case is the most reliable waterproofing of the basement. It is not always easy to arrange it even at the construction stage, however, there is every chance of making the basement dry.

We are talking about the opening of the soil outside the basement and the subsequent work on waterproofing the walls. It should be noted here that not every basement or basement requires work from the outside. For example, concrete walls and floors can be injected making them completely impervious to moisture.

Otherwise, it is required to dig a technical trench 40-50 cm below the walls, leaving about 70-100 cm of free space for work. At the same time, the bearing layer of the wall is cleaned of fragments crumbled by erosion and is re-plastered to create a solid and even base. Waterproofing is applied to this base: mastics, or roll materials that cut off moisture from the structure of the walls. A protective plate is cast on top of the waterproofing layer, designed to fix the hydro-barrier in the mass of the wall and to reliably protect it from cracks, dents and other influences.

But these are only walls. The floor in the basement for the reconstruction of hydraulic protection is also opened below the depth of the walls and is cast in a monolithic reinforced concrete slab. In this case, the task of the hydro-barrier is performed by a 30–40 cm layer of heavy, tough-plastic clay, moistened and compacted without the formation of cavities. Any durable, preferably seamless material is spread on the hydraulic lock: thick polyethylene, banner fabric or PVC canvas for the pool. The edges are glued with bitumen on the walls with a 100–120 mm fold. For such protection, the floor can be cast with a slab, you can also fill it with rubble.

Local removal of water from the basement

The third method requires certain knowledge in geology, in particular – reliable information about the soil section at the location of the basement or as close to it as possible. Such information can often be given by neighbors under construction or well diggers, it may be worth looking for archived survey results..

The essence of the drainage is to discharge the upper water into the first aquifer. Before environmentalists express their comments, you need to focus on the fact that we are not talking about technical drains or sewerage. Groundwater and melt water follow a similar path to the first aquifer, but they seep through natural faults and gaps in the aquiclude. In addition, water from the first aquifer cannot be used as drinking due to chemical and salt pollution..

A cube-shaped pit with a side of 0.5 m is being dug on the basement floor. In this case, the clay floor is planned with a slope from all sides to the formed cavity and is well compacted. It is possible to create several pits or one drainage trench, depending on the shape and size of the basement.

A hole is drilled in the pit with a handbrake drill with a 50 mm crown. Its function is to connect the basement with the first aquifer or sand pocket, or to reach thick sandy loam or light clay deposits. On average, the well depth can be from 5 to 20 meters. A 40 mm HDPE pipe is inserted into the well – the bottom edge is sealed to a narrowing, in a section 2 meters from it, the walls are often perforated with 8 mm holes. The opposite edge of the casing is cut at the basement floor level and is also perforated. The pit is filled with quartzite crushed stone of fraction 10-15 mm, it also covers the entire floor, with a layer of about 10-15 cm.

A screed with drain and ventilation grates can even be arranged on top of the drainage cushion, but many are satisfied with the bulk floor, possibly with walk-through ladders. It is important that with this method of drainage, the basement is guaranteed to be dry, even if it is located in a flooded lowland..