how does a land drain work

Land drains work by allowing water to flow into a pipe in waterlogged areas. When soil is saturated either due to the type of soil or how much rainfall there is, no more water can be absorbed so the ground becomes waterlogged.

Full Answer

What is a land drain used for?

Unperforated land drain is used for distributing surface water, these pipes have no holes; they are used to redirect water to a watercourse such as a stream, river, water tank or soakaway. Land drain should only be used for surface water drainage, never for foul water. Where should I use land drainage?

Where does the water from a land drainage system go?

The water from a land drainage system is taken to usually 1 of 3 possible places. It can be directed to a nearby water source like a stream or river, with permission of the Environment Agency. Land drain water can be directed to a storm drain and it can also be directed to a soakaway system in an area where the soil is more amenable.

How do drainage pipes work in agriculture?

Excess water from the crop root zone can enter the pipe through the perforations and flow away from the field to a ditch or other outlet. Until the 1970s, most subsurface drainage pipes were made from short, cylindrical sections of concrete or clay called tile.

Why do we need land drains in retaining walls?

If voids are created in the ground for any reason they tend to fill with water. Also the static loads on any subterranean structure and retaining walls can be massively increased by the presence of water in the surrounding ground. Land drains are introduced to relieve this pressure.

How deep do you lay land drains?

Land Drain should be laid in a trench that is approximately 250mm wide. Depth may vary according to the particular soil makeup but an ideal depth is 900mm. The sides of the trench should be vertical or tapered in towards the bottom.

How does perforated land drain work?

Perforated land drain is used to collect water through the small holes located around the pipe; these holes allow water to seep from the ground into the pipe and be carried away or to percolate back into the soil at a practical rate.

How do you hook up a land drain?

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How do you unblock a land drain?

If you want to tackle the blockage yourself, you can use a drain rod or plumber's auger – also known as a plumber's snake. If the cause of the blockage is debris and leaves, simply put some protective gloves on and remove the debris manually.

What is the difference between a land drain and a French drain?

Essentially, they are all the same thing. However, French drain more typically refers to the process of removing the surface water by installing a trench and backfilling with gravel. Before there was such a thing as a land drain pipe, this method was called a French drain - without a pipe.

Can I connecting land drain to sewer?

Land drainage can be connected to the standard drainage of a surface water sewer in a number of ways. Catch pits, the preferred method, were discussed above , but where a catch pit is not feasible or deemed not necessary, direct connection can be made...

Do land drains work in clay?

Land drains, commonly known as perforated drain pipes, are used in domestic, commercial, agricultural and industrial areas to stop the ground from being waterlogged. The ground can be waterlogged due to excess water and rainfall or due to impermeable types of soil such as clay.

What is an underground drain called?

SEWER. a waste pipe that carries away sewage or surface water.

Why does my outside drain keep blocking?

If your drain is outside it will most likely have been caused by a build-up of dead leaves, or even tree roots which can find their way into pipes and cause a barrier to the flow of water. If it's an indoor blockage, it could have occurred because of heavy materials or objects being flushed down the drain.

Why is my outside drain overflowing?

If you see that an outside drain is overflowing, this usually means that there is a blockage somewhere between the interior plumbing and the outside drain, or, an external blockage from outside debris. If an outside drain is actively overflowing, this is a problem that immediately needs to be addressed.

How do you clear an outside drain block?

Use a drain plunger. Pour down a mix of baking powder and vinegar, followed by hot water. Use a drain snake or unbent wire coat hanger. Unscrew the U-bend and physically put out any blockages you see.

How do you install a perforated land drain pipe?

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When should you use a perforated drain pipe?

Perforated drain pipes are most commonly used to move rainwater away from the house so that it can drain elsewhere. Commonly situated near the base of your home's foundations, perforated drain pipes help provide optimal drainage for your property so that the likelihood of standing groundwater is significantly reduced.

How deep should perforated pipe?

Installing a Perforated Drain Pipe. 1. Dig a trench that is about twice the width of the drainage pipe. In addition, make sure that you dig at least two-feet deep.

Should I use perforated corrugated pipe for drainage?

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How do land drains work?

Land drains work by allowing water to flow into a pipe in waterlogged areas. When soil is saturated either due to the type of soil or how much rainfall there is, no more water can be absorbed so the ground becomes waterlogged. Thanks to perforations in a pipe and a layer of aggregate, water flows naturally down the aggregate and into the perforations of the pipe.

Where should a land drain be installed?

A land drain should be installed in any areas of significant waterlogging or where the soil has performed badly in a percolation test. A local drainage company will be best placed to advise any DIY or domestic areas if their garden or land is at risk of waterlogging by performing a percolation test. You’re able to perform a DIY percolation test but for large swathes of land it’s not worth the risk when many companies may offer you a test for free. Below is a picture of compacted clay soil.

How to prevent soil from entering drain pipe?

When installing a land drain it’s best to choose 1 of 2 methods for preventing soil from entering the pipe. This will cause a build up of sediment either in the pipe or in the soakaway or water course and eventually cause issues. Choose between a catch-pit or using a non-woven geotextile around 100mm above the top of the land drain. (Some brands offer a pre-wrapped coil pipe but this could limit diameter and length choices.)

What is a twin wall drain?

Twinwall land drain pipes are recommended for use with applications where the weight on top of the pipe may be substantial. For example, this could be where the land drain will be below a driveway. Twinwall pipes are more robust and stronger due to their rigid design.

What is the size of a land drain?

Both types are manufactured from PVC and come in a variety of diameters and lengths fit for different applications. The most common coil sizes are 25m and 50m in length although larger, specialist lengths are available from certain manufacturers.

What is the recommended gradient for a land drain pipe?

The recommended gradient for land drain pipe is 1 in 150. The gradient should certainly not be any more than 1 in 100 as the water flow will too fast and too aggressive.

Why are underground drains used?

Land drains, commonly known as perforated drain pipes, are used in domestic, commercial, agricultural and industrial areas to stop the ground from being waterlogged. The ground can be waterlogged due to excess water and rainfall or due to impermeable types of soil such as clay.

What is the purpose of a land drain?

The purpose of a land drain is to allow water in wet or swampy ground to rapidly drain away or to relieve hydrostatic pressure. They are subterranean linear structures which are laid to a fall which should be as steep as practicable. They are used in agriculture and in building construction sites. Modern land drains take the form of a perforated or discontinuous (i.e. open-jointed) pipe. Typically, the land drains conduct the surplus water to an open ditch or natural water source.

Why do we need land drains?

The purpose of land drains in building construction is somewhat different. If voids are created in the ground for any reason they tend to fill with water. Also the static loads on any subterranean structure and retaining walls can be massively increased by the presence of water in the surrounding ground. Land drains are introduced to relieve this pressure. Traditionally, the drains were created by backfilling behind retaining walls etc. with rubble and allowing the water to drain through the rubble to some suitable point.

How to stop water from flowing through a pipe?

Holes or gaps have to be left in the pipes to allow water to transfer from the subsoil to the pipe and these tend to block with soil or allow silt into the pipe, so blocking it or reducing the flow of water. This can be partially overcome by surrounding the pipes with gravel. However, with time even the gravel becomes choked with soil/silt, so in the latest practice, the gravel is surrounded with a geotextile material which filters out soil particles. Ideally, land drains are laid with access points so that high pressure water jetting is possible to clear silt. However, whatever the technology, all land drains have a finite life and eventually become ineffective due to the ingress of silt and/or the blocking of the surrounding filter media.

How are land drains formed?

Traditionally, land drains were formed in clay soils and peats by excavating a trench and forming a "tunnel" using flat stones. This was very labour-intensive but could often be done using free materials at hand. Typically they were two to three feet (600mm-900mm) below the surface. Agricultural land drains have to be installed sufficiently deep to avoid plough damage. In 1843 in England short earthenware pipes were first used laid edge to edge. The earliest type consisted of a "u" shaped trough onto which a flat lid was placed. Later the extruded clay pipe was developed. These are still used. These can be laid in an excavated trench, or a horizontal hole is formed in the ground using a mole plough and the pipes are forced in by means of a hand or mechanical press. By this means, heavy wet soils, bogs and swamps could be rendered amendable to agriculture. Virtually all crops need a well-drained soil to grow well.

Can you install a land drain on a highway?

Instead of having open ditches at the side of highways, land drains can be installed. The excavated trenches are completely filled with gravel (i.e., no soil cover). This is far safer than open trenches if a vehicle should run off the highway.

How does water travel through a land drain?

Gravity takes hold and the water then picks up speed, channelling downwards and into the land drain itself via the perforations in the pipe. Once inside the pipe, which is laid at a gentle gradient, the water is then free to flow away unhindered to the point of disposal.

What is land drainage?

Land Drainage is the term given to perforated drainage pipes that are used to cure waterlogged areas in gardens or other landscaped areas such as sports fields. Essentially they are perforated pipes that allow water to enter through small perforations. The water then flows away to a more suitable disposal point such as a stream, a storm drain or a soakaway. You should always check with your local authority to confirm that your chosen point of outfall is permissible. Land Drains should never be connected to a combined or foul drain without the express permission of the Local Authority, and in such circumstances the connection must always incorporate a trap.

What fall should the Land Drain pipe be laid to?

Only a very gradual fall is required for land drainage. 1 in 150 is ideal, and certainly no greater than 1 in 100.

How to make an outfall to a ditch?

The outfall to a ditch or watercourse should be made via a rigid pipe (PVC is fine) that is concreted into the bank and extends out above the bank below. The area of bank directly below the pipe should be protected from erosion from the water flow. Whilst most Local Authorities will usually provide a specification for this, the detail is usually some sort of stone facing.

How does gravity affect land drains?

Gravity takes hold and the water then picks up speed, channelling downwards and into the land drain itself via the perforations in the pipe. Once inside the pipe, which is laid at a gentle gradient, the water is then free to flow away unhindered to the point of disposal.

How to prevent soil particles from entering land drain?

If you have not used a geotextile membrane to prevent soil particles from entering the land drain you may wish to consider installing a catch pit. This is essentially and empty chamber with an inlet on one side and an outlet on the other side, slightly lower down than the inlet and protected by a baffle. Any grit or sediment is collected at the bottom of the pit and this can be removed at regular intervals. A typical catchpit is constructed from brickwork laid on a concrete base, with the inlet and outlet pipes built into the opposing walls.

What is the diameter of a land drain?

Types of Land Drain. Most land drains today come in the form of flexible coils made from PVC. The diameter of these pipes varies from 60mm to 150mm, although 80mm and 100mm are the most popular sizes for domestic applications. Coil lengths are generally 25m or 50m, although 100m coils are available in some of the sizes.

How does a drainage system help crops?

Agricultural drainage systems usually increase crop yields on poorly drained soils by providing a better environment for plants to grow, especially in wet years.

How to understand hydrology of drainage?

A first step toward understanding the hydrology of drainage is understanding how much water can drain from the soil profile by subsurface drainage. The amount of drainable water in the soil depends on the soil’s amount of drainable pore space or drainable porosity (Pd).

How do plants extract water from soil?

Plants can easily extract water from a soil when its moisture is at or near field capacity. However, as a soil begins to dry out, increasingly stronger forces hold the pore water until plants can no longer extract any water from the soil. This state of soil moisture is the wilting point of a soil.

How deep are subsurface drainage pipes?

Figure 1: Subsurface drainage pipes are typically placed at depths of 3 to 4 feet in poorly drained soils.

Why is subsurface drainage important?

Once a crop has been established, subsurface drainage greatly reduces the risk of crop water stress from ill-timed or excessive rainfall. For these reasons, subsurface-drained soils represent some of the world’s most productive soils. More benefits and effects of drainage.

What is the bulk volume of soil made of?

Figure 4: Soil bulk volume made up of solids and pore space. Soil water is held by capillary (pore water) and adsorptive (film water) forces.

What causes the water table to drop the distance from its initial position at one to its final position at two?

Figure 8 shows that drainage causes the water table to drop the distance “h” from its initial position at one to its final position at two. The curves marked one and two are precisely the same curves as described in Figure 7, showing the proportions of air- and water-filled pores above the initial and final water tables, respectively. The area between the curves illustrates the volume of pores that have been drained.

What Is A French Drain?

A French Drain is a pipe that collects and directs water. A wide, perforated pipe placed in the ground collects excess water and drains it away from the affected area. The pipe is covered with gravel or rock so that it’s not visible, and it’s angled downward to make sure drainage is smooth.

Why is my French drain angled downward?

The pipe is covered with gravel or rock so that it’s not visible, and it’s angled downward to make sure drainage is smooth. Open ditches and stormwater drains manage rain-flow and excess water near roads, but you don’t want an open ditch near your building or house. A French Drain system is less open, but still allows water to drain ...

Why do you have to calculate the dispersal of water?

You have to calculate the dispersal carefully because you want to drain water away from your house or yard quickly but also keep the water level in the pipe itself low. Many people lay the perforation holes in the wrong place. You want them facing downwards at all times to keep that water level low.

What is a collector and interceptor drain?

Collector and Interceptor drains direct groundwater and surface run-off towards the same drain. It quickly handles surface water to prevent flooding or ground upheaval, but should have a filter because of the shifting earth and debris. Otherwise, you have problems with the pipe further down the line.

Can you nick a gas line while burying a French drain?

Nicking a gas line or sewage pipe while you’re burying a French Drain can cost you a chunk of change to fix and ruin the goodwill of your neighbors.

Do all French drains look the same?

Not all French Drains look the same. Depending on your needs, you have a few options. Traditional French Drains, sometimes called Curtain Drains, follow the directions above. They use gravel and perforated pipe to collect water and it’s covered in earth and vegetation. They’re the least obstructive.

Can I Install A French Drain Myself?

We are huge fans of DIY, but we recommend you call a professional to install a French Drain. Here’s 4 reasons why it is important to find a professional you can trust:

Overview

In agriculture

Modern land drains

In building construction

As part of highway construction

Problems