Welcome to Pro Drainage Group, the United Kingdom’s prime specialists in domestic and commercial sewage treatment plants. We’re proud to be renowned as the country’s foremost authority in installing, repairing, and maintaining all kinds of sewage treatment plants.
A drainage field is one of the least visible parts of a wastewater system yet it is one of the most important. For homeowners across Dorset and the wider South Coast, where ground conditions can vary from chalk to clay within a short distance, understanding how much land is required is essential for both compliance and peace of mind. Many property owners only discover the significance of a drainage field when they begin planning a sewage treatment plant installation or when they experience issues caused by an undersized system. This guide aims to remove uncertainty and provide clear, reassuring information that helps you plan confidently and compliantly.
A drainage field protects the environment by dispersing treated wastewater safely into the ground. If it is too small, poorly designed or placed in unsuitable soil, it cannot function as intended. This can lead to ground saturation, odour, pollution and in some cases costly legal consequences. The size of the drainage field is therefore not a guess but something calculated carefully and in accordance with established UK regulations. Although it might sound technical, the underlying principles are easy to understand once explained clearly.
Contact usA drainage field is a network of shallow trenches that contain perforated pipes laid over clean gravel. These trenches allow treated wastewater to seep gently into the surrounding soil where natural aerobic bacteria continue to break down any remaining impurities. Unlike a soakaway, which is designed to hold and disperse rainwater, a drainage field is specifically engineered for wastewater with strict rules to ensure the protection of nearby watercourses and groundwater.
A compliant drainage field spreads the water over a sufficient area to prevent overloading the soil. The aim is to give the ground enough time and oxygen to carry out the final purification stage before the water reenters the natural environment.
Contact our TeamDrainage fields must comply with British Standard 6297 which sets out the requirements for their design and construction. The Environment Agency also outlines expectations for the safe discharge of treated wastewater, and local authorities may have further planning conditions particularly in environmentally sensitive parts of the South Coast.
These regulations ensure that wastewater is dispersed safely. They also protect homeowners by providing clear rules that guide the installation process. Any new or replacement drainage field must respect these standards and failure to do so can lead to enforcement action, environmental damage or the need for expensive remedial work.
Get in TouchThe question of how much land is required cannot be answered without carrying out a percolation test. This test measures how quickly water drains through the soil. The results vary widely even across short distances and Dorset provides a perfect example of this. Chalk areas can drain too quickly while clay areas drain very slowly. Both extremes have implications for drainage field design.
A percolation test involves digging small trial holes, soaking them, and then timing how long it takes for the water level to fall. The test produces a value known as the Vp which represents the percolation rate. This figure is used directly in the calculation that determines the length of the drainage field trenches.
If the soil drains too slowly or too quickly the site may not be suitable for a drainage field at all. In such cases an alternative solution must be considered.
Book in TodayIn some cases even a large plot of land cannot support a drainage field. This tends to occur in areas with heavy clay or in locations where groundwater levels are high for much of the year. Parts of the South Coast experience fluctuating water tables and seasonal flooding which may influence site suitability.
If a drainage field is not appropriate a professional team can advise on alternative solutions. The key is to ensure the long term safety and compliance of the wastewater system.
Call us TodayHow long does a drainage field last
A well designed drainage field built to current standards can last several decades. Longevity depends on correct sizing, proper soil conditions and regular maintenance of the sewage treatment plant.
Can a drainage field be placed under a driveway or patio
No. A drainage field must be in open ground so that oxygen can reach the soil. Solid surfaces prevent the natural treatment process from functioning.
Can the size be reduced if the treatment plant is highly efficient
No. The regulations require the drainage field to be sized according to percolation results and population numbers regardless of plant efficiency.
The amount of land needed for a compliant drainage field is determined not by guesswork but by the ground beneath your feet. For homeowners in Dorset and across the South Coast this means the only reliable answer comes from a proper assessment carried out in line with British Standard 6297. Once the soil behaviour is known the drainage field can be sized and designed confidently.
If you would like friendly guidance on understanding your site conditions or planning a compliant drainage field, the team at Pro Sewage Treatment Plant is always ready to help when you need them.
Contact us Today