Drainage Field Installation in Surrey & West Sussex
A properly designed drainage field is an important part of many off-mains wastewater systems.
CH Services installs drainage fields for suitable septic tanks and domestic sewage treatment plants, helping homeowners across Surrey and West Sussex find practical solutions for their property's drainage requirements.
We also offer rainwater drainage solutions, although surface-water soakaways and drainage fields for sewage effluent require different designs and considerations.
What is a Drainage Field?
A drainage field is an underground arrangement of perforated pipes laid in trenches. Wastewater from an appropriate septic tank or sewage treatment plant passes into the surrounding soil for further treatment and dispersal.
You may also hear the term “septic tank soakaway”, but a sewage drainage field is not the same as a rainwater soakaway. Surface-water drainage is designed for a different purpose and must not simply be substituted for a compliant foul-water drainage field.
How We Assess Whether a Drainage Field Will Work
The two starting questions are straightforward: how well does the ground drain, and is there enough usable space?
CH Services carries out percolation testing to understand the soil’s drainage characteristics. The test result is then used alongside the property’s maximum occupancy and expected wastewater flow to calculate the required drainage field area. We assess whether that area can fit on the property while meeting relevant separation distances and site constraints.
For example, drainage fields generally need to be at least 15 metres from buildings under the applicable guidance. Other distances and environmental restrictions also matter, so the final layout needs to be considered as a whole.
A large garden does not guarantee a suitable site. Heavy clay may drain too slowly, groundwater may be too high, or the usable area may be restricted by buildings, boundaries and other features.
When Might You Need a New Drainage Field?
Your existing soakaway or drainage field has failed or is no longer draining effectively.
You are installing a new packaged sewage treatment plant with a discharge to ground.
An existing off-mains sewage system needs upgrading and its present discharge arrangement is unsuitable.
Site assessment shows that a different field layout or correctly sized replacement is needed.
Standing water, soft or persistently wet ground and unpleasant smells can indicate a problem, but they do not prove that the drainage field is the only cause. The wider system needs to be considered before replacement is recommended.
What if The Ground is Unsuitable?
In our experience, wet clay and high groundwater can make excavation difficult and may also affect whether ground infiltration is suitable. Percolation testing and the site layout help establish the options before installation begins.
Where a drainage field cannot be installed appropriately, a different lawful discharge arrangement may need to be considered. For a suitable packaged treatment plant, discharge to a qualifying stream, river or year-round flowing ditch may be possible, subject to environmental requirements and any necessary permissions. This is not an option for untreated septic tank effluent.
What Happens During Installation?
We plan the drainage field layout based on the required area and available space. We then carry out the excavation, install the drainage field and reinstate the disturbed ground as agreed for the project.
Site access matters. Getting machinery and shingle into an enclosed garden may require specialist lifting arrangements. We consider this in advance because access can affect the installation method and the final price.
Recent Drainage Field Installations
We've helped homeowners across Surrey and West Sussex replace failed drainage fields, upgrade septic tanks and overcome challenging site conditions. Explore some of our completed installations.
Drainage Field Installation Near Petworth
A new drainage field and Airseptor conversion at a five-bedroom property, with equipment craned over a three-metre wall to overcome restricted access.
Drainage Field Installation Near Churt
Replacement linear drainage field and Airseptor conversion for a five-to-six-bedroom property, followed by garden reinstatement.
Drainage field guarantees and long-term care
CH Services offers a conditional 10-year guarantee on its drainage field installations. The performance of a drainage field also depends on proper use and maintenance of the septic tank or treatment plant feeding it. Allowing excess solids into the field can cause damage and shorten its working life.
We explain the maintenance considerations for the wider system. Please ask for the specific guarantee terms and exclusions for your installation.
Contact us
For more information, availability or a no obligation quotation, please complete our form and we will be in touch shortly. We look forward to hearing from you.
Email us directly:
Frequently asked questions
How is a drainage field sized?
A percolation test helps establish how quickly water moves through the soil. The result is considered with the property’s maximum occupancy and wastewater requirements to determine the field area needed, subject to other site constraints.
Can you install a drainage field in clay soil?
It depends on the test results and wider site conditions. Clay often drains slowly, and heavy, wet ground can make installation more difficult. A drainage field should not be assumed suitable without proper assessment.
Does a sewage treatment plant always need a drainage field?
No. A drainage field may be appropriate for discharge to ground. A suitably treated discharge to a qualifying watercourse, such as a stream, river or year-round flowing ditch, may be an alternative when the relevant rules and permissions allow it.
Is a drainage field the same as a rainwater soakaway?
No. Drainage fields serve sewage effluent from suitable treatment systems; rainwater soakaways manage surface water. The design standards and environmental considerations differ.
How much does a new drainage field cost?
Costs vary with the size of the field, ground conditions, excavation requirements and access for machinery and materials. We assess the site and proposed work before preparing a project-specific quotation.
Arrange a drainage field assessment
If your drainage field has failed or you need a new discharge arrangement, CH Services can discuss the ground conditions, the existing system and the next steps. Call 01483 277777 or use the contact form to enquire about drainage field installation in Surrey and West Sussex.