Speedy UK Deliveries
100% SECURE PAYMENT
VOLUME DISCOUNTS
Contact us
Speedy UK Deliveries100% SECURE PAYMENTVOLUME DISCOUNTSContact us
A soakaway can have the correct crate volume and still fail early if fine soil is allowed into the system. A properly specified geotextile membrane soakaway keeps surrounding ground separate from the voids that store and disperse rainwater. It is a relatively modest part of the installation, but it has a direct effect on long-term drainage performance.
For builders, groundworkers and capable DIY installers, the key point is simple: use a permeable geotextile around the soakaway system, install it without gaps, and size the whole arrangement around the site’s actual ground conditions. The membrane does not make unsuitable ground drain better, and it does not replace proper testing, pipework falls or accessible maintenance points.
A soakaway collects surface water from roofs, channel drainage or hard landscaping, holds it temporarily within crates or granular fill, then allows it to infiltrate surrounding soil. The membrane forms a filter layer between the stored water and that soil.
Its main job is to allow water through while retaining fine particles. Without that separation, silt and soil can migrate into crate openings or aggregate voids. Over time, this reduces storage capacity and can restrict the rate at which water moves through the system. The visible result may be standing water by a patio, overflowing gullies or water backing up towards the building during heavy rainfall.
A geotextile also separates different construction layers. This is particularly useful where a soakaway sits in fine clayey soil, silty ground or made-up ground that is prone to movement when wet. It helps keep the drainage medium and the native soil in their intended places.
Do not confuse a geotextile with an impermeable geomembrane. A geomembrane is used where water must be contained, such as a lined attenuation tank or pond. Wrapping a conventional infiltration soakaway in an impermeable liner would prevent water reaching the surrounding ground, which defeats its purpose.
For most crate-based soakaways and aggregate-filled pits, a non-woven, needle-punched geotextile is the usual choice. It is permeable, flexible and suited to filtration and separation duties. The material should be specified for drainage use rather than selected solely because it is labelled as a general weed-control fabric.
The correct grade depends on the ground, installation depth, loading and the drainage design. A membrane needs adequate puncture resistance to withstand handling, excavation conditions and contact with angular stone. It also needs suitable filtration characteristics for the soil it will sit against. Very fine soils can require more careful material selection because a membrane that is too open may allow fines to pass, while one that is too restrictive can reduce flow at the interface.
For domestic work, it is tempting to choose the heaviest membrane available. More weight is not automatically better. A heavier material may offer useful protection, but drainage performance, filtration opening size and compatibility with the system matter as much as thickness. For commercial yards, trafficked areas or deeper excavations, follow the drainage designer’s specification and the crate manufacturer’s installation requirements.
Where modular soakaway crates are being used, check whether the manufacturer requires a particular membrane grade or overlap detail. Load-bearing crates, crate connectors, side panels and geotextile all work as part of one installation. Mixing components without checking compatibility can create weak points or affect warranty conditions.
Soakaway sizing should be based on the drainage area, local rainfall allowance and the ability of the soil to accept water. The usual starting point is an infiltration test carried out at the proposed depth, with the results used in the drainage design. This is especially important on clay, dense subsoil, sites with a high water table or plots where ground has been disturbed by previous construction.
A fast-draining sandy soil may accept a compact soakaway. Slow-draining ground may require a much larger system, an alternative surface-water strategy or a designed attenuation arrangement with controlled discharge where permitted. Simply adding more crates to poorly draining clay does not solve the underlying issue.
Location matters just as much. A soakaway should be positioned clear of buildings, boundaries, foundations and services in accordance with the project design and applicable Building Regulations guidance. Avoid placing it where concentrated water could affect neighbouring land, destabilise a retaining structure or saturate an existing driveway sub-base. Always identify buried utilities before excavation.
For extensions and new-build work, drainage proposals may need Building Control approval. A competent drainage designer can account for roof area, finished levels, pipe capacity, groundwater, soil permeability and future maintenance access. That early planning is normally less expensive than reopening a landscaped garden after a failed installation.
Excavate the soakaway pit to the required dimensions, allowing enough room for the membrane to line the base and sides and to fold over the completed system. Remove loose spoil, sharp projections and large stones that could damage the fabric. If the excavation base is soft or uneven, address this before crates or aggregate are placed.
Lay the geotextile across the base and up each side in one continuous arrangement where practical. Avoid stretching it tight. A little slack allows the fabric to sit into corners and around the system without tearing as the installation is loaded and backfilled.
If more than one sheet is needed, overlap the joints generously. The required overlap can vary with the material, ground type and manufacturer guidance, but the aim is consistent: no open route for soil to enter the soakaway. Keep overlaps facing so that backfill does not pull them apart, and avoid unnecessary cuts. Where a pipe enters the system, make a neat, close-fitting opening and seal or fold the membrane detail as specified by the crate supplier.
With crate systems, assemble the modules on the lined base, using the required clips, connectors and side panels. Connect the incoming drainage pipework with the correct adaptors and maintain the designed fall. A rodding or inspection point may be appropriate on the pipe run, particularly where leaves, roof debris or channel drainage silt could collect upstream.
Once the system is complete, fold the membrane over the top so the crates or clean stone are fully enclosed. Check that every side, joint and penetration remains protected before backfilling. Do not drag heavy spoil across exposed fabric, and do not allow sharp rubble, broken brick or contaminated fill to sit directly against it.
Backfill in controlled layers using suitable material for the loading above. The required cover depth and backfill specification depend on whether the area will be landscaped, paved or subject to vehicle loading. A domestic lawn installation and a driveway receiving regular vehicle traffic are not equivalent applications. Where a soakaway is beneath a drive, both the crate system and the construction above it must be designed for that loading.
The most frequent failure is leaving part of the system unwrapped. This often happens when the membrane is cut too small, pulled tight around a crate, or folded over before pipe connections are complete. A small exposed area can become a route for fines over years of wet weather.
Another mistake is using an impermeable sheet because it appears tougher or more waterproof. For an infiltration system, water must pass through the wrap. The requirement is filtration, not containment.
Poor upstream drainage control also causes problems. Gutters need leaf protection where appropriate, gullies need to be kept clear and channel drains need regular cleaning. A membrane reduces migration of surrounding soil, but it cannot compensate for roof moss, gravel, silt and debris entering from above.
Finally, do not treat every excavation as suitable for a soakaway. If the test results, groundwater conditions or site layout indicate that infiltration is unsuitable, select a drainage solution designed for the restrictions rather than forcing a crate system into the ground.
A soakaway installation is easier to complete when the connected items are planned together: underground drainage pipe, bends, junctions, gullies or channel outlets, inspection access, crates, connectors and the correct geotextile. Matching the pipe diameter and fittings before excavation reduces site delays and improvised connections.
Speedy Plastics supplies trade-ready drainage and water-management products for domestic, commercial and agricultural applications, with competitive VAT-inclusive pricing and fast UK delivery options. For larger projects, confirm quantities, crate specification and membrane coverage before ordering so the system can be installed as designed.
A correctly wrapped soakaway is largely out of sight once the ground is reinstated, which is precisely why careful material choice and tidy installation are worth getting right first time.
A soakaway can have the correct crate volume and still fail early if fine soil is allowed into the system. A properly specified geotextile membrane soakaway keeps surrounding ground separate from the voids that store and disperse rainwater. It is a relatively modest part of the installation, but it has a direct effect on long-term drainage performance.
For builders, groundworkers and capable DIY installers, the key point is simple: use a permeable geotextile around the soakaway system, install it without gaps, and size the whole arrangement around the site’s actual ground conditions. The membrane does not make unsuitable ground drain better, and it does not replace proper testing, pipework falls or accessible maintenance points.
A soakaway collects surface water from roofs, channel drainage or hard landscaping, holds it temporarily within crates or granular fill, then allows it to infiltrate surrounding soil. The membrane forms a filter layer between the stored water and that soil.
Its main job is to allow water through while retaining fine particles. Without that separation, silt and soil can migrate into crate openings or aggregate voids. Over time, this reduces storage capacity and can restrict the rate at which water moves through the system. The visible result may be standing water by a patio, overflowing gullies or water backing up towards the building during heavy rainfall.
A geotextile also separates different construction layers. This is particularly useful where a soakaway sits in fine clayey soil, silty ground or made-up ground that is prone to movement when wet. It helps keep the drainage medium and the native soil in their intended places.
Do not confuse a geotextile with an impermeable geomembrane. A geomembrane is used where water must be contained, such as a lined attenuation tank or pond. Wrapping a conventional infiltration soakaway in an impermeable liner would prevent water reaching the surrounding ground, which defeats its purpose.
For most crate-based soakaways and aggregate-filled pits, a non-woven, needle-punched geotextile is the usual choice. It is permeable, flexible and suited to filtration and separation duties. The material should be specified for drainage use rather than selected solely because it is labelled as a general weed-control fabric.
The correct grade depends on the ground, installation depth, loading and the drainage design. A membrane needs adequate puncture resistance to withstand handling, excavation conditions and contact with angular stone. It also needs suitable filtration characteristics for the soil it will sit against. Very fine soils can require more careful material selection because a membrane that is too open may allow fines to pass, while one that is too restrictive can reduce flow at the interface.
For domestic work, it is tempting to choose the heaviest membrane available. More weight is not automatically better. A heavier material may offer useful protection, but drainage performance, filtration opening size and compatibility with the system matter as much as thickness. For commercial yards, trafficked areas or deeper excavations, follow the drainage designer’s specification and the crate manufacturer’s installation requirements.
Where modular soakaway crates are being used, check whether the manufacturer requires a particular membrane grade or overlap detail. Load-bearing crates, crate connectors, side panels and geotextile all work as part of one installation. Mixing components without checking compatibility can create weak points or affect warranty conditions.
Soakaway sizing should be based on the drainage area, local rainfall allowance and the ability of the soil to accept water. The usual starting point is an infiltration test carried out at the proposed depth, with the results used in the drainage design. This is especially important on clay, dense subsoil, sites with a high water table or plots where ground has been disturbed by previous construction.
A fast-draining sandy soil may accept a compact soakaway. Slow-draining ground may require a much larger system, an alternative surface-water strategy or a designed attenuation arrangement with controlled discharge where permitted. Simply adding more crates to poorly draining clay does not solve the underlying issue.
Location matters just as much. A soakaway should be positioned clear of buildings, boundaries, foundations and services in accordance with the project design and applicable Building Regulations guidance. Avoid placing it where concentrated water could affect neighbouring land, destabilise a retaining structure or saturate an existing driveway sub-base. Always identify buried utilities before excavation.
For extensions and new-build work, drainage proposals may need Building Control approval. A competent drainage designer can account for roof area, finished levels, pipe capacity, groundwater, soil permeability and future maintenance access. That early planning is normally less expensive than reopening a landscaped garden after a failed installation.
Excavate the soakaway pit to the required dimensions, allowing enough room for the membrane to line the base and sides and to fold over the completed system. Remove loose spoil, sharp projections and large stones that could damage the fabric. If the excavation base is soft or uneven, address this before crates or aggregate are placed.
Lay the geotextile across the base and up each side in one continuous arrangement where practical. Avoid stretching it tight. A little slack allows the fabric to sit into corners and around the system without tearing as the installation is loaded and backfilled.
If more than one sheet is needed, overlap the joints generously. The required overlap can vary with the material, ground type and manufacturer guidance, but the aim is consistent: no open route for soil to enter the soakaway. Keep overlaps facing so that backfill does not pull them apart, and avoid unnecessary cuts. Where a pipe enters the system, make a neat, close-fitting opening and seal or fold the membrane detail as specified by the crate supplier.
With crate systems, assemble the modules on the lined base, using the required clips, connectors and side panels. Connect the incoming drainage pipework with the correct adaptors and maintain the designed fall. A rodding or inspection point may be appropriate on the pipe run, particularly where leaves, roof debris or channel drainage silt could collect upstream.
Once the system is complete, fold the membrane over the top so the crates or clean stone are fully enclosed. Check that every side, joint and penetration remains protected before backfilling. Do not drag heavy spoil across exposed fabric, and do not allow sharp rubble, broken brick or contaminated fill to sit directly against it.
Backfill in controlled layers using suitable material for the loading above. The required cover depth and backfill specification depend on whether the area will be landscaped, paved or subject to vehicle loading. A domestic lawn installation and a driveway receiving regular vehicle traffic are not equivalent applications. Where a soakaway is beneath a drive, both the crate system and the construction above it must be designed for that loading.
The most frequent failure is leaving part of the system unwrapped. This often happens when the membrane is cut too small, pulled tight around a crate, or folded over before pipe connections are complete. A small exposed area can become a route for fines over years of wet weather.
Another mistake is using an impermeable sheet because it appears tougher or more waterproof. For an infiltration system, water must pass through the wrap. The requirement is filtration, not containment.
Poor upstream drainage control also causes problems. Gutters need leaf protection where appropriate, gullies need to be kept clear and channel drains need regular cleaning. A membrane reduces migration of surrounding soil, but it cannot compensate for roof moss, gravel, silt and debris entering from above.
Finally, do not treat every excavation as suitable for a soakaway. If the test results, groundwater conditions or site layout indicate that infiltration is unsuitable, select a drainage solution designed for the restrictions rather than forcing a crate system into the ground.
A soakaway installation is easier to complete when the connected items are planned together: underground drainage pipe, bends, junctions, gullies or channel outlets, inspection access, crates, connectors and the correct geotextile. Matching the pipe diameter and fittings before excavation reduces site delays and improvised connections.
Speedy Plastics supplies trade-ready drainage and water-management products for domestic, commercial and agricultural applications, with competitive VAT-inclusive pricing and fast UK delivery options. For larger projects, confirm quantities, crate specification and membrane coverage before ordering so the system can be installed as designed.
A correctly wrapped soakaway is largely out of sight once the ground is reinstated, which is precisely why careful material choice and tidy installation are worth getting right first time.
