How Injection Hose Systems Work: Pre-Installed Crack Sealing for Construction Joints

What Is an Injection Hose System?

An injection hose system — also called a pre-installed crack sealing system or kicker hose system — is a method of waterproofing construction joints in below-ground concrete structures before the joint is formed. Rather than attempting to seal a joint after water ingress has been detected, injection hose systems are cast into the concrete during construction, creating a permanent re-injectable conduit along the joint plane. If the joint leaks — immediately after construction or years later — resin can be introduced into the hose from above without excavation, without breaking out the slab and without disrupting the occupied structure.

The technique is widely used in basement construction, underground car parks, service tunnels, swimming pools, water treatment facilities and any below-ground structure where construction joints represent a predictable point of water ingress risk. In the UK, the system is referenced in BS 8102:2022 as a valid component of a Type B (structurally integral) or Type A (barrier) waterproofing strategy when used in combination with other measures, and it is increasingly specified by structural waterproofing designers as a primary joint treatment rather than a remedial fallback.

MPS Concrete Solutions installs injection hose systems as part of new build waterproofing packages and as a proactive measure during planned refurbishment works where wall-slab kicker joints are exposed and re-primed before reinstatement. Our injection hose installation service covers the full scope from design liaison and pre-pour installation through to post-construction activation injection and handover documentation. Full details are available on our Injection Hose Installation service page.

How Injection Hose Systems Are Installed

Installation takes place in two distinct phases: the casting phase, during which the hose is positioned and secured before concrete is placed, and the injection phase, which may occur immediately after striking formwork or — given the re-injectable nature of the system — months or years after the structure is complete.

During the casting phase, the injection hose — typically a corrugated or perforated PVC, rubber or knitted polyester tube with an outer diameter of 10–20 mm — is fixed to the substrate or formwork at intervals of 250–500 mm using nails, staples or adhesive. At kicker joints, the hose is positioned at the centre of the joint width, running continuously along the joint length. At wall-slab joints, the hose is laid on top of the kicker at the point where the next concrete lift will be placed. Hose sections are joined using union connectors, and the ends of each run are extended above the finished concrete surface — or terminated in flush-mounted injection ports — to allow future access for injection equipment.

The hose is kept open and clean during the pour. Concrete is placed and vibrated in the normal manner, though operatives take care not to directly impact the hose with poker vibrators, which can crush or displace it. After concrete is placed and the hose is fully encased, the accessible ends are temporarily sealed with plugs to prevent ingress of laitance and debris during the construction programme. Labels or as-built drawings record the hose layout, terminal positions and the injection port numbering system. This documentation is essential both for the activation injection campaign and for the long-term operation and maintenance manual required under BS 8102:2022.

Types of Injection Hose: Materials and Performance

Three principal hose types are in widespread use on UK commercial projects, each with different permeability characteristics, re-injectability profiles and compatibility with different resin systems. The selection of hose type should be made by the waterproofing designer in consultation with the contractor, taking into account the concrete pour method, the chemical environment and the number of anticipated injection cycles over the design service life.

Corrugated PVC hoses are the most commonly specified type in the UK market. The corrugated outer wall provides a large surface area of fine perforations through which resin can migrate into the joint plane, and the PVC material is compatible with polyurethane, epoxy and acrylate injection resins. Better-quality PVC hoses incorporate a crushable core that collapses under the pressure of fresh concrete but re-opens when injection pressure is applied — a critical performance feature distinguishing them from cheaper tubes that permanently block under pour pressure. PVC hoses are suitable for multiple injection cycles, with the perforations allowing fresh resin to displace degraded or insufficient first-injection material in subsequent campaigns.

Rubber-sheathed hoses offer greater compressive strength and are specified on high-pressure concrete pours where PVC hoses carry a risk of crush. They are also preferred in applications involving aggressive chemical environments — high-sulfate groundwater or chemically contaminated fill, for example — where PVC may degrade over a long service life. The trade-off is typically higher unit cost and reduced availability from UK distributors. Flat injection hoses — made from a non-woven fabric or woven mesh sleeve — are used where section depth is very shallow and a conventional round hose profile would compromise concrete cover to reinforcement. They are particularly suited to floor-slab applications at the junction of a pile cap and a ground-bearing slab.

The Injection Phase: Activating the System After Construction

If water ingress is detected through the joint after construction — or if a proactive injection is specified as part of the commissioning programme — the activation process is straightforward compared with a remedial injection through solid concrete. Injection equipment is connected to the first accessible port on the hose run. Resin — almost always a polyurethane system for joint waterproofing applications, selected for its moisture-cure mechanism and slight expansion on cure — is pumped into the hose at a controlled pressure, typically between 3 and 8 bar. As resin fills the hose, it migrates through the perforations into the joint plane and into any adjacent cracks or voids, where it reacts with moisture and cures to form an elastomeric seal.

Injection continues from port to port along the hose run, monitoring resin bleed at the adjacent port to confirm travel. Where hose runs exceed 5 metres, it is good practice to inject from both ends simultaneously using a Y-connector and twin-pump setup, ensuring the centre of the run receives adequate resin before the perforations seal. Once the full run has been injected and resin has bled from all ports, the ports are sealed and the system is left to cure for a minimum of 24 hours before the joint is subjected to full groundwater pressure.

Because the hose remains permanently within the structure, subsequent injections can be carried out if the first treatment proves insufficient or if new movement reopens the joint at a later date. This re-injectability — not available with conventional hydrophilic strip systems — is the principal commercial argument for injection hose systems on structures with a long design service life or complex groundwater conditions. The additional cost of specifying a hose over a hydrophilic strip at construction stage is typically modest; the saving in remedial access and excavation if the joint later fails can be very substantial indeed.

Injection Hose vs Hydrophilic Strip: Which to Specify?

Hydrophilic waterstop strips — bentonite-based or polyurethane-based profiles fixed to the kicker prior to the next concrete pour — are the most widely used alternative to injection hoses at construction joints in the UK market. They offer simplicity of installation, a single-trade supply-and-fix package, and a well-established track record. Their limitation is that they provide a single sealing opportunity: if the strip is improperly installed, insufficiently hydrated, bridged by laitance or placed in an aggressive chemical environment that inhibits swelling, there is no mechanism for remedial treatment without breaking out the concrete to expose the joint.

Injection hose systems are typically preferred over hydrophilic strips in the following scenarios: structures in aggressive or variable groundwater chemistry, where hydrophilic materials may perform unpredictably; complex or irregular joint geometries where strip continuity is difficult to achieve; structures with a design service life exceeding 50 years, where the re-injectable capability provides measurable risk management value over time; and projects where the waterproofing designer has risk-rated the construction joints as critical and wants a positive remedial route built into the specification from the outset.

A combined approach — hydrophilic strip at the joint face, injection hose at the centreline — is sometimes used on high-risk joints, providing two independent sealing mechanisms and maximising the probability of a dry result even if one system underperforms. This combined specification is common on deep basements in London clay where groundwater heads can reach 10 metres or more and where the consequences of a failed joint are significant in terms of remedial cost and building occupation disruption. For a broader view of below-ground waterproofing strategy, our External Waterproofing and Cavity Drain Installation service pages describe complementary approaches that are frequently used alongside injection hose systems on complex commercial schemes.

Quality Assurance, Documentation and Long-Term Maintenance

A properly documented injection hose installation supports the commissioning, handover and long-term management of a waterproofed structure. As-built drawings should record the hose layout, port positions, hose type and batch reference, date of installation and date of any injection campaigns carried out. This documentation forms part of the building's waterproofing operation and maintenance manual, required under BS 8102:2022 for Grade 2, 3 and 4 below-ground spaces. Without this documentation, future building managers or new owners cannot identify hose terminal locations or understand the remedial route available to them if the joint later shows signs of water ingress.

Maintenance of an injection hose system during the construction programme requires keeping port terminals accessible and protected from damage by follow-on trades. Hose terminals buried under screed or covered by floor finishes before activation injection has been completed — a common cause of system failure on fast-track projects — cannot be accessed without excavation. Coordination between the waterproofing installer, the main contractor and follow-on trades is essential to maintain system integrity from installation through to commission and handover.

If you are specifying a below-ground structure and wish to include injection hose systems as part of the waterproofing strategy, MPS Concrete Solutions can advise on hose type selection, spacing, resin compatibility and quality assurance requirements. We can also survey existing structures where construction joints are the suspected source of water ingress and advise on whether the joint was installed with an accessible hose system and whether remedial injection is viable. Contact our team to arrange a site survey, and review our BS 8102 Compliance Checklist for further guidance on below-ground waterproofing documentation requirements.