Dr. Fixit PU Foam Injection
An MDI-based, water-reactive PU grout that chases down active, running-water leaks in concrete and shuts them off within minutes — even against hydrostatic pressure.
What is it?
A single-component, MDI (methylene diphenyl di-isocyanate) based polyurethane injection grout that stays liquid until it contacts water, then reacts and expands 30-40 times its volume into a semi-rigid foam.
Where is it used?
Basements, lift pits and retaining walls, water tanks, tunnels, sewers, manholes, dams and canals — anywhere a crack, cold joint or void is carrying active seepage under pressure.
Why use it?
It is one of the few products that can actually stop water while it is still flowing, rather than needing a dry surface first, which makes it the go-to emergency fix before permanent crack and coating repair.
How is it applied?
Injected through drilled packer ports straddling the crack, using a single- or two-component injection pump, starting from the lowest leak point and working upward until the leak stops and the foam cures.
About Dr. Fixit PU Foam Injection
Dr. Fixit PU Foam Injection is Pidilite’s single-component, MDI-based polyurethane grout, built specifically for the one job ordinary waterproofing coatings can’t do: stopping water that is actively flowing through a crack, construction joint or void while it is still flowing. Pour it into a crack that’s dry and it simply sits there; introduce it to moving water and the resin reacts almost immediately, expanding to 30-40 times its liquid volume as a closed, semi-rigid foam that physically plugs the void from the inside out. That water-triggered reaction is the whole trick, and it’s why site engineers reach for it as the first response on basement leaks, sump pits, tank walls and tunnel linings where the client wants the flow stopped today, not after the monsoon lets up.
It is not, on its own, a finishing product. Because it’s a single-pack, 100% solids, solvent-free system with roughly a 4-hour working pot life at 25°C, it’s built for speed and simplicity on site rather than long open time or elastic long-term crack bridging. Once the active leak is arrested, the crack face still needs proper structural repair — usually a polymer-modified mortar or crack-sealant paste — followed by a compatible surface waterproofing coat to give the client a system that’s actually covered by a workmanship warranty. Treat PU Foam Injection as the emergency valve-shutoff in a larger waterproofing sequence, not the whole job, and it earns its keep on almost every basement and water-retaining structure repair Space Arc gets called to across Delhi NCR.
The technical insight
The chemistry is a hydrophilic MDI pre-polymer plus an accelerator, formulated to stay liquid and inert until it contacts water — then it cross-links and foams, generating the volume expansion that fills irregular crack geometry and honeycombed concrete that a rigid epoxy grout would never reach. This water-reactivity is also its main limitation: cured tensile strength sits around 4-5 N/mm² and shear strength around 0.11 N/mm², both modest next to structural epoxy injection resins, so it is graded for sealing, not for restoring load transfer across a structural crack. For genuinely moving cracks — thermal, expansion-joint or seismic movement — a flexible two-component PU resin with a documented elongation rating is the more durable long-term choice; Dr. Fixit PU Foam Injection is at its best on rigid concrete cracks and cold joints carrying active seepage under hydrostatic head.
Where it is used
- Sealing active, running-water leaks through concrete cracks under hydrostatic pressure
- Basement and retaining-wall leak arrest before structural repair
- Water tank, sump and swimming pool seepage control at cracks and cold joints
- Tunnel, sewer and manhole leak sealing in infrastructure works
- Lift pit and below-ground sump waterproofing under continuous water pressure
- Dam, canal and reservoir joint and crack sealing
- Pipe penetration and utility duct sealing against water ingress
- Emergency/temporary leak arrest ahead of permanent crack and coating repair
Key advantages
- Reacts on contact with water so it actually stops flowing leaks instead of washing away
- Fast-reacting — begins foaming within minutes of hitting water, arresting active seepage quickly
- Expands 30-40x its volume to pack out irregular cracks, cavities and honeycombed concrete
- 100% solids, solvent-free formulation, so there’s no shrinkage from solvent flash-off
- Single-component pack — no on-site mixing ratio to get wrong under time pressure
- Works even under active hydrostatic pressure, making it a genuine emergency-repair option
- Cured foam retains some flexibility, tolerating minor thermal movement at the seal
- Straightforward packer-and-pump injection method that trained applicators can deploy fast
Limitations & considerations
- Primarily a fast leak-arrest measure — for actively moving structural cracks a flexible two-component PU or epoxy resin is the more durable long-term fix
- Cured tensile (4-5 N/mm²) and shear (0.11 N/mm²) strength are modest next to structural epoxy grouts, so it isn’t meant for load-bearing crack bonding
- Needs proper injection equipment (packers, pump) and a trained applicator — not a brush-and-pour DIY product
- Roughly 4-hour pot life at 25°C means prepared material has a limited working window on hot Delhi NCR summer days
- Result depends heavily on correct packer placement, spacing and injection sequence, not just the material
- Must be followed by crack-face structural repair and a topical waterproofing coat for a complete, warrantable system
Selection & best practice
Drill packer holes on either side of the crack at roughly 45 degrees so they intersect it mid-depth, spacing them 150-300 mm apart depending on crack width, and start injecting from the lowest point of the leak, working upward so the foam displaces water ahead of it instead of trapping it behind. Keep a second person watching the crack line on the reverse face (or the lift pit below) to confirm the foam is tracking along the crack rather than just building pressure at one packer. Because pot life is short at higher site temperatures, mix and prepare only what one packer run will use, and don’t pull packers until the foam has fully cured and gone rigid — removing them early lets residual water pressure push the plug back out before it sets. Once the leak is confirmed dry, cut back and repair the crack face with a cementitious or epoxy crack filler, then run a compatible Dr. Fixit topical waterproofing coat over the repaired zone — the injection alone was never meant to be the finish.
Specifications
| Chemistry / base | MDI (methylene diphenyl di-isocyanate) pre-polymer with accelerator, single-component |
| Form | 100% solids, solvent-free liquid; foams into semi-rigid closed-cell PU on contact with water |
| Pot life | Approx. 4 hours at 25°C |
| Maximum expansion | Up to 30-40 times original liquid volume in presence of water |
| Tensile strength | 4-5 N/mm² |
| Shear strength | 0.11 N/mm² |
| Relative elongation | 10-20% |
| Application temperature range | 5°C to 40°C |
| Pack size | 5.5 kg (also available in 20 kg) |
Industry use cases
Residential basements & podiums
Arresting active seepage through construction joints and shrinkage cracks in basement walls before the crack repair and waterproof coating stage.
Water & wastewater infrastructure
Sealing running leaks in RCC water tanks, sumps, STP/ETP chambers and manholes where the structure can’t be taken fully out of service.
Tunnels & metro/underground works
Stopping segmental joint and crack seepage in tunnel linings and underground stations under continuous groundwater pressure.
Industrial & warehouse facilities
Sealing lift pits, cable trenches and retaining walls in NCR industrial sheds where standing groundwater causes recurring seepage.
Dams, canals & reservoirs
Emergency sealing of construction joints and cracks in hydraulic structures ahead of a full joint-repair programme.
Frequently asked questions
Can this actually stop water that is still flowing, or does the crack need to be dry first?
Is Dr. Fixit PU Foam Injection the same as Dr. Fixit Crack-X Shrinkfree?
Is this a DIY product a homeowner can apply?
How is this different from an epoxy injection resin?
Will the seal last permanently, or is it a temporary fix?
How much do I need for a typical basement crack?
How we position Dr. Fixit PU Foam Injection
Within the Dr. Fixit range this product sits upstream of the finishing systems: use it to kill an active leak first, then hand off to Dr. Fixit Crack-X Shrinkfree for the crack-face repair and to Dr. Fixit Pidiproof LW+ or Dr. Fixit Pidicrete URP for the structural or topical waterproofing that follows. It is not a substitute for either — it buys the dry, workable surface those systems need. Specifiers who need a two-component resin with a documented elongation spec for genuinely moving cracks, or who are already running a Fosroc injection programme on a project, typically look at Fosroc Nitofill PU12F, a single-component, water-reactive PU resin built for the identical active-leak scenario; where the crack is confirmed non-moving and higher chemical resistance is wanted, Fosroc’s two-component Nitofill PU23/PU25LV resins are the step up. Space Arc stocks and applies both brands, so the choice comes down to the specific crack behaviour and the spec on the drawing, not brand availability.
Fosroc Nitofill PU12F — A specifier already standardised on Fosroc, or one needing a single-component water-reactive PU resin with Fosroc’s documented injection-system backing, would choose Nitofill PU12F for the same active-leak scenario Dr. Fixit PU Foam Injection targets.
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