Dr. Fixit TankPro W
A two-pack polyurethane membrane built for the inside of a water tank — waterproofing and protection in one coating, certified safe for the drinking water it holds.
What is it?
A two-component, solvent-free, thixotropic elastomeric polyurethane coating that cures into a strong, elastic, hydrophobic membrane.
Where is it used?
Internal surfaces of RCC and precast concrete water tanks, drinking-water reservoirs and other potable-water holding structures.
Why use it?
It’s FDA 175.300 certified for potable water contact, solvent-free so it can be applied inside a closed tank without odour, and elastic enough to bridge live cracks.
How is it applied?
Rolled or trowelled in two coats over a primed, CSP4/5-profiled RCC surface — thin first coat to seal pinholes, second coat perpendicular — totalling 1.4 kg/m².
About Dr. Fixit TankPro W
Waterproofing a water tank isn’t the same problem as waterproofing a terrace. The membrane stays permanently wet, takes hydrostatic pressure from both directions, and — because the water inside ends up in someone’s kitchen tap — has to be genuinely safe for human consumption, not just “waterproof.” Plenty of tank coatings on the market were never actually tested for potable contact. TankPro W was engineered around that specific brief: a two-component elastomeric polyurethane, 100% solids, certified to US FDA 175.300 for drinking-water contact. Being solvent-free, it can be applied inside a closed RCC tank without the ventilation and odour problems solvent-based coatings bring — useful on residential overhead tanks and underground sumps with limited cross-ventilation.
On a real site, TankPro W is rarely used alone — it’s the topcoat of a small system. Dr. Fixit’s own datasheet builds in a primer (Tank Prime), a joint sealant (Feviseal PU/Hybrid), a corner-fillet bonding coat (Pidicrete URP) and a reinforcing tape at the wall-floor junction, because tanks fail at joints and corners long before they fail on the flat wall. Space Arc applies TankPro W as this full system rather than as a standalone tin — the difference between a tank that stays dry for one season and one still leak-free after five monsoons.
The technical insight
The mix ratio is 1 part hardener to 3.84 parts resin by weight — resin-heavy enough that it needs a proper slow-speed paddle mixer, not a stick and bucket. Pot life is just 20 minutes at 25°C and shortens further in Delhi NCR summer heat, so applicators mix small batches and pour into a shallow tray to release trapped air before it goes on the wall — that step is why the first coat comes out pinhole-free. The two-coat regime (0.5 kg/m² then 0.9 kg/m², second coat perpendicular) exists because the coating is thixotropic and won’t self-level over pinholes, so the thin first pass exists specifically to seal them. And the substrate spec — 20 MPa cured concrete, CSP4/5 profile, under 5% moisture — isn’t boilerplate; polyurethane blisters on damp concrete, which is exactly the failure this spec is guarding against.
Where it is used
- Internal lining for RCC overhead and underground water tanks
- Precast and prefabricated concrete tank interiors
- Elevated service reservoirs and municipal drinking-water reservoirs
- New-construction tank lining before first fill
- Rehabilitation of ageing or leaking RCC tanks
- Wall-to-floor and wall-to-wall corner/joint sealing inside tanks
- Crack and construction-joint repair within potable structures
- Protection against hydrolysis and sustained hydrostatic pressure
Key advantages
- FDA 175.300 certified — genuinely fit for drinking water storage
- One coating does waterproofing and protection, cutting site passes
- Solvent-free, 100% solids — safe to apply inside closed tanks
- 100% elongation with 12 MPa tensile strength bridges live movement
- Passes 5 bar hydrostatic pressure, both positive and negative
- Adhesion tests at concrete failure — the bond isn’t the weak point
- Very low 0.15% water absorption limits blistering and delamination
- Passes 10-cycle crack-bridging test for long-term movement tolerance
Limitations & considerations
- Twenty-minute pot life demands disciplined small-batch mixing, especially in summer
- Correct 1:3.84 mixing needs a paddle mixer and trained hands, not a DIY brush job
- Strict surface prep — 20 MPa cured concrete, CSP4/5 profile, under 5% moisture
- Real performance depends on the full primer-sealant-tape system, adding cost and sequencing
- Full cure takes 3–5 days, so fill dates need planning, not last-minute scheduling
- Sold only as a 9 kg kit, which can leave awkward leftovers on small domestic tanks
Selection & best practice
Confirm 28-day cured concrete at 20 MPa minimum and under 5% moisture before priming — polyurethane over damp concrete blisters rather than waterproofs. Apply Tank Prime at 200 gm/m² and let it self-cure before the topcoat, ideally while still tack-free and within 24 hours of priming. Mix Part A into Part B with a slow-speed paddle mixer, decant into a shallow tray to vent trapped air, and batch to the 20-minute pot life rather than mixing a full kit at once in warm weather. Apply the first coat thin at roughly 0.5 kg/m² to seal pinholes, then 0.9 kg/m² perpendicular between 6–24 hours later — re-prime if that window slips. Keep the tank dry through the full cure and for at least 7 hours after the last coat before any water touches the film.
Specifications
| Chemistry | Two-component elastomeric polyurethane, solvent-free |
| Mix Ratio (Hardener : Resin, by weight) | 1 : 3.84 |
| Specific Gravity of mix (ASTM D1475 @25°C) | 1.2–1.3 |
| Pot Life @25°C | 20 minutes |
| Elongation (ASTM D412) | 100% ± 10 |
| Tensile Strength (ASTM D412) | 12 MPa ± 2 |
| Hydrostatic Pressure Resistance (EN 12390 / ASTM D7088) | Passes 5 bar, positive & negative |
| Coverage (two coats) | 1.4 kg/m² total |
| Pack Size | 9 kg kit (~2 kg Part A + ~7 kg Part B) |
Industry use cases
Residential societies
Relining leaking RCC overhead tanks and underground sumps during waterproofing retrofits.
Institutional campuses
New drinking-water storage tanks for schools and hospitals needing potable certification.
Municipal infrastructure
Elevated and ground-level service reservoirs on water-supply projects.
Food & beverage plants
Process and drinking-water tanks needing an FDA-compliant internal lining.
Hospitality
Hotel and resort underground water sumps, where odour-free indoor application matters.
Frequently asked questions
Is TankPro W actually safe for drinking water, or is that just marketing?
How much material does one tank actually need?
How soon can we fill the tank after coating?
Can our own maintenance staff apply this?
What’s the difference between TankPro W and TankPro E?
The coating seems to be changing colour after a few months — is that a defect?
How we position Dr. Fixit TankPro W
Within the Dr. Fixit range, TankPro W pairs with Dr. Fixit Tank Prime as its dedicated primer, Feviseal PU/Hybrid Sealant for crack and joint treatment, and Pidicrete URP for corner-fillet bonding — Space Arc supplies and applies these as one system, not a standalone tin. For tanks holding wastewater or process effluent rather than drinking water, Dr. Fixit TankPro E is the correct sibling, built for chemical and abrasion resistance over potable certification. Outside the Dr. Fixit range, specifiers wanting a rigid, glass-smooth epoxy lining instead of an elastomeric membrane — for tanks with minimal movement, or where an easy-clean hard finish matters more — often look at Fosroc Nitocote EP405, a two-pack 100% solids epoxy system also built for potable water tank linings; Space Arc stocks and applies both and can help decide which chemistry suits a given tank.
Fosroc Nitocote EP405 — Specifiers who prefer a rigid, glass-smooth epoxy lining over an elastomeric polyurethane membrane — for tanks with minimal structural movement or where a hard, easy-clean finish is prioritised — often choose Fosroc Nitocote EP405 instead.
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