A polyurea water tank lining is one of the few coatings that can do three jobs at once in a drinking-water reservoir. It forms a seamless barrier, it bridges cracks in the concrete, and it can be certified for contact with water intended for human consumption.
The third point is the one that matters most. In potable water, a lining is judged first on hygiene approvals, then on mechanical performance. This article covers both, using data from the Polyurea Rayston and Impermax Aqua 2K technical data sheets (TDS).
What a potable water tank lining has to do
An enclosed reinforced-concrete reservoir has a floor slab, walls, expansion joints, plinths and pipe penetrations. The lining has to stay continuous across all of them.
The engineering requirements are:
- Hygiene: certified for contact with drinking water.
- Watertightness: under constant hydrostatic head.
- Crack bridging: concrete tanks crack with shrinkage and load cycles.
- Chemical resistance: to water, chlorinated water and cleaning agents.
- Continuity: no seams at corners, wall-to-floor junctions or penetrations.
Krypton's engineering note on lining drinking water tanks with polyurea sets out the same list as a design brief.
Certifications for polyurea water tank lining
The Polyurea Rayston TDS lists these approvals relevant to water:
| Approval / test (TDS) | Reference |
|---|---|
| WRAS Material Approval (UK, water for human consumption) | Approval no. 2208579 |
| Drinking water migration test (Applus) | no. 928/09/8505 |
| CE marking, EN 1504-2 | 0370-CPR-2247 |
| European Technical Assessment (ETAG 005) | ETA 16/0148 |
| BBA certificate (UK, roofing) | 18/5582 |
| Environmental Product Declaration | EPD-IES-0020897 |
Always check that the approval covers the exact product and system you are specifying. Krypton's own note makes the point directly: do not conflate the Polyurea Rayston certifications with those of a different product. The UK scheme is run by WRAS / Water Regs UK, where approvals can be checked.
Performance data from the TDS
| Property | Polyurea Rayston |
|---|---|
| Hardness (ISO 868) | 87A / 35D |
| Elongation at break | 324% |
| Tensile strength | 16.2 MPa |
| Tear strength | 69 N/mm |
| Watertightness (EN 12390-8) | Watertight at 5 bar (50 m water column) |
| Liquid water permeability (EN 1062-3) | 0.002 kg/m²·h^0.5 |
| Static crack bridging (EN 1062-7) | Class A5 at -10 °C |
| Adhesion to concrete with epoxy primer | 4.0 MPa |
| Heavy metals (Sb, As, Pb, Cr, Ni, Se, Co) | each below 1 mg/kg |
Immersion resistance
The TDS reports immersion tests on a 0–5 scale (5 = best). Relevant results for water tanks:
- Water, 15 days at 80 °C: 5
- Saturated salt water, 15 days at 80 °C: 5
- Sodium hypochlorite 1%, 7 days at 80 °C: 3
- Bleach, 7 days at 80 °C: 4
These are accelerated tests at 80 °C, which is far more severe than a cold-water reservoir. Use them to compare products, not to predict service life.
Typical system build-up
For enclosed concrete reservoirs, the build-up described in Krypton's tank note is:
- Surface preparation: abrasive blasting or grinding, with defects repaired before spraying.
- Concrete primer: 0.2–0.4 mm, for example Rayston Epoxy 100, or a humidity-tolerant primer where needed.
- Hot-sprayed Polyurea Rayston: 1.8–2 kg/m², around 2 mm nominal thickness.
- No internal aliphatic topcoat. An enclosed tank has no UV exposure, so the polyurea itself is the wet-contact surface.
The fourth point matters. A topcoat inside the tank adds another material to the water-contact surface, and that material would need its own approval.
Cold-applied alternative: Impermax Aqua 2K
Hot-spray rigs are not always practical, for example in small tanks with tight access. The Impermax Aqua 2K TDS describes a solvent-free, two-component polyurethane membrane "certified according to provisions of European regulation 98/83/EC" for contact with drinking water.
| Property | Impermax Aqua 2K |
|---|---|
| Elongation at break | above 130% |
| Tensile strength | 4 MPa |
| Hardness (Shore A) | 66–69 |
| Coat thickness | about 1 mm per 1.5 kg/m² coat |
| Chlorinated water (20 ppm) | 5 (best) |
| Use temperature | -15 °C to 80 °C |
Because it is solvent-free, it suits indoor and poorly ventilated spaces. It is a different product with different approvals, so specify it by name rather than as "equivalent to" the hot-spray polyurea.
Fire water and steel tanks
Not every tank holds drinking water. Fire-water reserves and process tanks need watertightness and corrosion protection, but not necessarily potable approval. See Krypton's pages on fire water tanks and steel tanks and containers. For potable use, start from the drinking-water reservoirs page.
Site QA checklist
- [ ] Approval reference checked against the exact product and system
- [ ] Substrate pull-off at least 1.5 N/mm²; moisture below 4% for standard epoxy primers
- [ ] Primer thickness matched to porosity and moisture
- [ ] Polyurea consumption recorded by weight, plus thickness readings
- [ ] Corners, joints and penetrations detailed and inspected
- [ ] Holiday or visual inspection for pinholes before filling
- [ ] Cure, flushing and disinfection as required by the water authority
Key takeaways
- In a polyurea water tank lining, the hygiene approval comes first: Polyurea Rayston lists WRAS approval 2208579.
- Typical build-up: primer 0.2–0.4 mm, then 1.8–2 kg/m² hot-sprayed polyurea, with no internal topcoat.
- Watertight at 5 bar and Class A5 crack bridging at -10 °C per the TDS.
- Where hot-spray is impractical, Impermax Aqua 2K is the cold-applied, solvent-free option.
FAQ
Is polyurea safe for drinking water tanks?
Only if the specific product is certified for potable contact. Polyurea Rayston lists WRAS material approval and a drinking-water migration test in its TDS. Uncertified polyureas should not be assumed safe.
How thick should a polyurea tank lining be?
Krypton's tank build-up specifies about 2 mm, applied at 1.8–2 kg/m² over a primer.
Does a polyurea tank lining need a topcoat?
Not inside an enclosed tank. There is no UV exposure, and a topcoat would add another material to the water-contact surface.
Can you line a concrete water tank without spray equipment?
Yes, with a cold-applied membrane such as Impermax Aqua 2K, which is certified under 98/83/EC.
Further reading
- Krypton Chemical Solutions: tank and reservoir applications, TDS library and calculator.
- Product catalogue at kryptonchemical.com.
About the author
Krypton Chemical, S.L. Marketing Department, Nidal Malkawi
Krypton Chemical has manufactured construction chemicals in Spain since 1999. Technical resources: kryptonchemicalsolutions.com · Products: kryptonchemical.com
