Water & Wastewater Gaskets
Chloramine-resistant elastomers and AS/NZS 4020 compliant gaskets for potable water, treatment plants, and distribution networks.
Australia's shift to chloramine disinfection changed the rules for water infrastructure sealing. Sulphur-cured EPDM — once the default — degrades within 12–18 months in chloraminated systems. We supply peroxide-cured EPDM and specialist elastomers matched to each stage of the water treatment cycle.
Sealing at Every Stage of Treatment
Water treatment follows a predictable cycle — and each stage puts different demands on seals and gaskets.
Raw Water Intake
Screen and pump stations pulling from reservoirs, rivers, or bores. Large-diameter full-face EPDM gaskets on AS 4087 and AS 2129 flanges, butterfly valve seals, and expansion joints absorbing ground movement and thermal cycling.
Typical: DN 300–1200 | PN 16 | EPDM, rubber-lined steel
Treatment and Filtration
Clarifiers, sand filters, membrane skids, UV reactor chambers, and ozone advanced-water-treatment trains. Gaskets here see flocculation chemicals (alum, polyelectrolytes), backwash surges, and varying pH. PTFE-faced gaskets on chemical injection flanges prevent media attack. Ozone callout: peroxide-cured EPDM degrades under continuous ozone exposure. Specify PTFE or FKM for ozone contactor flanges and off-gas piping (SA Water Adelaide Desal, Sydney Water Quakers Hill AWT).
Typical: DN 50–600 | PN 16–21 | EPDM, PTFE, FKM (ozone)
Disinfection
Chlorine gas, sodium hypochlorite, or chloramine dosing — the stage that breaks conventional gaskets. NaOCl degrades at temperatures above 35 °C, producing aggressive by-products. PTFE seals on NaOCl dosing lines, FKM for ferric chloride, peroxide-cured EPDM downstream.
Typical: DN 15–100 | PN 16 | FKM, peroxide-cured EPDM, PTFE
Distribution Network
Trunk mains, service reservoirs, pressure-reducing valves, metering stations, and dual-reticulation recycled-water (purple-pipe) networks. Gaskets live underground for 25–50 years with no maintenance access. Peroxide-cured EPDM is non-negotiable here; sulphur-cured grades cannot survive long-term chloramine exposure. For Class A+ recycled water services — Western Corridor, Bundamba, Luggage Point, and Eastern Treatment Plant — both AS/NZS 4020 and the Australian Guidelines for Water Recycling (AGWR) apply. Potable-water specifications remain in force alongside these.
Typical: DN 100–900 | PN 16 | Peroxide-cured EPDM, AS/NZS 4020 grades (potable + Class A+)
Wastewater Collection
Sewer mains, pump stations, and rising mains carrying raw sewage with fats, oils, greases, and grit. Seals need chemical resistance to H₂S (up to 200 ppm in headspace) and abrasion resistance from entrained solids. NBR suits oil-contaminated flows; EPDM elsewhere.
Typical: DN 150–1200 | PN 10–16 | EPDM, NBR
Biogas and Resource Recovery
Digesters, gas holders, and cogeneration engines producing biogas (60% CH₄, 40% CO₂, 200–5,000 ppm H₂S). Gaskets on digester covers, gas mixing systems, and engine exhaust connections need FKM or PTFE to resist H₂S and condensate at elevated temperatures.
Typical: DN 100–600 | PN 10–16 | FKM, PTFE, spiral wound 316L
The Chloramine Problem
Most Australian water utilities have switched from free chlorine to chloramine (monochloramine) for residual disinfection. Chloramine is more stable across long distribution networks — but it attacks sulphur-cured EPDM from the inside out.
The sulphur cross-links that give conventional EPDM its elasticity become the point of chemical attack. Within 12–18 months, gaskets swell, soften, and lose compression set. Flanged joints that passed hydrostatic testing at commissioning develop weeping leaks that are expensive to fix on buried infrastructure.
Peroxide-cured EPDM uses carbon-carbon cross-links instead — chemically inert to chloramine. We run extended chloramine immersion testing to 1,000 hours — well beyond the 7-day ASTM D6284 standard. Peroxide-cured grades retain more than 90% of tensile strength. Sulphur-cured grades can lose 40–60% in the same test.
Sulphur vs. Peroxide Cure
You cannot distinguish sulphur-cured from peroxide-cured EPDM by appearance. Both are black, both have similar hardness. The only reliable indicator is the material certificate from the compounder. If your gasket supplier cannot confirm the cure system, assume sulphur-cured and replace before connecting to a chloraminated supply.
We supply peroxide-cured EPDM with batch traceability to the compound. Ask for our chloramine-grade material data sheets.
Conventional vs. Recommended Practice
Standards and Certifications
Water industry gaskets sit at the intersection of public health regulation and infrastructure engineering standards. We can advise on which standards apply to your specific installation.
AS/NZS 4020:2018 (Amd 1:2022)
Products in contact with drinking water. Tests for taste, odour, appearance, cytotoxicity, mutagenicity, and metals extraction. Amendment 1 (September 2022) added NDMA (N-nitrosodimethylamine) leachate testing in monochloramine water with a 30 ng/L limit, directly relevant to networks that disinfect with chloramine. Mandatory for all potable water contact materials.
WaterMark Certification
ABCB WaterMark scheme for plumbing and drainage products. Increasingly required by water authorities for gaskets in regulated infrastructure. Third-party audited manufacturing and material compliance.
AS/NZS 4087:2011
Metallic flanges for waterworks purposes. Current standard for Australian water infrastructure. Pressure classes PN 16, PN 21, PN 35. Figure B5/B6 gasket dimensions for full-face and ring configurations.
WSA 109:2021
Water industry standard for flange gaskets and O-rings. Defines material requirements and joining guidelines for flanged connections in water supply and sewerage pipelines.
AS 1646:2007
Elastomeric seals for waterworks purposes. Specifies rubber compound requirements including hardness, tensile strength, elongation, and compression set for water industry sealing applications.
ASTM D6284
Standard test for rubber property resistance to aqueous chloramine. The benchmark for comparing peroxide-cured vs. sulphur-cured EPDM. Standard 7-day (168-hour) immersion protocol; extended durations (1,000+ hours) used for comparative evaluation.
AS 2129:2000
Flanges for pipes, valves, and fittings (Table flanges). Common in pre-2000 water infrastructure. Still encountered extensively during maintenance and upgrades of ageing distribution networks.
AS/NZS 3500
National plumbing and drainage code. Specifies requirements for water services, sanitary plumbing, stormwater drainage, and heated water systems. Gasket materials in potable systems must comply with AS/NZS 4020.
Materials for Water Infrastructure
Primary choice for chloraminated water systems. Carbon-carbon cross-links resist chloramine attack. -50 °C to +150 °C. AS/NZS 4020 grades available.
For ferric chloride, polymer dosing, and non-oxidising chemical lines. -20 °C to +205 °C. Not recommended for NaOCl; use PTFE or EPDM for hypochlorite service.
Near-universal chemical resistance for ozone systems, peroxide dosing, and high-purity water. Envelope gaskets for chemical injection flanges. AS/NZS 4020 grades available.
Cost-effective for non-critical utility service (pump flanges, air system connections, non-potable water). Klingersil C-4400 suits general waterworks duty.
High-pressure desalination service — reverse osmosis skids and HP pump connections. Super duplex windings available for seawater intake and brine reject lines.
Niche use for oil-contaminated wastewater and trade waste applications. Good fuel and grease resistance. -40 °C to +120 °C. Not suitable for potable water service.
Products for Water and Wastewater
Engineering Guides for Water Infrastructure
We maintain technical guides and reference tools to help you select the right material and gasket type for water and wastewater applications.
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Need Gaskets for Water Infrastructure?
Our team can help you select the right elastomers and gasket types for your specific water or wastewater application, from chloramine-grade EPDM for distribution mains to FKM seals for chemical dosing systems.
- Peroxide-cured EPDM with batch traceability
- AS/NZS 4020 test certificates supplied on request
- Consolidated supply across AS 4087, AS 2129, and BS 10 flanges
Disclaimer
This page is provided for general engineering reference only and does not constitute professional advice, specification, or guarantee of performance. Actual results depend on specific application conditions. Universal Gaskets Pty Ltd accepts no responsibility or liability for decisions made based on this information. For full terms, see our Terms & Conditions.
Temperature ranges, chemical resistance ratings, and mechanical properties cited on this page are typical values for standard grades. Actual performance varies with compound formulation, filler package, and service conditions — contact us to confirm suitability for your specific application.