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A treatment plant handles four very different fluids – raw water, potable water, aggressive chemical dosem and abrasive sludge – and each demands a different valve. Specify by media, not by habit, and you avoid contamination, clogging and premature failure. This guide maps valve type and material to each duty.
Potable water → ductile iron with a fusion-bonded epoxy (FBE) internal coating meeting NSF/ANSI 61. The coating keeps iron away from chlorinated water and prevents leaching. Raw water & distribution → same ductile iron + EPDM seat. Chemical dosing (hypochlorite, acid, polymer) → SS316 or PFA/PTFE-lined bodies; PVC/UPVC for non-metallic service. Aggressive / seawater → SS316 or higher. Sludge → knife gate with rubber (EPDM/neoprene) liner.
Residual chlorine (0.2–1.5 mg/L in distribution, up to 5 mg/L at the plant) decides the elastomer. EPDM resists chlorine and is the standard for drinking water. NBR hardens and loses elasticity in chlorinated water – keep it to non-chlorinated wastewater or oil streams. PTFE resists chlorine at any concentration and is used for high-dose chemical lines. SS316 is fine at typical concentrations but can pit above ~200 mg/L, so check the compatibility chart for high-strength disinfection.
Reference AWWA C504 for rubber-seated butterflies, AWWA C509 / C515 for resilient wedge gates, API 609 and EN 593 for butterfly design, and API 598 / ISO 5208 for pressure and seat testing. Every component touching potable water must carry NSF/ANSI 61. Reguvale supplies EPDM-seated ductile-iron butterflies and automated valves built to these specs.
Use a knife gate valve. Its sharp-edged gate slices through sludge and clears solids from the seal, where a standard gate or butterfly would jam. For lightly contaminated effluent a soft-seated butterfly is acceptable, but for primary sludge the knife gate is the reliable choice.
Ductile iron with a fusion-bonded epoxy (FBE) internal coating that meets NSF/ANSI 61. The coating stops iron contact with chlorinated water and prevents leaching. EPDM is the standard seat elastomer for potable water because it resists chlorine at distribution concentrations.
EPDM. It resists chlorine up to 5 mg/L and is the default for drinking water. NBR (nitrile) hardens and loses elasticity in chlorinated water and should be limited to non-chlorinated wastewater or oil-contaminated streams.
AWWA C504 (butterfly), C509/C515 (resilient wedge gate), API 609 and EN 593 (butterfly design), API 598 / ISO 5208 (testing), and NSF/ANSI 61 for any component in contact with potable water.