Choosing wetted materials, seals, and piping that can handle the chemical, temperature, and pressure they will see. An incompatible material rarely fails straight away. It softens, cracks, or corrodes over weeks, then leaks or ruptures.
Check compatibility for every wetted part before a chemical goes into it. That includes pump heads, tubing, fittings, valve seats, O-rings, sensor bodies, and tanks. The weakest material in the path sets the limit.
A material that suits a chemical at room temperature may not suit it hot, concentrated, or under pressure. Check all three:
Generic compatibility charts are a starting point. They usually assume room temperature and a single chemical, so confirm borderline cases with the supplier.
| Material | Typical use | Watch out for |
|---|---|---|
| Brass and bronze | Pump bodies, valves, fittings | Attacked by acids, hypochlorite and other oxidizers, and ammonia, which can cause stress cracking |
| Stainless steel (304, 316) | Fittings, sensor bodies, injection quills | Pitting from chlorides and hypochlorite; hydrochloric acid attacks it quickly |
| PVC | Chemical feed and low-temperature piping | Limited to about 60 °C (140 °F), with pressure rating falling well before that; brittle in cold and under impact |
| CPVC | Hotter water and chemical lines | Higher temperature limit than PVC, but still derates with heat; some thread sealants and pipe dopes attack it |
| Polyethylene and polypropylene | Tanks, tubing | Degraded by some strong oxidizers and solvents, and by sunlight unless UV-stabilized |
| EPDM | Seals and O-rings in water and glycol | Swells and fails in oils and hydrocarbons |
| FKM (Viton) | Seals for acids and hydrocarbons | Not suited to every chemical; check before assuming it is universal |