Not every industrial pit needs stainless. If the effluent is ordinary mixed sewage and wash-down — not salty, not chemically aggressive — then cast iron is the right, cost-effective build, and paying for stainless is money that could go into a second standby pump instead.
The 100GNWQ100-15-7.5 is that sensible workhorse: 100 m³/h at 15 m head, 7.5 kW, 100 mm outlet, in HT200/HT250 cast iron. It carries the same cutter system as every GNWQ — the 48 HRC alloy disc shredding the rag, wipe and packaging load — and runs a heat-treated 3Cr13 impeller for wear life. You get full anti-clog performance without the stainless premium.
The rule of thumb we give buyers: choose cast iron for ordinary sewage; step up to the SS304 GNWQ-S range only when the fluid is corrosive, salty or food-grade. Not sure which side of that line you’re on? Describe your effluent and we’ll tell you straight — sales@haquanpump.com.