A fire water tank is the one piece of infrastructure nobody thanks until the sprinkler runs dry. Yet many EPC bids treat it as "a water tank with red paint." Zhongneng Huajian's 600 m³ Zhejiang tannery fire tank (20-day install) and 2,000 m³ Jilin thermal power heat-water tank show the range; the engineering logic below is generic.
Step 1: Capacity, not guesswork
NFPA 22 (US) and GB 50974 (China) both size from sprinkler design flow + hose stream + duration. A medium chemical workshop at 30 L/s sprinkler + 20 L/s hose for 2 h = (50 L/s × 7200 s) = 360 m³, plus 10 % margin and dead-volume below suction = order 400–500 m³, not 300. Buyers who skip the hydraulic calculation end up with a tank that passes visual but fails fire bureau mock drill.
Step 2: Lining choice
Municipal water, pH 6.5–8.5 → carbon steel + pure epoxy (two coats, 240 µm).
High chloride groundwater seepage risk → epoxy coal tar or glass flake.
Pharma/food plant → 304 stainless, thinner wall, no lining needed.
Never use bare carbon steel for fire water in coastal humidity-internal rust flakes clog fire pump strainer in year 3.
Step 3: Nozzle geometry
Suction nozzle must be at least 150 mm above tank bottom to clear sediment, but below low-level alarm. Overflow pipe diameter ≥ inlet diameter + 1 size, discharged to safe drain, not onto electrical trench. Roof vent with insect screen, manhole 600 mm minimum for entry.
Three common rejection reasons at FAT
Coating DFT short by 20 µm because inspector did not check dew-point margin-repaint whole course.
Suction elbow too close to bottom sump → turbulent vortex at pump start → hydraulic report fails.
Level switch threads not food/water graded → algae grows on nylon nut.
FAQ snippet
"Do fire water tanks need to be insulated?" Only if freeze risk: north China, Central Asia, high plateau. ZN's Jilin 2,000 m³ hot-water tank used 100 mm PU + aluminum cladding; a cold fire-water tank uses 50 mm mineral wool and heat-trace.
Specify the tank as a fire-system component, not a water container, and the supplier's questions (flow? duration? freeze? third-party fire engineer?) will tell you whether they understand the job.
