GFS Water Tanks: One Coating, Four Very Different Duties

A glass fused to steel tank for potable water and one for raw water may look identical on the drawing, use the same plates and the same bolts, and still be wrong for each other's duty. The coating is the same. Everything that determines whether the tank actually does its job is different: the certification for the stored water, the inlet and outlet arrangement that controls turnover, the roof and venting that control what gets in, and the accessories that maintain water quality rather than merely holding it.

Shijiazhuang Zhengzhong Technology Co., Ltd. (Center Enamel) supplies GFS tanks for potable, raw, fire and reclaimed water, and the four duties are specified differently even though the shell and coating are the same product.

The tank itself: steel plates with a vitreous enamel coating fused at roughly 820-930 degrees Celsius to a thickness of 0.25-0.45 mm, holiday tested at 1500 V, with adhesion around 3450 N/cm2 and hardness about 6.0 Mohs; bolted with 8.8 grade fasteners and designed structurally to AWWA D103-09 or the applicable local code. That combination gives an inert, smooth, non-leaching surface that does not need periodic re-lining and tolerates cleaning. Because the coating is fused rather than applied, it cannot undercut, and because the plates are finished in the factory there is no site lining and no field welding through the coating.

• Fused Coating: 0.25-0.45 mm fused at 820-930 degrees Celsius - inert, smooth and non-leaching, with no periodic re-lining cycle.
• Verified Quality: 1500 V holiday test over the full surface, adhesion about 3450 N/cm2, hardness about 6.0 Mohs, recorded per plate.
• Bolted Assembly: Factory-finished plates with 8.8 grade fasteners; no site welding and no field lining.
• Structural Code: Designed to AWWA D103-09 or the local equivalent, against stated wind, snow and seismic values.
• Long Service Life: Commonly designed for 30 years or more, with maintenance limited to inspection rather than re-coating.

Potable storage is a water quality problem, not a containment problem. The coating in contact with drinking water must carry a health-effects certification - NSF/ANSI 61, WRAS or the national equivalent - and that certification covers what may leach into the water, not the coating's corrosion resistance or structural performance. Beyond certification, potable tanks need hydraulic design that protects quality: inlet and outlet placed to avoid short-circuiting, a turnover rate that keeps disinfectant residual alive, a screened and vermin-proof vent and overflow, a roof that excludes light and debris, and provision for cleaning and disinfection. Water that sits too long loses residual and grows biofilm; water that short-circuits does the same even when the tank is nominally full.

• Certification Is Mandatory: NSF/ANSI 61, WRAS or national equivalent, with the scope checked. It covers health effects, not corrosion resistance.
• Turnover and Residual: Storage time drives disinfectant decay. Size for the turnover the water quality requires, not only for the volume the network needs.
• Avoid Short-Circuiting: Inlet and outlet placement is the cheapest water quality measure available; put them apart and at different levels.
• Exclude Light and Debris: A covered, screened and vermin-proof tank prevents algae and contamination - the two most common quality complaints.
• Cleaning and Disinfection: Access, drain and disinfection provisions should be designed in, because every potable tank is cleaned eventually.

Fire storage is a guarantee of availability: usable volume rather than nominal volume, a dedicated suction arrangement under the applicable fire code, low-level alarm, refill capacity sized to restore the reserve within the required period, and freeze protection where it is needed. It is the only one of the four duties where the water is never meant to move until an emergency, which is why level indication and anti-vortex provisions matter more than hydraulics. Raw water storage is the opposite: the water is deliberately untreated, so the priorities are excluding light to suppress algal growth, managing sediment load from the source, and providing for desilting. Reclaimed or reclaimed-quality water sits between the two and usually brings its own signage, cross-connection control and sometimes colour-coding requirements.

• Fire - Usable Volume: State usable volume, set the suction elevation deliberately, fit anti-vortex and screen, and provide low-level alarm.
• Fire - Dedication and Refill: Permanent dedicated suction arrangement and refill capacity sized to the required restoration period.
• Raw - Exclude Light: An opaque roof suppresses algal growth. This is the single most effective raw water quality measure.
• Raw - Manage Sediment: Source water carries silt; provide for desilting and account for the sediment volume in the effective capacity.
• Reclaimed - Control and Marking: Cross-connection control, identification and signage per local rules, and often a distinct colour scheme.

Every tank delivered by Shijiazhuang Zhengzhong Technology Co., Ltd. (Center Enamel) is engineered against AWWA D103-09 and EN 1090 with finite element verification of shell, roof and nozzle loads, fused at 820-930°C under ISO 9001 and ISO 45001 control, holiday tested at 1500 V across one hundred percent of the surface, and assembled with Grade 8.8 bolts and manufacturer-certified sealant. GFS water tanks are supplied with coating certified for the stored water where required, hydraulic arrangements reviewed for turnover and short-circuiting, roof and venting provisions matched to the duty, accessories sized for the actual fill and draw rates, and a documentation package that includes the coating test records.

The coating is the same in all four duties. The duty is defined by the certification, the hydraulics and the accessories - which is why a water tank specification should never stop at the shell.

The shell and coating can be, but combining the duties on one tank creates a conflict: fire storage must remain full and dedicated, while potable storage is drawn down and refilled daily. Codes generally require the fire reserve to be protected against use for other purposes. Where a combined tank is proposed, the fire portion must be secured by a permanent arrangement such as a standpipe, and the authority having jurisdiction should confirm acceptance.

No. NSF/ANSI 61 is a health-effects standard: it addresses what may leach from the material into drinking water. It says nothing about resistance to a specific chemical, temperature or concentration. For non-potable or aggressive liquids, compatibility must be assessed separately and in writing, whatever the certification says.

Inspection intervals are set by local regulation and the operator's risk assessment, with annual external inspection and periodic internal inspection and cleaning common. What matters is that the intervals are written down at handover, that sediment depth and coating condition are recorded each time, and that disinfection is carried out and verified after any internal entry.

Yes. Volume and geometry, coating grade and certification for the stored water, roof type and venting, inlet and outlet arrangement and levels, nozzles and appurtenances, level indication and alarms, insulation and freeze protection, and the documentation and inspection package are all configured to the duty.