Integrated Domestic and Fire Water System: Design, Sizing, and Compliance Guide

On a typical 54-meter residential tower, the fire-flow code alone forces a 288 m³ reserve — 40 liters per second for two hours under GB 50974-2014. Add a 50 m³ domestic buffer, and the project now faces two tanks, two pump rooms, and roughly 30–40% more mechanical floor area than an integrated domestic and fire water system would require. An integrated design delivers the identical fire reserve with about one-third less footprint, but only when the tank partition, hydraulic separation, and pump priority logic are engineered as one package.

Content

1 What an Integrated Domestic and Fire Water System Actually Does
2 Code Rules That Allow an Integrated Domestic and Fire Water System
3 Sizing the Integrated Domestic and Fire Water Tank
4 Pump Configuration and Control in the Combined Station
5 What Integrated Systems Save — and Where They Add Risk
- 5.1 Design gains
- 5.2 Duties to manage
6 Keeping the Integrated System Code-Ready
7 Integrated System Questions, Answered

What an Integrated Domestic and Fire Water System Actually Does

An integrated domestic and fire water system is a single-site water supply layout in which domestic and fire-fighting services share one tank enclosure and one pump station, while keeping completely independent pump sets, pressure zones, and reserve protection.

The shared element is the civil structure — tank panels, foundation, roof, pump-room walls, and access — not the water volume. Fire water stays in a dedicated compartment. Domestic pumps draw only from the domestic compartment, and a raised fire outlet or overflow weir guarantees that no domestic drawdown can lower the fire reserve.

Common tank shell with an internal partition or siphon-breaking weir between the two compartments
Dedicated fire pump set (duty and backup) connected only to the fire reserve
Domestic booster set with VFD constant-pressure control, drawing only from the domestic compartment
One control panel with interlocks that prioritize fire duty and trigger alarm routing
Check valves and backflow protection at every cross-connection point

The weir serves as the legal separation device: the domestic drawdown line sits above the fire reserve's normal water level, so no household drawdown can open the fire compartment. Inspectors look for this detail first.

Core definition

An integrated domestic and fire water system is a configuration where domestic and fire services share a tank structure and pump enclosure but retain dedicated pump sets, pressure zones, and reserve-water protection, so routine domestic use can never consume the legally required fire reserve.

Integrated Domestic and Fire Protection Pumping StationThis combined station houses dedicated domestic and fire pump sets within one enclosure, with fire reserve protection and modular design. It suits sites needing efficient water supply and code-compliant fire protection in a single system.View Product →

Code Rules That Allow an Integrated Domestic and Fire Water System

Integration is legal in most jurisdictions, but only when the fire reserve remains fully dedicated. IFC Section 903.3.5.1 permits a domestic tap on a combined service where an approved backflow preventer protects the sprinkler supply, and NFPA 22 applies the same logic to gravity tanks: fire storage must stay available after prolonged domestic drawdown. In China, GB 50974-2014 requires hydraulic isolation so that domestic pumps physically cannot reach the fire reserve.

Typical comparison for a 54 m residential block with a 288 m³ fire reserve
Criterion	Separate systems	Integrated system
Fire reserve integrity	Fully independent	Weir or raised outlet protection
Combined tank footprint	About 96 m²	About 66 m²
Pump room floor area	About 54 m²	About 36 m²
Cross-connection exposure	Low, duplicated piping	Check valves at every tap
Approval process	Straightforward	Authority review of separation detail

Three failures repeat in design review

The overflow weir is set too low, the fire-pump suction is not taken from the lowest point of the fire compartment, or the domestic booster draws directly from the fire zone without an intermediate break tank. All three are structural details, not control settings.

Sizing the Integrated Domestic and Fire Water Tank

Tank sizing starts with the fire reserve, because that number is fixed by code; domestic volume is then added as a regulation and emergency buffer.

For fire, use the governing design flow and duration. A Class 1 high-rise residence under GB 50974 needs 40 L/s for two hours — exactly 288 m³. Commercial occupancies under IFC and NFPA 13 land between roughly 95 and 570 m³ depending on hazard classification. For domestic storage, add 15–25% of the daily water demand; a 100-to-150-apartment building typically needs 40–80 m³.

Total specified volume therefore lands near 355 m³ — slightly above the 348 m³ of two separate tanks — because the integration gain is structural, not volumetric. What the owner saves is roughly 50 m² of floor area, one foundation, and the cost of a second equipment room.

30%

Combined mechanical floor area drops from about 150 m² to about 100 m² when a 288 m³ fire reserve and a 50 m³ domestic buffer share one tank shell, one foundation, and one equipment room.

The integrated tank volume is the sum of both reserves, plus the dead volume below the fire outlet. For retrofit work with limited access, specify bolted stainless or modular BDF panels; for occupied basements, welded 304/316 stainless sections give a tighter envelope and easier cleaning.

Corrosion-Resistant Domestic and Fire Water Storage TankA rectangular tank made of stainless or galvanized steel with sealed panel construction, offering large capacity for both daily use and initial fire response. Its sturdy design and corrosion resistance ensure reliable water supply and fire reserve availability.View Product →

Pump Configuration and Control in the Combined Station

A combined station runs two completely separate pump sets with a control hierarchy that makes fire demand absolute.

The fire pump set — duty plus backup — must comply with NFPA 20 or GB 27898, start on pressure drop, flow switch, or fire alarm signal, and never be VFD-modulated in a way that delays full-flow delivery. The backup pump takes suction from the same fire compartment with a separate power feed, so a single electrical fault cannot disable fire protection. The domestic set uses horizontal multistage or end-suction pumps under VFD constant-pressure control, with a small expansion tank for night-time leakage. The shared risk is pressure feedback: when the fire pump starts, domestic controllers must not interpret the resulting pressure spike as a domestic event.

Control hierarchy

Fire demand is absolute. A fire start signal locks out domestic duty, opens alarm routing, and forces the fire pump to rated flow regardless of tank level.

Prefabricated integrated stations — including units from Jiangsu Mingxing Water Supply Equipment Co., Ltd. — arrive with the separation weir and interlock logic pre-installed, which reduces field mistakes during commissioning.

Smart Fire-Fighting Water Supply System with Remote MonitoringThis IoT-enabled system transmits fire pool levels, pump status, pressures, and power data to mobile or computer terminals, enabling real-time management. It provides data support for maintenance and safe operation, improving oversight of fire protection equipment.View Product →

What Integrated Systems Save — and Where They Add Risk

Measured against separate systems on the same site, integrated domestic and fire water systems cut floor area by about 30%, tank material by 12–20%, and installation time by two to three weeks.

Integrated vs separate water systems on a 54 m residential block (baseline = 100)

Values are percentages of a separate-system baseline; lower is better.

Design gains

Basement footprint reduced by roughly one-third
One enclosure, one foundation, one set of level instruments
Fewer interconnecting pipes between separate rooms
Commissioning and inspection combined into one sequence

Duties to manage

Hydraulic separation must be proven on drawings before fabrication
Fire reserve must be re-verified after any later tank retrofit
Maintenance access must never disturb the fire-compartment water level
Backflow assemblies require scheduled testing under local code

Keeping the Integrated System Code-Ready

A combined system passes inspection only when the fire reserve, its separation structure, and the interlock logic are tested exactly as installed.

Weekly: start the domestic pump normally and confirm the fire-compartment level stays unchanged.
Monthly: test the jockey pump and check both check valves for reverse flow.
Quarterly: simulate domestic drawdown to the weir limit and confirm fire makeup stays closed.
Annually: run a full-flow fire-pump test at rated capacity and have a licensed tester verify the backflow assembly.

Inspect the weir visually on every visit; debris and paint overspray are the two most common blockages found on older installations. Keep the fire outlet unobstructed, and verify the interlock on every equipment-room visit. If your project needs a specific layout, application engineers can review the tank partition and pump schedule before fabrication.

Site note

Most post-commissioning failures come from the weir being treated as a maintenance detail rather than a safety device. It is a structural control element, and it deserves the same review schedule as the fire pump.

Integrated System Questions, Answered

Can domestic water and fire water share one tank?

Yes, when the fire reserve is hydraulically protected by a raised outlet, weir, or siphon-breaking partition, and when the local authority approves the separation detail. The fire volume must stay untouchable by domestic demand at all times.

Which codes permit an integrated domestic and fire water system?

IFC 903.3.5.1 and NFPA 22 allow combined services with approved backflow and separation provisions. In China, GB 50974-2014 governs fire-reserve isolation. Local amendments may add requirements, so early authority review is standard practice.

How much space does integration actually save?

For a 54 m residential block with a 288 m³ fire reserve, an integrated layout reduces combined tank and pump-room floor area from about 150 m² to about 100 m² — a reduction of roughly one-third.

What is the most common cause of failure in integrated systems?

The weir or siphon break. When it is installed too low, blocked, or modified during later works, domestic drawdown can erode the fire reserve without producing any visible alarm.