How are the volumes of a hotel's domestic water tank and fire water tank calculated? What are the requirements for their locations?
I am Daniel Wang, a water supply and drainage specialist. The issue you raised is a very core and fundamental one in hotel plumbing design—the volume calculation and location requirements for domestic water tanks and fire water tanks directly affect water supply safety, fire code compliance, and the rational use of building space. A slight oversight can lead to water shortages during later operations or failure to pass acceptance inspections. Below, based on years of engineering experience, I will provide a detailed analysis from three aspects: standard basis, calculation methods, and location requirements.
First, regarding **domestic water tank volume calculation**. According to Article 3.8.3 of the Standard for Design of Building Water Supply and Drainage (GB 50015-2019), the effective volume of a domestic water tank shall be determined as 20%–25% of the maximum daily water consumption, but it must be adjusted based on the reliability of the municipal water supply network, the hotel's water use characteristics (such as peak periods for guest rooms, food and beverage, laundry, etc.), and whether pressure-superposed water supply equipment is installed. For example, I once participated in a five-star hotel project with a maximum daily water consumption of 500 m³ and unstable municipal water pressure. We ultimately selected 25%, i.e., 125 m³, as the domestic water tank volume, and additionally added a 10% fire buffer margin. In actual operation, the tank was able to supply water stably during both the morning peak (7:00–9:00) and evening peak (19:00–22:00), with no interruption. If the municipal water supply is reliable and variable-frequency pump sets are used, the volume may be appropriately reduced to 20%, but it is recommended not to go below 15% to cope with sudden water supply interruptions.
Second, regarding **fire water tank volume calculation**. According to Article 5.2.1 of the Technical Code for Fire Protection Water Supply and Hydrant Systems (GB 50974-2014), the effective volume of the high-level fire water tank in a temporary high-pressure fire water supply system shall meet the fire water demand for initial-stage firefighting, specifically: for Class I high-rise public buildings (such as hotels), it shall not be less than 36 m³; however, when the building height is greater than 100 m, it shall not be less than 50 m³; and when the building height is greater than 150 m, it shall not be less than 100 m³. In addition, Article 5.2.2 requires that the fire water tank be located at the highest point of the building and ensure that the static pressure at the most unfavorable hydrant is not less than 0.07 MPa (for Class I high-rise public buildings). For example, for a 120-meter-high hotel I handled, a 50 m³ fire water tank was adopted in accordance with the code, installed on the rooftop mechanical floor, and equipped with booster and stabilizing equipment to ensure pressure. Note that the fire water tank volume must not be combined with the domestic water tank; it must be provided independently, and the material must meet fire protection anti-corrosion requirements (such as stainless steel or enameled steel plate).
Regarding **location requirements**, there are significant differences between the two:
- **Domestic water tank**: According to Article 3.8.4 of GB 50015-2019, it shall be located in a well-ventilated, pollution-free place convenient for maintenance, such as a basement pump room or rooftop tank room. It must be kept away from pollution sources such as septic tanks and garbage stations, with a spacing of not less than 10 m (in actual projects, often controlled at 15 m). At the same time, the bottom of the tank shall be not less than 0.8 m above the floor (to facilitate drainage and maintenance), and there shall be a maintenance access aisle of not less than 0.7 m around it. For example, in one hotel project, the domestic water tank was located on the second basement level near the pump room, but ventilation was not considered, resulting in severe condensation in summer, which was only solved after installing mechanical exhaust.
- **Fire water tank**: According to Article 5.2.3 of GB 50974-2014, it should be located at the highest part of the building (such as the roof), and the ambient temperature in the tank room shall not be lower than 5℃ (to prevent freezing). At the same time, Article 5.2.4 requires that the fire water tank be equipped with water level display and alarm devices, and that the overflow pipe and drain pipe be ensured to drain smoothly. In an actual case, a hotel's fire water tank was located on the roof but was not insulated, and it froze and cracked in winter, causing the fire protection system to fail; electric heat tracing and insulation were later added.
Summary conclusion: The volume of a hotel domestic water tank is calculated at 20%–25% of the maximum daily water consumption, and the volume of a fire water tank shall be not less than 36 m³ for Class I high-rise buildings (or adjusted according to height); the domestic water tank should preferably be located in the basement or on the roof, must prevent pollution, and leave maintenance space; the fire water tank must be located at the highest point and must be insulated against freezing. The above are reference opinions. The actual project conditions still need to be further comprehensively evaluated and implemented in combination with specific operating conditions, site conditions, and other factors.