Can a fire water tank be built next to a wall?

If the buildings around you are closely packed and the space is limited, I personally think it’s possible to build against the wall. There are several views regarding the installation of fire water tanks: one suggests using the same tank for both fire-fighting water and domestic water. Another approach advocates separating the two. A fire water tank is a man-made structure used to store water for firefighting purposes, and it serves as an important supplement to natural water sources or municipal water supply systems. It is advisable to use the same pool for both fire-fighting water and water for domestic and industrial use; this not only reduces costs but also ensures that the water quality remains good. When using a common water tank, the fire-fighting water inlet must be located below other inlets, but not more than 6 meters below them. If necessary, an independent fire-fighting water tank can also be constructed.

Another view on fire water tanks is to advocate for the separate construction of living water tanks and fire water tanks. The following text is excerpted from the Internet. From the perspectives of water quality protection and regular testing and maintenance of fire pumps, this article discusses the inefficiencies of combined living and fire protection water tanks/containers, as well as the proper installation of check valves on the outlet pipes of elevated water tanks. It argues that separating the water tanks and using shared suction pipes plays a positive role in optimizing basement design, making more effective use of basement space, and reducing costs. 1 There are disadvantages to combined water tanks (containers) for domestic use and fire fighting. Due to their large capacity, such combined storage tanks result in a long cycle for water quality renewal for domestic use. Underground combined water storage tanks in high-rise buildings are required by regulations to store both indoor and outdoor fire-fighting water; domestic water accounts for less than 20% of the total stored water volume, the renewal cycle is well beyond 24 hours, and there is insufficient residual chlorine in the water, which facilitates the growth of bacteria and algae. To ensure water quality, secondary chlorination is necessary, which increases operating costs and causes management difficulties. The shared water storage tanks cause difficulties for the regular testing of fire pumps. The fire department requires that electric fire pumps be tested by running them for 5 to 10 minutes per month for inspection. During the trial run, in addition to checking whether the water pump is operating properly and whether the pressure levels are within normal ranges, it is also necessary to drain water for inspection. For jointly built water tanks, this process of draining water presents difficulties; if the water is drained into such tanks, it will inevitably contaminate the water quality ； If discharged directly into outdoor rainwater drains, the pressure will be too high, which can easily damage the drains; even if the pressure is reduced before discharge, there are still safety risks, and water is wasted as well. When using a roof water tank for fire testing, improper sealing of the check valve connecting the tank to the fire protection piping system leads to leaks, causing the water stored in the fire protection piping system to flow back into the tank and resulting in water quality contamination. When the fire protection piping system is connected to high-level water tanks in two or more towers, uneven water consumption in each tower causes the water level to change slowly. As the level reaches equilibrium, the water flow is not sufficient to close the check valves properly, resulting in leaks that contaminate the water quality. When the jointly constructed reservoir is filled with outdoor fire-fighting water, the water intake for outdoor fire trucks can also contaminate the water quality in the reservoir due to poor sealing. In summary, although the fire protection pipeline network and the domestic water pipeline network are installed separately, the use of shared storage tanks and elevated water tanks inevitably leads to contamination of the quality of domestic water. Therefore, by installing separate water storage tanks for domestic use and for firefighting purposes, the factors that could contaminate the quality of water used for domestic purposes are eliminated. The wastewater generated during the testing of fire pumps can be directly returned to the firefighting water tank, where the water stored in that tank helps to dissipate energy, thereby achieving water conservation. The significance of having separate water tanks for domestic use and firefighting purposes: Many people are concerned that having separate tanks for domestic water and firefighting water will increase costs and may cause the firefighting water to become contaminated and smelly. In fact, these problems can be completely avoided with proper measures. As long as the fire-fighting water stored is qualified tap water, an appropriate amount of chlorophenol fungicide is added during the filling of the reservoir, and necessary dust and insect prevention measures are in place at the openings and ventilation areas of the reservoir, the water stored will not deteriorate or become foul-smelling. Of course, it is still necessary to empty the stored water and replace it once a year. Separate storage tanks for domestic water and fire-fighting water will not increase costs. In actual engineering design, separating the storage tanks plays a positive role in optimizing the design of basements, making effective use of their space, and reducing costs. Separate storage tanks are used, and the total water storage capacity does not change as the number of tanks increases. When reservoirs are built together, the water tanks must take effective measures in accordance with regulatory requirements to prevent the fire-fighting water from being used unintentionally; when they are built separately, there is no such issue of unintended use. In jointly constructed reservoirs, it is not allowed to use the floor slab and side walls of the building’s basement as the bottom and sides of the reservoir; however, when the space above the reservoir roof is a clean room, it is permissible to use that floor slab as part of the reservoir roof ； When the upper layer above the pool roof is not a cleanroom, a separate pool roof must be installed to ensure the quality of domestic water, which poses many difficulties in terms of design. Fire storage tanks can often utilize the basement’s floor, side walls, and ceiling as the tank bottom, walls, and roof respectively; there is no need to install guide walls inside the tank, which increases the effective water depth, reduces the area occupied by the tank, and lowers construction costs. Land for urban renewal is extremely scarce, resulting in the basements of many buildings having highly irregular shapes. To ensure space for parking spaces and driveways in the basement garage, equipment rooms are usually located in areas with irregular shapes that do not interfere with the parking spaces. When using combined water storage tanks for domestic use and fire protection purposes, it is very difficult to ensure that the bottom, walls, and roof of such tanks meet the standards required for domestic water storage tanks. A common approach is to restrict the functions of the buildings above the tank roof or to increase the area occupied by the tank (thereby reducing the effective water depth) in order to create a separate roof, which increases the construction costs. By separating the living water tank from the fire-fighting water tank, it is sufficient to find a small area with favorable conditions at the top for placing the living water tank, while using the remaining areas as fire-fighting water tanks. This approach provides great flexibility in design; the effective depth of the fire-fighting water tank increases, the land area required is reduced, and the project cost is lowered. The separately constructed fire water tanks are required by regulations to store the amount of fire-fighting water needed for both indoor and outdoor use during the duration of a fire. Due to their large water storage capacity, these tanks are usually arranged in separate sections. In practical projects, since the domestic water storage tanks are located in more favorable positions, even though the capacity of the fire protection water storage tanks is ensured as a result of this sectional design, it becomes difficult to arrange individual suction pipes for each fire pump. Article 7.5.4 of the Code GB 50045—95 stipulates that a set of fire pumps should have no fewer than two suction pipes; when one of them is damaged or needs repair, the remaining suction pipes must still be able to handle the entire volume of water. In other words, the use of shared suction pipes is allowed, which simplifies the design, arranges the water pumps in an orderly manner, and facilitates management and maintenance. When using a common suction pipe, the following points should be noted: ① The fire pump must be capable of starting with self-priming; if self-priming start is not guaranteed, each pump must have its own separate suction pipe. ② The shared suction pipe should have a diameter selected based on the maximum possible flow rate, with the flow velocity being kept at around 0.5 m/s; the flow velocity in the water pump branch pipes should be between 0.8 and 1.2 m/s. ③ The connection between each water pump branch pipe and the common suction pipe is made using a tee with equal pipe levels; the branch pipe and the water pump’s suction inlet are connected using eccentric tees with equal pipe levels, to ensure that the suction pipe can discharge air automatically. ④ Gate valves should be installed on each water pump branch pipe, with gate valves being commonly used. 3 Selection and installation of the check valve on the fire water outlet pipe of the high-level common water tank: The check valve on the outlet pipe of the high-level water tank opens due to the static pressure in the tank; generally, this static pressure is only in the range of a few dozen kPa. Therefore, the check valve chosen must have the characteristics of a low opening pressure and fast closing speed. Saddle check valves, low-resistance slow-closing check valves, and noise-suppressing check valves cannot meet the requirements; the most suitable check valve is a swing check valve. When a swing check valve is used, it should be installed at a height of not less than 1.5 kPa above the bottom of the water tank, and must be installed on a horizontal pipe section. Many textbooks and design manuals arbitrarily place check valves on vertical pipes in the schematic diagrams of water fire protection systems, leading many designers to mistakenly believe that as long as a check valve with a low opening pressure is selected, it will meet the requirements regardless of whether the valve is installed horizontally or vertically. When the check valve on the fire-fighting outlet pipe of the common water tank is installed vertically, the valve disc of the check valve hangs down under the effect of gravity and remains open over time. As a result, the water stored in the fire-fighting system comes into direct contact with the domestic water in the upper-level common water tank. When there are slight fluctuations in pressure within the fire-fighting system, some of the water flows into the common water tank, contaminating the domestic water. This situation is common in multi-story residential buildings. The fire department requires that indoor fire protection systems be connected to the municipal water supply pipes. Since the outlet of the fire water pipe is at a lower elevation than the inlet of the common water tank, when the pressure in the municipal water supply network drops and the water pressure is not sufficient to close the vertical check valve, tap water flows directly into the common high-level water tank through the fire protection system, resulting in water quality contamination. This problem prevents the eradication of red worm infestations in the common water tanks of residential buildings in southern cities. Installing the check valve horizontally yields significant results, as it reduces the frequency of red worm occurrences. 4 Conclusions ① From the perspective of water quality protection and regular testing and maintenance of fire pumps, domestic water tanks, fire water tanks, piping systems, and elevated water tanks should all be installed separately and independently. ② The use of a shared water intake simplifies the design and facilitates the maintenance of the equipment. ③ Separate water storage tanks play a positive role in optimizing basement design, making effective use of basement space, and reducing costs. ④ The check valve on the outlet pipe of the high-level water tank must be installed horizontally.

It should be fine, as long as it doesn’t prevent fire trucks from accessing water, there’s no major issue!