Water Tank in Buildings: Types, Rules and Maintenance

In many Singapore buildings, the water that reaches your tap has spent time in a water tank. Storage tanks smooth out demand, provide a reserve if supply is interrupted, and in tall buildings allow water to be distributed by gravity from roof level. Because stored water can deteriorate if a tank is poorly built or neglected, tanks used for drinking water are regulated more closely than most building services.

This article explains why tanks are used, the main types and their components, the PUB inspection and certification regime, the structural implications of storing a large weight of water, and the faults that most often affect tanks.

Why buildings use water tanks

PUB’s mains can supply fittings up to a certain height directly. Above that, water must be pumped. Following the national code of practice for water services, high-rise buildings commonly have a low-level tank that receives water from the mains, transfer pumps that lift it to a high-level tank on the roof, and a distribution system that feeds the floors below by gravity, with booster pumps for the top floors where gravity alone gives too little pressure. Some buildings use direct pumping systems that reduce or remove roof storage.

Storage also protects the building’s supply. If the mains are interrupted for repairs, residents continue to draw water from the tanks for a period, and the building’s demand peaks are buffered rather than drawn directly from the network.

Types of tank and their materials

Low-level or suction tanks at ground or basement level, feeding the transfer pumps.
High-level or roof tanks, from which water is distributed by gravity.
Landed-home tanks, sometimes on the roof or in a roof space, serving the house.
Non-potable tanks for rainwater harvesting, irrigation or flushing, which must be kept entirely separate from the drinking water system; see our article on rainwater harvesting.

Common materials include sectional panels of glass-reinforced plastic or stainless steel bolted together on a supporting frame, one-piece polyethylene tanks for smaller capacities, and in-situ reinforced concrete in some older buildings. Each has its own weak points: gaskets and bolted joints in sectional tanks, UV exposure in plastics, and cracking and lining failure in concrete.

The parts of a water tank

Inlet with float-operated valve, which closes as the water reaches the working level.
Outlet, set slightly above the tank floor so sediment is not drawn into the supply.
Overflow and warning pipes, which discharge visibly if the inlet valve fails, so the fault is noticed.
Drain or scour valve for emptying the tank during cleaning.
Vent with insect screen, letting air in and out as the level changes while excluding insects, birds and debris.
Lockable access cover, which prevents contamination and unauthorised entry. PUB’s requirements address tank security.
Ladder and platform for safe inspection access.

PUB inspection and certification

PUB requires any person responsible for the maintenance of a water service installation with a water storage tank to engage a Licensed Plumber at least once every 12 months to inspect the tank, clean and disinfect it where necessary, and certify it. Water samples are tested by an accredited laboratory against parameters that include residual chlorine, pH, turbidity and E. coli, and the tank must be fit and safe for storing water for human consumption. Failure to certify on time is an offence under the Public Utilities (Water Supply) Regulations.

It is the legal responsibility of MCSTs and building owners to keep the certification records. In HDB estates, Town Councils maintain the tanks on common property. PUB states that landed residential properties with a tank located after the sub-meter are exempt from mandatory certification but must still keep the tank clean. The governing requirements are in the Public Utilities (Water Supply) Regulations and SS 636, the Code of Practice for Water Services; check pub.gov.sg for the current version.

Where works involve the design of a plumbing system with a storage tank, PUB requires a Professional Engineer for the design and supervision of the works.

The structural side: water is heavy

A cubic metre of water weighs about a tonne. A roof tank of even modest capacity therefore places a substantial concentrated load on the structure, and that load is present permanently, not occasionally. Tanks sit on plinths or steel frames that spread the load to beams and columns designed to carry it.

That has practical consequences. Adding or enlarging a tank on the roof of a landed home, replacing a tank with a larger one, or placing tanks on a slab not designed for them can overload the structure. The supporting frame also needs to be checked for corrosion, particularly at bolted connections and bearing plates exposed to the weather. Our article on what a structural engineer does explains when such a check is needed. Leaks from roof tanks also find their way through roof slabs; the diagnosis is covered in our guide to roof leak repair.

Common faults with water tanks

Failed float valve, causing continuous overflow, or a stuck-closed valve leaving the tank empty.
Sediment accumulation on the tank floor, which can be stirred into the supply and discolour water at the taps.
Biofilm and contamination from damaged insect screens, poorly fitting covers, or stagnant water in tanks too large for actual demand.
Leaking joints in sectional tanks as gaskets age or bolts loosen.
Cracking in concrete tanks, and deterioration of internal linings.
Corrosion of steel supports, ladders and fixings.
Cross-connection, where a non-potable supply is wrongly connected to potable pipework — a serious hazard.

If your tap water suddenly appears discoloured or smells unusual, report it to the Town Council or managing agent, who can check the tanks. A point-of-use water filter is not a substitute for a properly maintained tank.

Frequently asked questions

How often must a water storage tank be inspected in Singapore?

PUB requires the person responsible to engage a Licensed Plumber at least once every 12 months to inspect the tank, clean and disinfect it where necessary, and certify it, with water samples tested by an accredited laboratory.

Who maintains the water tanks in an HDB block?

Water storage tanks on the common property of HDB estates are maintained by the Town Council, while in condominiums the MCST is responsible for maintenance and certification records.

Do landed homes need their water tanks certified?

PUB states that landed residential properties with a tank located after the sub-meter are exempt from mandatory certification, but owners must still keep the tank clean, so check pub.gov.sg for the current position.

Can I add a water tank to my roof?

A new or larger tank adds a heavy, permanent load and changes the plumbing system, so the structure should be checked by an engineer, PUB requires a Professional Engineer for plumbing systems with storage tanks, and the installation should be done by a Licensed Plumber.

Why is water from my tap brown after maintenance works?

Disturbance during tank cleaning or pipe works can stir up sediment, which normally clears after running the tap for a short time, but if it persists, report it to the Town Council or managing agent.

Adding a tank, or concerned about leaks and corrosion at a tank support? Talk to our consultancy or get in touch.