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Causes of water discolouration

26 June 2018
Causes of water discolouration


Singapore enjoys good quality tap water due to a robust water treatment process and a rigorous water quality monitoring programme that covers the entire water supply system. Our tap water is well within the World Health Organisation (WHO) drinking water guidelines and is safe to drink without boiling or further filtration. However, do you occasionally notice that your water appears discoloured or contain particles, and wondered why this happens? We reached out to Water Supply Network (WSN) Senior Engineer, Kok Yi, to answer some of the common burning questions about causes of water discolouration, as well as listen to some of his experiences dealing with such situations.

water discolouration

In an interview with Kok Yi, he shared that cause of discoloured water is due to the re-suspension of mineral sediments. These minute amount of minerals are inherent in our water and will settle at the base of the water tanks, water mains and also at the end point of the distributing pipes over time.

The common causes of discoloured water to the re-suspension of mineral sediments can be due to maintenance operations such as the routine cleaning of water tanks, flushing of service pipes in buildings by Town Councils, Management Corporation Strata Titles (MCSTs), building owners and the operation of fire hydrants. However, discoloured water can also occur as a result of corroded internal fittings within house premises or stagnant water in service pipes and water service installations as a result of infrequent use.

In addition, heavy drawoff from a water mains leak may also lead to the temporary re-suspension of the mineral sediments which appears as discoloured water at the customer's tap.  To clear brownish water from PUB's water mains, our officers will flush the water containing re-suspended mineral sediments out from the water mains in a controlled manner until the water clears up.

Corroded service pipes

Kok Yi shared that some of the common reports that his team receives on discoloured water is when customers notice brown stains on the cloth filters that they attach on their taps. He commented that they may see brownish deposits on their filters over time due to the minute amounts of minerals inherent in the water supply. "Discolouration of the filter will be noticeable when minerals absorbed in the filters are oxidised. PUB discourages the use of any filtration system as bacteria could grow on the filters if they are not maintained or replaced regularly." says Kok Yi.

Cloth Filter

Kok Yi also noted that PUB takes every single case of water discolouration into serious consideration. Feedback on discoloured water will be investigated to establish the cause and ensure that the PUB water supply is clean and clear. Often, Kok Yi and his team works closely with customers, Town Councils and building maintenance to ensure the water is fit for potable use.

Depending on findings, the engineers will conduct emergency pipeline operations isolate the source and prevent further discolouration if the source is from PUB water main. To clear brownish water from PUB's water mains, officers will flush the water containing re-suspended mineral sediments out from the water mains in a controlled manner until the water clears up. If the discolouration is from the PUB water mains, temporary water supply, such as water bags and/or water wagons, will be provided for the customers affected. However, if the source of discoloured water is within the customer premises, the officers in charge will advise the customer to rectify the problem by replacing or repairing the appliances or pipes.

If you do encounter discoloured water, Kok Yi advised customers to first run their taps and flush any water tanks inside their premises until the water runs clear. If the water has not cleared up after 10 to 15 minutes, customers can call PUB's hotline at 1800-CALL-PUB for assistance. Meanwhile, customers should also try to determine the source of the discoloured water. If the discoloured water is localised to be from a single appliance, this could indicate a faulty appliance. PUB officers also work very closely with Town Councils and SCDF to ensure maintenance operations are conducted with care to minimise discoloured water incidents.

On how customers can do their part to minimise water discolouration incidents, Kok Yi advised customers to always check that their appliances are in good working condition and replace them when there are signs of corrosion. Customers can also do their part to ensure corrosion resistance materials are used for their service pipes. He also noted that customers should flush the water before use, especially if water in their service pipes or water heater has been stagnant for a long period of time.