A recent report said that "Hyflux failed to replace poorly performing membranes in 2017, which affected the quantity and quality of Tuaspring water" (PUB to take over Tuaspring to safeguard water security, April 18).

Environment and Water Resources Minister Masagos Zulkifli said earlier this month that the water supplied to consumers is safe to use and drink, and that national water agency PUB conducts many tests to ensure water safety.

The question is: How exactly does PUB ensure the water is safe to drink when poorly performing membranes affected the quality of Tuaspring water?

The membranes have many purposes. They filter out heavy metal contaminants, chemicals, bacteria and viruses. Although chlorine is added to water, it does not kill certain viruses and cysts.

Furthermore, the water from Tuaspring plant is added to treated water from other plants, reservoirs and Newater.

So if PUB conducted water test sampling at taps and various water points, the samples might not have contained contaminated water from Tuaspring, as water from there might have been mixed with treated water from elsewhere.

The question is whether PUB conducted tests at the Tuaspring plant before the water was mixed when the membranes failed to work properly.

Wong Chee Meng