About a week after the circuit breaker period began on April 7, residents of Sims Urban Oasis condominium saw a startling sight: Their swimming pools, which usually appear blue, had turned emerald green.
The change in colour was due to algae forming at the base of the pools, which were on the ground floor of the estate in Sims Drive.
A week after its management corporation was alerted, it received the nod from the National Environment Agency (NEA) on Sunday for the estate's pools to be cleaned.
The following day, pool cleaners brushed and vacuumed the bottom of the pools to remove the algae.
The condominium's residence manager Mark de Souza told The Straits Times on Wednesday that maintenance of the pools had stopped on April 6, in keeping with the circuit breaker measures.
According to previous NEA guidelines, only water treatment was allowed every fortnight, and this included increasing the free chlorine concentration in the pools to help manage algae growth.
Mr de Souza said the cleaners were not able to complete the cleaning of all six pools in the estate as "they could not enter the water due to the high level of chlorine".
Under NEA's April 5 guidelines, all swimming pools must stay closed from April 7 till June 1, as required by circuit breaker measures.
In response to queries, NEA said these guidelines had made it clear that pool cleaning was allowed during the circuit breaker period.
Safe distancing measures such as the number of treatment personnel allowed on site and the frequency of maintenance were covered in the guidelines, the agency added.
Many swimming pool maintenance companies have also gone ahead to remove algae and carry out other pool maintenance activities since the start of the circuit breaker period on April 7, it said.
Guidelines for pool maintenance
NEA guidelines for swimming pools while they are closed:
• Only two maintenance personnel can visit the site once every two weeks to do the necessary maintenance.
• Dose pool water with 5mg/L to 10 mg/L of chlorine every two weeks.
• Pumps can be operated to distribute chlorine throughout the pool for two to six hours, depending on the turnover rate.
Before reopening of swimming pools:
• All surfaces of the pools are to be brushed to remove algae.
• Restart pool filtration system and super-chlorinate the pool with 10 mg/L of chlorine for 24 hours to kill the algae.
• Vacuum pool and remove dead algae through draining to sewer.
• Backwash pool filtration system to ensure no dead algae trapped.
• Water samples have to pass all regulated limits stipulated in the Environmental Public Health (Swimming Pools) Regulations before the pools can be reopened for use.
All building owners, management corporations and town councils are required by PUB to do proper maintenance of water service installations during the circuit breaker period. These include:
• Reducing amount of water stored in the water tanks.
• Draining and refilling water tanks and pipes with fresh water.
• Flushing taps periodically.
• Turning on taps not used for over a week for five to 10 minutes to allow fresh water to fill the service pipes, before usage.
Michelle Ng and Vanessa Liu
Revised guidelines were released on Sunday, in which NEA provided further details on the types of swimming pool maintenance activities that are allowed throughout the circuit breaker period.
These include but are not limited to scrubbing, vacuuming and cleaning of pool surfaces, water treatment, clearing of strainers, and cleaning or backwashing of filters, said the agency.
Professor Ooi Eng Eong, deputy director of the emerging infectious diseases programme at Duke-NUS Medical School, said the only danger such algae poses is when residents swim in the pool before it is fully decontaminated.
The NEA spokesman also said building owners must maintain the closed swimming pools once every two weeks to minimise algae growth and prevent mosquito breeding. At such sessions, only two water treatment personnel can visit the site to carry out the task.
Owners whose pool contractors are barred from operating can seek help via an online feedback form on the NEA website or the myENV app.
National water agency PUB told ST it has reminded all building owners, management corporations and town councils to carry out proper maintenance of water service installations, such as water storage tanks and water pumps, during the circuit breaker period.
The required measures, which include reducing the amount of water stored in water tanks, must be carried out before business activity resumes, the PUB said.
"During the circuit breaker period, water consumption at many buildings and premises is expected to be lower than normal due to reduced activity," it added.
"Maintaining regular turnover of water tanks and flushing of pipes will ensure healthy levels of residual chlorine in the water supply and prevent harmful bacteria growth."