Our public swimming pools: How clean are they?

Our public swimming pools: How clean are they?

Ten pools here were tested for ammonia (a by-product of urine) and other substances. The results were not pretty, as the programme Why It Matters found out.

How clean are our public swimming pools? Why It Matters tests the water from 10 pools for ammonia, which is found in urine. 

SINGAPORE: Mr Sathananthan Selvadurai generally avoids public pools.

Having spent more than a decade designing water treatment technology, including for swimming pools, this lecturer at Ngee Ann Polytechnic’s School of Life Sciences and Chemical Technology knows full well about the impurities that make their way into these pools.

These include saliva, urine and other body waste, besides solid particles such as dirt, leaves, bandages, and sometimes, cockroaches.

The problem, however, lies in the amount of pollutants that can be found. Experts caution that too much ammonia, for example, can react with chemicals in the pool to cause respiratory problems and eye irritation.

(Read: High rates of respiratory problems linked to indoor lifeguard work)

“The main sources of ammonia in swimming pools are brought by swimmers: Urine, body waste and also mucus liquid. These are the main contaminants, which contribute to the increase in ammonia concentration,” Mr Sathananthan said.

His concerns may not be unfounded. Earlier this year, Canadian researchers figured out a way to measure the amount of urine in swimming pools, and what they found after collecting samples from 31 pools was startling.

WIM pee pool 5

In one pool, the researchers found 75 litres of urine over three weeks, while in another pool they tested, there was some 30 litres of urine.

There has not been a similar study done in Singapore, but there is a test, known as the ammonia chlorine test, that can show if there is a presence of ammonia in pools here.

Producers of Channel NewsAsia's Why It Matters programme collected water samples from 10 out of Singapore's 24 public pools. The 10 were in Toa Payoh, Bukit Batok, Clementi, Yishun, Bedok, Jurong East, Bishan, Choa Chu Kang, Hougang and Ang Mo Kio. (Watch the episode here.)

These samples were tested with a reagent in Mr Sathananthan’s laboratory. Ammonia was found in all of them, though the levels - going by the shades of pink, which signals the presence of ammonia - appeared to vary among the pools.

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The results of the ammonia test on samples from the 10 pools.

It is impossible, noted Mr Sathananthan, to expect zero trace of ammonia.


The question is whether there is any cause for concern for the public.

Tampines Swimming Complex senior lifeguard Derrick Yeo, who ensures that the pool meets the safety requirements set by the National Environmental Agency (NEA), said water samples from public pools like at Tampines are regularly sent for testing for bacteria and germs.

This follows the Environmental Public Health Act, which requires swimming pool operators to meet certain conditions before their pools can be used by the public.

The process includes arranging for the pool water to be analysed by accredited laboratories for chemical and bacteriological quality at least monthly. And these test results must be submitted to the NEA, according to its website.

“We have passed the test all this while … Conditions so far are acceptable,” Mr Yeo said, before adding a caveat. “If, for example, more people are urinating in the pool, those conditions might change.”

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The fact is that most public pool operators replace only 10 to 12 per cent of their water with fresh water every few days, which is why ammonia in the pools cannot be completely removed.

And the water in most pools is never completely replaced from the day they open.


To make a public pool safe for swimming, the water – besides being flushed out and replenished regularly – typically undergoes three stages of filtration to remove solid particles, and after that, a final stage of chlorination.

However, impurities such as mucus or urine will remain even after the entire treatment process, said Mr Sathananthan. So chlorine is constantly pumped into the pool to kill most of the germs and bacteria.

Mr Yeo noted: “The chlorine can’t be so strong that it kills the germs and bacteria immediately. So it has to be (added) over a period of time, if not it’ll be harmful to the skin when the chlorine level is too high.”

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Vacuum cleaners remove sediment on the pool floor.

To remove sediments that have settled on the pool floor – including debris, hair and dirt – vacuum cleaners are used once a week.

On top of that, at Tampines Swimming Complex, some six divers spend at least six hours every week scrubbing the tiles of the floor to prevent the growth of algae, which could otherwise become a breeding ground for bacteria.

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Divers scrub the tiles to prevent the growth of algae.

There is also one other cleaning method: Super chlorination, when a large amount of chlorine is added to the pool in order to destroy germs.

“For public pools, it’s difficult to do this because they (the operators) need to close off the pool, which is inconvenient for the public,” said Mr Sathananthan.

If someone defecates in the pool, however, there is no other choice but to close it, vacuum it thoroughly and do a super chlorination, said Mr Yeo, who has encountered this situation before.

“So we actually encourage and educate our guests to take a toilet break whenever they need (it),” he said.

Watch: Keeping the waters clean enough (3:38)


In a sense, the initial responsibility for pool maintenance still lies with users practising proper pool hygiene - such as showering before jumping in.

For example, faecal matter, which can be invisible to the naked eye, can be present on a swimmer’s hands and skin. A study by the United States’ Centers for Disease Control and Prevention found that the average person carries 0.14 grams of faeces on his or her rear end. Children can carry up to 10 grams of faecal matter.

Senior microbiologist Renugopal from Marchwood Laboratory Services, which runs bacterial tests on various water sources in Singapore, said harmful bacteria such as salmonella, E coli and coliform are found in faecal matter and could cause diarrhoea and dysentery if ingested.

Showering before entering the pool is also important to remove organic matter such as hair wax, cosmetic make-up and body oil.

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Always shower before using the pool.

A 2014 study by the US’ National Swimming Pool Foundation found that these organic matter react with chlorine to form by-products such as trihalomethanes and chloramines, which, if produced in large enough quantities could cause respiratory problems for swimmers.

However, not all swimmers here shower before jumping into the pool. At one swimming complex, for instance, only 21 people were observed to have done so in the span of an hour, out of the hundreds using the pool.

Mr Renugopal said: “Shower before going into the swimming pool because it’s good for other people too, not only us.”

And with Singapore’s swimming pool attendance numbers at more than seven million last year, users can make quite a difference.

Watch this episode of Why It Matters here (new episodes every Monday).

Source: CNA/yv