Chlorine levels in parts of city ‘good enough for swimming pool’

Some Christchurch residents might be drinking what is effectively swimming pool water.

The city council’s tests of the newly-chlorinated public drinking water supply have shown, on average, the chlorine level is higher than what residents were told to expect.

Three-quarters of the 1395 samples the council has tested since chlorination started in March show either under-chlorination or overchlorination, leaving a quarter of samples showing the planned levels.

More than 10 per cent of the council’s tests recorded a chlorine level in the same range as that of a public swimming pool. Another two thirds of the samples showed levels below effective chlorination.

The council is testing at properties next to the city’s 56 pump stations and at three locations a short distance from where each dose is administered.

Christchurch residents have complained about the taste and smell of tap water since chlorination was rolled out.

James Martin, who lives near one of the pump areas, said he was a ‘‘canary in the coal mine’’ when it came to chlorine levels because he has hyper-sensitive skin.

Martin said his eyes burned while he cleaned dishes and his skin hurt in the shower. One day, he said the ‘‘vapours’’ slightly burnt his skin.

That day, he tested his tap water with chlorine-measuring equipment he uses for his pool. It measured a level of 4 parts per million (ppm) to 4.5ppm a litre – higher than recommended for public swimming pools – though he acknowledged pool chlorine testing equipment, which typically measures in 0.5ppm increments, was not as accurate as the equipment used by water treatment specialists.

Martin tested the water several days later and it had dropped to between 1ppm and 1.5ppm a litre – still within the expected level for swimming pools.

The science

When the council began chlorinating, it said residents could expect to find 0.2ppm to 0.5ppm of chlorine per litre.

The council has since recorded an average of 0.64ppm over 1395 tests, with one recording 1.97ppm. Swimming pools are typically chlorinated between 1ppm to 3ppm.

Of the samples tested, 10.7 per cent showed levels above 1.1ppm; 0.5 per cent above 1.5ppm; and 65 per cent were below the 0.2ppm cutoff for effective chlorination.

The United States Centers for Disease Control and Prevention

‘‘I got out of the shower last night and smelled like I’d just climbed out of Pioneer Pool. It’s revolting.’’ Waimairi Beach resident Sharon Brophy

(CDCP) identifies a level of 10ppm as ‘‘immediately dangerous to life and health’’. After a level of 5ppm, the CDCP recommends the use of a gas mask.

The smell and taste of chlorinated water is caused by chloramine, which is formed when chlorine binds with organic compounds such as bacteria or algae. The council does not test for chloramine levels.

‘Problem not at the pumps’

Martin, a computer scientist with a chemistry degree, thought the problem was that the chlorine tended to concentrate on the periphery of the 56 pump stations. He said the council needed to install water churns to agitate the water at all stages along the network.

‘‘The problem is not at the pumps. You’ll find people complaining in the further away areas.’’

City services general manager David Adamson said chlorine build up had been identified as a potential issue, but was ‘‘not seen as an issue due to the concentration, previous experience with chlorine dosing and the temporary nature of the installation’’. The council did not recommend people use pool devices to test their tap water.

Martin said he planned to install a $2500 water purification system in his house to prevent further problems.

‘‘I need it for my health, between my daughter and my wife’s asthma and my skin reaction.’’

‘It’s revolting’

People on social networking site Neighbourly have claimed they will not drink the water coming out of their taps because of the taste.

‘‘[We] have resorted to water drops ... and our friends and family from up north are choosing to buy bottled water as they can’t drink it,’’ Danielle Kimberly, from Aranui, said.

Keryn McIntyre, from Mairehau, said the chlorine taste at her home was ‘‘very strong’’ and she could not drink the water.

Sharon Brophy, of Waimairi Beach, said she could smell chlorine when she used her shower.

‘‘I got out of the shower last night and smelled like I’d just climbed out of Pioneer Pool. It’s revolting.’’