Turning the tide against burst pipes

PUBLISHED : Sunday, 12 December, 2010, 12:00am
UPDATED : Sunday, 12 December, 2010, 12:00am

A spate of water main bursts this year has left some wondering if Hong Kong is sitting on a ticking time bomb of ageing water pipes. The most recent burst, last week, left thousands in Taikoo Shing and other eastern Hong Kong Island estates without fresh water for 12 hours.

The bursts have been blamed on old water pipes that have reached the end of their service lives, making them vulnerable to leaks.

But a contractor who has replaced many old pipes says there is nothing to worry about because the government is investing HK$21.81 billion to replace more than a third of its water mains.

'The Hong Kong government has been approaching the issue systematically since 2000 and is well on the way to rehabilitating and replacing 3,000 kilometres of water mains by 2015,' said Alan Man, managing director and vice-president at Black & Veatch, one of several contractors working for the government's water mains replacement and rehabilitation programme.

The 3,000 kilometres of mains that will be replaced make up 38 per cent of the city's total water distribution network. 1,390 kilometres of mains have already been replaced, with the rest scheduled to be replaced by 2015.

More than a quarter of Hong Kong's water mains are over 30 years old, which is the normal lifespan for many galvanised and cast iron pipes. Since Hong Kong's varied topography can create huge build-ups of pressure inside the pipes, water leakage is a constant problem, which can sometimes lead to burst pipes.

Recently, to fight leakage, the government has been installing pressure-reducing valves inside pipes, which has cut the percentage of water lost to leaks from 25 per cent in 1999 to 20 per cent today. The number of water main bursts has decreased even more substantially, from 2,479 in the 2000/01 financial year to 988 in 2009/10, according to the Water Supplies Department.

Replacing old pipes has not been easy. 'Improving the buried infrastructure in a dense environment like Hong Kong is sometimes like threading the eye of a needle,' said Man. 'You do not have the luxury of simply opening up the road and laying a new pipe to replace the old.'

As a result, new technologies have been developed to replace water mains without digging into the ground. In one case, workers actually entered the water main that runs underneath the Lion Rock Tunnel to reinforce its walls by hand. They used a fibreglass fabric that is normally used to patch cracks on boat hulls.

Underneath the Tolo Highway, a new polyethylene pipe was inserted into a 3 kilometre stretch of old pipe, a technique known as swage lining. It was the first time in the world such a procedure had been completed on such a long water main.

Most of the new water mains being installed are made from polyethylene and ductile iron, which have an expected lifespan of at least 50 years. By the time the replacement programme ends in 2015, nearly two-thirds of Hong Kong's water pipes will be less than 10 years old.