True, many AC pipes have already reached the end of their useful life and require rehabilitation or replacement. But some are still in good serviceable condition particularly those that had been laid with good workmanship and in areas not subject to high water pressures and vehicular traffic loading.

Like AC pipes, many other types of pipes similarly require rehabilitation and replacement. This is mainly due to poor workmanship during installation and jointing, unsuitable ground conditions for their use and corrosion of metallic fittings. In addition, changes in environment of the pipe brought about by increased vehicular traffic loading, redevelopment and changes in water pressures in the system also lead to breakage of pipelines.

Pipeline leakage has always been a perennial problem in Malaysia's water supply distribution systems. Analysis of available data shows that pipeline leakage in Selangor and Kuala Lumpur is ever increasing. The national study on non-revenue water conducted in 1988 shows the system leakage then in Selangor and Kuala Lumpur was 2,400 litres per one kilometer of mains in one hour (l/km/h). The corresponding figure for year 2000 was nearly 3,000 l/km/h. This means that not only are old pipes leaking more severely, but the newly-laid pipes are leaking too!

All the above is borne out by high levels of pipe leakage reported in some newer housing areas like SS 25 in Shah Alam where mild steel pipes were used and Kota Kemuning where uPVC pipes were used.

So, to reduce pipe leakage, replacement should not be confined to AC pipes only. But, is pipe leakage really the main culprit for dirty tap water in the Klang Valley? If it is, why is it that most complaints on dirty tap water are raised only in recent times while pipe leakage has always been a perennial problem all along?

Also, other States have similar AC pipes in their distribution systems. How is it that we do not hear frequent complaints of dirty tap water in those States?

Certainly, pipe leakage is not the main cause of dirty tap water. If pipe repairs were carried out promptly with adequate supervision and the affected pipeline flushed after repair, little amount of sediments would remain in the system.

In traditional water treatment processes it is not possible to completely eliminate all traces of dissolved or suspended matters. These, together with sediments resulting from poor pipe-repair practice, would accumulate and settle over the years at the bottom and wall of reservoirs and pipes. As long as the flow pattern, both in direction and velocity, in a water supply distribution system remains substantially the same, the accumulated layer of sediment would not slough off from pipe walls and water coming out of taps would remain clear. However, if there is a reverse direction of flow or an increase in flow rate, the residues would be stirred up, re-suspended and ultimately reach the consumers' taps. And this is the main cause of today's dirty tap water.

Clearly, the obvious solution is to flush out residues already accumulated in the distribution networks. Leak or no leak, all reservoirs and distribution pipelines required periodic flushing and scouring to remove accumulated sediments in bottom and wall of reservoirs and pipes. This should have been a normal maintenance practice for all water supply distribution systems.

A feeble attempt (Ops Cuci) by Selangor Waterworks to flush the reservoirs and pipelines in Petaling Jaya was initiated late last year. Though this maintenance works was already 25 years late, the authorities decided to stop this work because of the end-of-the year festive season. Then the recent water shortage further postpones the re-commencement of the work.

Therefore the main cause of dirty tap water is attributable to a lack of commitment and efficiency of Selangor Waterworks. With an ingrained and long-standing "out-of-sight, out-of-mind" philosophy on water distribution systems, it is not surprising at all to find that the authorities responsible to provide clean water to the public has not formulated any long-term maintenance program to achieve this objective.

Clearly, to put the blame squarely on AC pipes every time the subject of dirty tap water is raised is, to say the least, missing the woods for the trees at best and a red herring at worst.