On the trail of a blocked pipe

2011-12-05 00:00

THEFT of manhole covers and even the plumbers’ tools were behind the recent three-day water outage that affected large parts of Pietermaritzburg.

The detection and solving of the problem had all the elements of high drama and in the end it was the ear of experience that solved the baffling problem.

Acting water superintendent Mike Khubeka’s 30 years of service in the Msunduzi water section had him attuned to the different sounds of water flowing through pipes. What he heard convinced him there was something wrong.

It all started early on Thursday morning, November 24, in the control room of the water department. Staff monitoring the telemetry system that records water levels in the city’s reservoirs, noted a significant drop in the outflow in the bulk water system serving parts of Northdale, Panorama, Copesville, Eastwood, Glenwood, Bishopstowe, Mountain Rise, Willowton and ultimately sections of Hayfields.

The system is served by a main reservoir in Otto’s Bluff and feeds into a series of five sub-reservoirs. As staff set out to look for leaks, household taps began drying up and the first of thousands of irate calls were made to the municipality.

As they were scouting the area, a mid-morning downpour put paid to their efforts to visually detect a burst.

With Friday dawning clear, the team set off walking the seven-kilometre distance between the main reservoir and the smaller Copesville one. Along the way they opened valves, scoured the lines and checked the pressures.

By 4 pm on Friday the problem had been isolated to the Copesville reservoir site. This meant that each of 14 large valves needed to be dug up and checked for malfunctioning, a process that could take three to four hours on each valve.

Work started on the first valve on Friday evening, but operations had to be stopped at 2 am when the team’s plumbing tools were stolen from their vans. These were parked near the road at the Copesville Reservoir on Mattison Drive. The police had to be called and the theft was reported.

Work started again early on Saturday with replaced and borrowed tools. The second valve was taken apart, all appeared in order and it was put back together again.

As water began flowing back into the chamber Khubeka said: “the water flow does not sound right”.

The city’s acting process manager for water and sanitation, water engineer Brenden Sivparsad, takes up the story:

“We started cutting, digging up a section of the pipe and with the use of a cellphone we took photographs inside.

“There was something stuck in what we call an orifice plate, which is smaller and is used to build pressure in the system.”

They tried pushing a rod through to pull out the obstruction. This did not work. By this time it was 3.30 pm on Saturday afternoon.

More excavation followed and a further section of the pipe was cut open to pull out what turned out to be a five litre plastic container.

An everyday object had caused half of Pietermaritzburg to go without water. Sivparsad said manhole covers are continuously being vandalised and stolen. “We have to check every day. The container could have fallen in when a cover was stolen.”

He is in the process of motivating for 24-hour security for the reservoirs.

Water quality was not affected. According to Sivparsad, any contamination would have been detected by a routine monitoring programme, which is a key competence that has to be carried out by Msunduzi Municipality as part of retaining its Blue Drop status.

The system is also thoroughly flushed via fire hydrants and scour valves before it is allowed to reach consumers.

Sivparsad said reopening the system takes hours. In this case the pipes needed to be welded back, valves re-opened slowly and the system flushed clean.

Water is also released in slowly from the main reservoir to prevent air from compressing in the pipes causing bursts. The system was in full operational by 3 am on Sunday, November 27. Sivparsad paid tribute to the entire team who worked non-stop.

He thanked the business community in Willowton for their offers of help and residents for their understanding and patience.

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