Putting the heat on sludge

Wireless leak alarm triggers when consumption exceeds expectations

Transmitter unit sited in water meter chamber

In designing a system to tackle the problem it was recognised that pulsed meters were available and likely to be installed in increasing numbers. This made it possible to detect the flow of water through a meter, translate the pulses into a readable form and use the data to perform various functions.

Two systems were suggested, hard-wired or radio link. Both would monitor pulses from the water meter and convert them into alpha numeric form for on-screen display. The systems would connect to the output on the water meter, with the hard-wired version directly connected by a signal wire to its VDU while the radio link model would transmit the data via a radio frequency to its visual readout receiver. Both systems incorporated a dedicated microprocessor which permitted users to select the constant flow period that best reflected their demand expectations and triggered audible and visual alarms should these be exceeded. The cost of the radio link version was deemed unacceptably high and the hard-wire system was developed because it seemed, in cost terms and practicality, to fit the requirements of the farming industry. Later it became apparent this was the wrong option.

The hard-wired system became available in 1993 and functioned successfully, however little account had been taken of the practical difficulties of wiring the system to the VDU and finding a secure position for the receiver unit. The system was limited to new-build sites where signal cables could be laid while open trenches were available or sites where the unit could be mounted next to the meter chamber. Sales were slow and it became clear the radio link system was the way forward.

The electronics company which developed the system had on its own initiative been undertaking research into a radio link option. The concept had also been independently researched elsewhere and yet with another party on the scene Elimileak started to move forward.

The radio link system comprised two basic units:

• a transmitter connected to the water meter capable of operating either above ground or within the meter chamber,
• a receiver unit capable of receiving data from the transmitter via a range of receiving aerials. The functions required of the system were:
  
• meter readout updated every 15 minutes or as required,
• a range of constant flow alarm settings to suit a wide variety of water user parameters,
• audible and visual alarms if constant flow settings are exceeded,
• transmission range up to 3-5km dependant on installation circumstances,
• user screen to enable consumers to monitor usage for any period of time selected,
• high flow alarm/selectable time period for large water consumers,
• low flow alarm/selectable time period for small users for whom monitoring minimum flow is critical.

South West Water agreed to co-operate at several trial sites including a shared subsidiary office of its own. Other sites were a large Plymouth community school and a junior school. The trials proved highly successful with the system flagging previously undetected leaks at two of the sites within 24h of installation.

During the trials the need for several improvements became apparent. If the transmitter was to be installed in the meter chamber up-rating of the transmitter enclosure to an IP67 specification was essential just as the potting of all electronic components became necessary.

Following further trials South West Water approved the product as "a valuable aid to water management", and permitted connection of the system to its customers' water meters. A recent evaluation report states: "The Elimileak has several features which are not currently available with other products. The meter reading screen is a useful tool and especially suitable for schools where students can become involved in water efficiency projects and analysis. It would also be particularly suitable for commercial customers who have long service pipes and/or extensive underground plumbing."

Despite the trials, as soon as the system got on to the market new problems were encountered. It was frequently found that when the transmitter was installed in the meter chamber it was not always possible to obtain the signals at the preferred receiver position, and sometimes the transmission range was reduced to as little as 50m. This problem was solved by the development of signal repeater units. When installed near the transmission point the units relay the signals to the receiver, using repeaters in a chain permitted almost limitless transmission distances.

One customer wanted to link the system to a Building Management System (BMS) which led to the creation of the Elimileak BMS interface unit. A unit capable of monitoring combined meters was installed at the Exeter headquarters of Devon County Council where it has been operating for more than 18 months. Commenting on the system the council's principal strategy and energy engineer, said: "this instrument allows us to conveniently monitor our water consumption daily and more importantly alarms us of any excessive consumption/leak."

The system has proved conclusively that the scale of leakage or wasteful usage for which the consumer is responsible is greater than statistics currently indicate. This was best demonstrated by a contract awarded by Plymouth City Council for 26 installations at schools. In all, 15 were found to have leaks of which the schools were completely unaware. Since installation virtually all the sites have reported the systems have flagged leakage/wasteful usage. This has enabled early remedial action, reducing further wastage and ensuring lower water bills. Referring to a schools water conservation initiative, a Cornwall County Council report concluded: "The system has certainly raised the awareness of the value that can be gained of improved water management this even in some cases extends to the teaching staff as well, this added benefit is attributed simply to the ease with which monitoring can now be carried out. The existing leaks that were detected immediately following installation of the system only confirmed what we had previously suspected but been unable to prove and justified fully the cost of both contracts that have been awarded."

During the past three years those involved in Elimileak have seen commercial water consumers taking an increasing interest in water management and as a result the difficulties and inconvenience of carrying out frequent meter checks are being recognised. The reliance on meters alone for water management purposes is increasingly being questioned and new products are being demanded.