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| Pressure break frequence relationship and data |
 Posted by: Dragan Savic (Dragan Savic), Fri Nov 30, 2007 2:44 pm |
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Dear all,
Can anyone help with the request below.
Regards,
Dragan
From: Julian Thornton [mailto:thornton@water-audit.com]
Sent: 30 November 2007 13:28
To: Savic, Dragan
Dragan,
Further to our discussion this morning I am sending you this e-mail to summarize the kind of data we need to find in order for us to make some conclusive steps forward on the pressure break frequency issue and the sustainability of reduction issue we discussed. The work of the IWA task force pressure management team has made some initial steps in showing that utilities with high initial break frequencies are likely to see reductions even with reasonably small reductions in maximum pressure. (article attached) This has recently been further backed up by work I have been doing here in Sao Paulo. However a question which remains to be challenged is that of the sustainability of that reduction over time given the continuing impact of the other variables which are also responsible for the high break frequency. Some of those variables might include; diameter, material, traffic loading, backfill, installation quality, materials quality and finished water temperature changes among others.
The sustainability issue is an important one as it dictates whether or not a utility should include the short term benefit of reduced maintenance cost for leak detection and leak repair and the longer term benefit of reduced frequency of infrastructure replacement into the cost benefit analysis for a potential pressure management scheme or whether the utility should only calculate the benefit from the volume of water to be saved. In the later case there may not always be much saving as the scheme may be installed to stabilize pressure not reduce it – however the question of sustainable reduced break frequency for certain components of the system could either make or break the case for installation of the scheme in this case. Other cases of course will be easily justified from the volume savings and the infrastructure savings will just be a plus.
From the data we have managed to find so far we have found that there is a wide variation of break frequency on mains of different diameters even within the same utility ranging from 50 breaks per thousand kilometers to over 700 breaks per thousand kilometers, this is also true for different pipe materials. The same is true for service breaks ranging from 2.2 breaks per thousand to over 60 breaks per thousand services.
We need to be able to collect basic water balance data plus flow and pressure logged data and GIS data (including pipe materials, lengths, service connections and materials, elevations) for a series of zones representing the range of break frequencies found in our initial research, we need to have a basic component analysis done for each zone so we understand the components which are failing and why before a change in pressure is made and then the same after. We then need to identify changes in break frequency for the different components and we need to log this over a period of time after the change in pressure regime. We will need to identify locations where pressure should be logged based on the component analysis of where the failures are occurring. Additionally if we are able to collect finished water temperature data, soil data and traffic loading data that would be very useful.
I have copied this e-mail to a few other practitioners who are dealing with these issues in one form or another and will start to send this out to others in the hope that we might be able to find some utilities who even if they do not have the data available as we need it now might be interested in working with us to put together the data and analysis over the coming months.
All the best…Julian
_________________
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Dragan Savic
Centre for Water Systems
University of Exeter
North Park Road
Exeter, EX4 4QF, UK
TEL: +44 (0)1392 263637
MOB: +44 (0)7739 552366
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