ReportNo WSAA 40
Theaim of this study was to determine the minimum household water pressure whichwas acceptable to the community. It consisted of two separate phases.
Theresults of the surveys showed that the community considered the service of theprovision of good water supply to be most important when compared with othergovernment services – even more important than the provision of hospitals.However, the provision of good water pressure was considered to be leastimportant of the services provided by the Water Authority.
Whenthe need for the provision of service for water pressure was measured using asubjective social indicator, the community considered that the service was‘about right’. However, the scores for the low pressure region did show asignificantly higher need for service than did those for the medium and highpressure regions.
Whencurrent water pressures were compared with preferred pressures and minimumacceptable pressures for various indoor and outdoor appliances, it was foundthat, in general people will accept lowerpressures for all appliances. However, the low pressure people weresignificantly less likely to accept lower pressure for most indoor appliances.Of interest though, was that the low pressure households were willing, like themedium and high pressure regions, to accept lower pressures for outdoor gardenirrigation. When preferred pressures were examined, overall people would like better pressure for allappliances but particularly so for outdoor sprinkler and reticulationsystems.
Therespondents were more inclined to notice daily pressure variations in summerrather than other times of the year and at the time of peak use each day.However, even in summer, less than half the sample noticed any variations.
Anumber of analyses were conducted to ascertain what determined satisfactionwith pressure. It was found that attitudinal items were almost as important asabsolute pressure in governing people’s overall satisfaction. Applianceownership and demographic items bore almost no relationship to satisfaction.The major attitudinal item which determines satisfaction was whether peoplewere generally happy with the Water Authority. Those not happy with theAuthority were less likely to be satisfied with their pressure (whether theirpressures were low, medium or high). These people were also more likely to bedissatisfied with water quality and the pricing structure. It would seem fromthis and previous research that the water utility’s “image” is highly linked tocustomer satisfaction.
Thesample’s absolute pressures were split into groups of five metre ranges to seeif there was a cut-off point below which pressure could be said to beunsatisfactory. It was found that pressure below 30 metres was generallyunacceptable. There was some doubt about pressures up to 44 metres. People withpressures above 79 metres were also dissatisfied.
Theparticipants in the experimental and control groups were asked to complete 2diaries each week. The diaries were used to record their perceptions of waterpressure change, the direction of change, their satisfaction with waterpressure, and what effects the perceived change had on their activities aroundthe house.
Theresults of participant awareness of change did mirror the induced pressurechanges. During the period when the experimental group’s pressure was normal,their perceptions of change was similar to the control groups. During theperiods when the experimental group’s pressure was reduced, the reporting ofchanges increased. Approximately 35%-40% of the experimental group reportedthat their water pressure had changed. The reporting of changes in pressure wasleast in the second intervention period, when the magnitude of change was infact greatest. This appears to indicate that there was an accommodation to thechanges in pressure. That is, fewer people seemed to recognise change as timewent on. This implies that people are notwell aware of their water pressure and have difficulty identifying when it isreduced. This was reinforced by the observation that approximately 15% ofthe control group identified that their pressure had changed, although noreduction was made by the experimenters.
Whenawareness of change was examined separately for the low, medium and highregions, the differences between the experimental and control groups becameless obvious. The low and high pressure experimental groups showed greatestawareness of change to pressure levels, while the medium and high pressurecontrol groups reported little change. The medium experimental group showedsome awareness of change, but less so than the high and low experimentalgroups. Interestingly, the low controlgroup reported as much “awareness” of change as the medium experimental group.Thus perceived awareness is somewhat related to the actual change in pressure,but is also related to the base pressure level.
Ineach region, there were three magnitudes of change. Magnitude of change wasmarginally related to awareness. Householders with the largest reductionsreported most change, followed by moderate and those with the lowest magnitudeof reduction reported least awareness of change. Again, there is a clearreduction of awareness over time. The levels of reported change at the end ofthe study had reduced to almost half of the initial level.
Theparticipants’ levels of satisfaction with their water pressure was recordedtwice each week during the study. The overall results showed that generally people were not dissatisfiedwith their pressure, although there were considerable variations in opinions.During the periods when the pressure was reduced for the experimental group,there were increased levels of dissatisfaction. This dissatisfaction wasgreatest during the second intervention period, when change was greatest.
Theambient temperature was found to have an effect on the level ofdissatisfaction. As the temperature went up so did the levels of reporteddissatisfaction.
Themedium experimental and control groups showed least differences insatisfaction. The high pressure groups showed greatest differentiation,especially during the second intervention period, when the reductions inpressure were greatest. The low pressure group showed most dissatisfactionoverall. While the control group was more satisfied than the experimentalgroup, they were still more dissatisfied than all other groups.
Inthe high pressure region, there were effects for the magnitude of change, butin the other regions, the patterns were more confused. Awareness of change wasalso related to satisfaction. Those who reported they were aware of change wasalso related to satisfaction. Those who reported they were aware of change wereless mistakenly reported change.
Therewas considerable consistency in people’s ratings. Thus it appears that peopledo not change their levels of satisfaction capriciously.
Household Plumbing Hydraulics
Throughthe measurement of flows and pressures at strategic points of householdplumbing it could be concluded that:
Atypical household plumbing system was modelled using the computer modellingpackage WATSYS to identify and investigate pressure problem areas in theplumbing system and to determine possible solutions. It was found that thetotal friction head loss through the service connection is very large. Thelarge head loss components are the ferrule tap on the main and the stop tap atthe water meter.
Themajor problem highlighted from these analyses is that if the mains pressure is15 metres and there are two taps “on” in the house, then the pressures in theplumbing system in the house reduce to approximately 0-5 metres with onlyminimal flows (ie. less than 0.2 litres/sec per tap).
Twoareas for improvement were identified. The Water Authority of WesternAustralia’s recently developed new water service arrangement has considerablehydraulic advantages over the old service connection arrangement. Secondly,increase the diameter of internal pipes (eg. from 15mm to 20mm and from 20mm to25mm).
Peopleare generally satisfied with their pressure. The general level of waterpressure is the greatest determinant of satisfaction. Changes in water pressureare not recognised easily, and the effects of the changes are evident, but notas dramatic as the effect of the baseline pressure. The magnitude of the changedoes not have a large influence on people’s satisfaction with the service.Ambient temperature was seen to have a moderating effect. While awareness ofchanges in water pressure levels was related to reported satisfaction, overall,there was a contra indication in that while dissatisfaction increased duringthe course of the study, awareness decreased.
Thereforeit was concluded from examination of the attitudinal, psychophysical andmodelling data that pressures of 30 metres or more should prove to besatisfactory for the average household. If the plumbing changes suggested inthis report are adopted, a lower pressure may be considered. It must beemphasised however, that there are large individual differences in expectationsof pressure and that this study was conducted with relatively new housing.Desired pressure levels may vary if the condition of plumbing has deteriorated.
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