Community Analysis of Household Water Pressure Satisfaction
This report was produced for the Urban Water Research Association of Australia, a now discontinued research program.
Report No UWRAA 105
The aim of this study was to determine the minimum household water pressure which was acceptable to the community. It consisted of two separate phases.
1. Three community questionnaire surveys were conducted pre-summer; post-summer and winter. These surveys repeatedly measured attitudes to water supply issues in general as well as water pressure specifically. The whole of the phase 2 sample participated in the first survey and a proportion in the winter survey. A further total of 655 randomly selected participants responded to some or all of the questionnaires.
2. A psychophysical experiment where ninety-four urban household participants were recruited in each of three pressure regions – a total of 282 households. Four households in each region had their water pressures and flows intensively monitored through the installation of flow meters and data loggers at strategic points in the household plumbing. All participants were informed that their pressures may be altered at any time over the study period but a control group in each region did not have any changes. Each household in the experimental group had a baseline period of no change against which satisfaction after pressure modification could be compared. Twice weekly diaries were completed over the twelve week study period.
The results of the surveys showed that the community considered the service of the provision of good water supply to be most important when compared with other government services – even more important than the provision of hospitals. However, the provision of good water pressure was considered to be least important of the services provided by the Water Authority.
When the need for the provision of service for water pressure was measured using a subjective social indicator, the community considered that the service was ‘about right’. However, the scores for the low pressure region did show a significantly higher need for service than did those for the medium and high pressure regions.
When current water pressures were compared with preferred pressures and minimum acceptable pressures for various indoor and outdoor appliances, it was found that, in general people will accept lower pressures for all appliances. However, the low pressure people were significantly less likely to accept lower pressure for most indoor appliances. Of interest though, was that the low pressure households were willing, like the medium and high pressure regions, to accept lower pressures for outdoor garden irrigation. When preferred pressures were examined, overall people would like better pressure for all appliances but particularly so for outdoor sprinkler and reticulation systems.
The respondents were more inclined to notice daily pressure variations in summer rather 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.
A number of analyses were conducted to ascertain what determined satisfaction with pressure. It was found that attitudinal items were almost as important as absolute pressure in governing people’s overall satisfaction. Appliance ownership and demographic items bore almost no relationship to satisfaction. The major attitudinal item which determines satisfaction was whether people were generally happy with the Water Authority. Those not happy with the Authority were less likely to be satisfied with their pressure (whether their pressures were low, medium or high). These people were also more likely to be dissatisfied with water quality and the pricing structure. It would seem from this and previous research that the water utility’s “image” is highly linked to customer satisfaction.
The sample’s absolute pressures were split into groups of five metre ranges to see if there was a cut-off point below which pressure could be said to be unsatisfactory. It was found that pressure below 30 metres was generally unacceptable. There was some doubt about pressures up to 44 metres. People with pressures above 79 metres were also dissatisfied.
The participants in the experimental and control groups were asked to complete 2diaries each week. The diaries were used to record their perceptions of water pressure change, the direction of change, their satisfaction with water pressure, and what effects the perceived change had on their activities around the house.
The results of participant awareness of change did mirror the induced pressure changes. During the period when the experimental group’s pressure was normal, their perceptions of change was similar to the control groups. During the periods when the experimental group’s pressure was reduced, the reporting of changes increased. Approximately 35%-40% of the experimental group reported that their water pressure had changed. The reporting of changes in pressure was least in the second intervention period, when the magnitude of change was in fact greatest. This appears to indicate that there was an accommodation to the changes in pressure. That is, fewer people seemed to recognise change as time went on. This implies that people are not well aware of their water pressure and have difficulty identifying when it is reduced. This was reinforced by the observation that approximately 15% of the control group identified that their pressure had changed, although no reduction was made by the experimenters.
When awareness of change was examined separately for the low, medium and high regions, the differences between the experimental and control groups became less obvious. The low and high pressure experimental groups showed greatest awareness of change to pressure levels, while the medium and high pressure control groups reported little change. The medium experimental group showed some awareness of change, but less so than the high and low experimental groups. Interestingly, the low control group 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.
In each region, there were three magnitudes of change. Magnitude of change was marginally related to awareness. Householders with the largest reductions reported most change, followed by moderate and those with the lowest magnitude of reduction reported least awareness of change. Again, there is a clear reduction of awareness over time. The levels of reported change at the end of the study had reduced to almost half of the initial level.
The participants’ levels of satisfaction with their water pressure was recorded twice each week during the study. The overall results showed that generally people were not dissatisfied with 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 was greatest during the second intervention period, when change was greatest.
The ambient temperature was found to have an effect on the level of dissatisfaction. As the temperature went up so did the levels of reported dissatisfaction.
The medium experimental and control groups showed least differences in satisfaction. The high pressure groups showed greatest differentiation, especially during the second intervention period, when the reductions in pressure were greatest. The low pressure group showed most dissatisfaction overall. While the control group was more satisfied than the experimental group, they were still more dissatisfied than all other groups.
In the high pressure region, there were effects for the magnitude of change, but in the other regions, the patterns were more confused. Awareness of change was also related to satisfaction. Those who reported they were aware of change was also related to satisfaction. Those who reported they were aware of change were less mistakenly reported change.
There was considerable consistency in people’s ratings. Thus it appears that people do not change their levels of satisfaction capriciously.
Household Plumbing Hydraulics
Through the measurement of flows and pressures at strategic points of household plumbing it could be concluded that:
- The parameters that affect quantity of water available are the Water Authority’s main’s pressure, service connection type and automatic reticulation or sprinkler off tap;
- Even if the mains pressure is low (i.e. less than 30 metres head) and the house has automatic reticulation (used at non-peak periods), large waterflows can be obtained. Houses without automatic reticulation, that is just one sprinkler operating off a tap, have much smaller flows.
A typical household plumbing system was modelled using the computer modelling package WATSYS to identify and investigate pressure problem areas in the plumbing system and to determine possible solutions. It was found that the total friction head loss through the service connection is very large. The large head loss components are the ferrule tap on the main and the stop tap at the water meter.
The major problem highlighted from these analyses is that if the mains pressure is 15 metres and there are two taps “on” in the house, then the pressures in the plumbing system in the house reduce to approximately 0-5 metres with only minimal flows (i.e. less than 0.2 litres/sec per tap).
Two areas for improvement were identified. The Water Authority of Western Australia’s recently developed new water service arrangement has considerable hydraulic advantages over the old service connection arrangement. Secondly, increase the diameter of internal pipes (eg. from 15mm to 20mm and from 20mm to 25mm).
People are generally satisfied with their pressure. The general level of water pressure is the greatest determinant of satisfaction. Changes in water pressure are not recognised easily, and the effects of the changes are evident, but not as dramatic as the effect of the baseline pressure. The magnitude of the change does not have a large influence on people’s satisfaction with the service. Ambient temperature was seen to have a moderating effect. While awareness of changes in water pressure levels was related to reported satisfaction, overall, there was a contra indication in that while dissatisfaction increased during the course of the study, awareness decreased.
Therefore, it was concluded from examination of the attitudinal, psychophysical and modelling data, that pressures of 30 metres or more should prove to be satisfactory for the average household. If the plumbing changes suggested in this report are adopted, a lower pressure may be considered. It must be emphasised however, that there are large individual differences in expectations of pressure and that this study was conducted with relatively new housing. Desired pressure levels may vary if the condition of plumbing has deteriorated.