Improving access to urban piped drinking water services in Africa: a scoping review

The importance of access to reliable and safe drinking water of sufficient quantity to meet the needs of personal and household hygiene for public health is well established (Wolf et al. 2022). The recognition of the importance of access to water supply has been reflected in a number of key global commitments from the Alma-Ata Declaration in 1978 (World Health Organization 1978), through the Water Decade of the 1980s, the Millennium Development Goals (Bartram et al. 2014) and now the Sustainable Development Goals (SDGs) (UNGA 2015). Yet, despite these commitments, progress remains limited with about 2.2 billion people continuing to lack access to a safely managed water supply, and over 400 million people with no access to some form of improved water supply (WHO & UNICEF 2021). In Sub-Saharan Africa, 35% of the population lack access to a basic water supply, with no regional statistics available for access to safely managed water supply (WHO & UNICEF 2021).

The type of water supply delivered and the level of service provided is known to affect the degree to which health, social, and other benefits are realised (Wolf et al. 2023). Provision of piped water, particularly when this is to the residence (either through a single tap or multiple taps) offers the highest potential level of service and one which should be considered as the preferred option (Howard et al. 2020b). Such levels of supply are best suited to meeting personal and household hygiene needs, including during periods when enhanced handwashing is required such as the COVID-19 pandemic (Howard et al. 2020a). When properly operated by utilities, piped water offers the greatest potential for safety management and independent regulation. In urban areas the provision of piped water supply is always preferred because quality can be better assured, and higher population density creates economies of scale that reduces the unit costs of service delivery (World Bank 2017c).

Current global monitoring data shows that improved water supply at the residence (which includes both piped and non-piped water sources) lags behind overall measures of access to water supply (WHO & UNICEF 2021). Rates of access to an improved supply in Sub-Saharan Africa fall below global averages (WHO & UNICEF 2021). Expansion of water supplies has failed to keep up with demands, particularly in informal urban settlements (Tumwebaze et al. 2023), leaving a billion people living in urban slums without access to water supplies (Satterthwaite et al. 2020). Previous studies have suggested that access to piped water actually declined between the 1990s and early 2000s (Banerjee et al. 2008). Data from the WHO/UNICEF Joint Monitoring Programme (JMP) portal further demonstrates that access to piped water in urban areas of Sub-Saharan Africa has decreased from 65% of the population in 2000 to 58% in 2022 (WHO/UNICEF 2024). Population growth, rapid urbanisation, poor governance, and reductions in investment all contribute to this declining access (Dos Santos et al. 2017). Moreover, in the last decade, economic progress across Sub-Saharan Africa has grown at a slow pace from $1,646/capita in 2010 to $1,701/capita in 2022, equating to an average growth rate of 3.3% (World Bank 2024a, b). The low economic starting point and limited growth is likely to have constrained levels of investment in public services, including expansion of access to piped water supply. For comparison, equivalent rates for South Asia, the European Union and North America were 79.8%, 13.7%, and 54.4%, respectively (World Bank 2024a, b). The effects of climate change and ongoing economic inequalities will also influence the degree to which universal access to at-residence piped water supply will be achieved in Sub-Saharan Africa (Dos Santos et al. 2017; Armah et al. 2018).

In addition to the macro-constraints highlighted above, there are constraints at the household level that have inhibited uptake of connections where the infrastructure exists. Notably, the upfront capital cost of acquiring a connection has been identified as a substantial barrier for poorer households (Kayaga & Franceys 2007), and the billing-cycles that most utilities employ is at odds with income patterns of the poor, preventing them taking up household connections even though the total annual cost is affordable (Michaels et al. 2022). Furthermore, many households that do connect to piped water supplies experience intermittence in supply, which at times results in multiple source use and increased risks to health caused by consumption of contaminated drinking water (Daly et al. 2021).

Despite this gloomy prognosis, there has been substantial investment in piped water supplies across Africa involving both expansion of infrastructure and the use of economic instruments that encourage uptake of household connections (Armstrong et al. 2022). There have also been efforts to increase quality of service by increasing the number of hours per day and days per week that water is supplied (World Bank 2016). Many governments on the African continent have targets for universal access to at-residence piped water, for example Kenya's National Water Master Plan 2030 (Republic of Kenya Water Resources Management Authority 2013). However, these experiences and programmes remain dispersed in the literature. We therefore embarked on a review to consolidate the lessons that have emerged, and to provide evidence on approaches that have led to sustained improvement in access to piped water across urban settings in Africa.

The aim of this review was to provide a comprehensive assessment of the progress made in increasing access to piped water supply in urban areas of Africa by undertaking a robust review of the peer-reviewed and non-peer-reviewed literature.

The specific research questions framing the review were:

1. What is the evidence that programmes reported on have successfully increased the number of piped water access points to towns or cities in Africa?

2. What is the evidence that programmes reported on have successfully increased the level of service (i.e. hours of supply, reliability) of piped water access in towns or cities in Africa?

3. What is the evidence that the type of programme implemented (infrastructure expansion, economic instrument) has influenced its success?

4. What influence have national and international targets had on the success and size of programmes?

5. What is the evidence that programme outcomes have been sustained over time and have further outcomes been reported?

This review was designed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) (Moher et al. 2009). Screening was performed by authors S.L.W., A.N., and O.R. Where there was disagreement on whether a paper should be included, this was resolved via discussion with an independent reviewer (G.H.). Full-text review was undertaken by S.L.W.

Potentially relevant peer-reviewed literature was extracted from the Scopus, Web of Science and PubMed databases in April 2023. The structured keyword search contained terms grouped into themes of drinking water, piped networks, and African countries. No restrictions were placed on date of publication or location of the keywords in the paper. However, non-relevant subject categories were excluded (such as dentistry and nuclear science), and only research articles published in English and French were accepted for consideration.

Given the legacy of investment by multilateral and bilateral donors, and philanthropic funders in water supply programmes in Africa, potentially relevant literature was sourced from online resources of the African Development Bank (AfDB), the World Bank, and IRC Library. Within each, the phrase ‘piped drinking water’ was searched and results limited to African countries. Author SLW performed a full-text review for each resulting report. A final set of 53 reports (14 from the AfDB, 38 from the World Bank, and 1 from the IRC Library) were identified for this review. Within this paper, the reports identified will be referred to as ‘grey’ literature, meaning that the reports may have not been externally peer-reviewed.

Relevant data were extracted for eligible projects identified through the peer-reviewed and grey literature searches. For each project, data were extracted around three themes: project information (e.g. location, cost, funder, dates), intervention details (e.g. type, pro-poor approach, changes to supply), and any outcomes (e.g. improvements to access, water quality changes, socio-health outcomes). Additional information on system deterioration or if the improvements to access were not sustained was noted. Given the heterogeneity of the studies, a meta-analysis of the data was not performed and analysis was limited to a narrative synthesis. As this was a scoping review and given the high number of grey literature reports consulted, a quality appraisal was not conducted, in line with guidance on scoping reviews (Munn et al. 2018).

The primary outcome of the expansion interventions was the increased number of connections to the piped water system at the household and/or community level. Installation or rehabilitation of household connections and community standpipes/kiosks were reported by 53 (82%) and 32 (49%) projects, respectively. Six projects did not specify what type of connection was utilised. Projects reported the number of connections provided, the number of consumers benefitting, or both, as seen in the Supplementary Material, Table S1. Often, the exact number of beneficiaries was unknown, so estimates were made given a standard household size. The number of increased connections and beneficiaries scaled with the scope and cost of the project. For example, the Water and Sanitation Service Improvement Project funded by the World Bank from 2007 to 2019 significantly increased access across many areas of Kenya (World Bank 2020). The reported 65,000 new household connections and 1,195 constructed or rehabilitated community water points were estimated to benefit 2,427,200 people.

A secondary outcome of some expansion projects was to provide an improved service. In these cases, an improved service constituted greater hours of supply, higher pressures and/or reliability (meeting expectations of supply frequencies). A quarter of projects (17, 26%) conveyed improvements in service, but typically in generalised terms. Higher pressures and reliability were referred to in one and five projects, respectively, but without any specific information or measurements. The report detailing the Kaduna Water Supply Project in Nigeria, for example, stated ‘the level of service in Kaduna City has manifestly improved… but the lack of reliable indicators prevents quantifying this improvement’ (World Bank 1990). In cases where hours of supply changed (six projects), those changes were quantified; for example, in Pemba, Mozambique, the Second Water Services and Institutional Support Project was able to more than double the previous 6 h of supply per day to 14 h of supply per day (World Bank 2016). Three projects in Ghana, Mauritius, and Niger fully transitioned the piped network from intermittent to continuous ‘24/7’ supply (African Development Bank Group 1988; World Bank 2011, 2017a).

Nevertheless, three physical intervention projects saw a negative change in service, described below. Each was included in the peer-reviewed literature and attributed the negative change to utility management and external events. Despite the construction of a large reservoir and expansion of the distribution system, the quality of service in a project in Uvira, Democratic Republic of the Congo, worsened in many places due to limited water production capacity, major flooding events and persistent electrical supply issues (Gaiffe et al. 2023). In Maputo, Mozambique, average supply following the 2008–2014 intervention was boosted from 10 to 17 h/d (i.e. initially improved). However, supply reduced to 12 h/day in 2016 due to increased demand from the new connections, then reduced again in 2017 due to a regional drought (Kinghan et al. 2018). Whilst overall coverage was expanded in Wa, Ghana, maintenance and ongoing network expansion by the utility, coupled with heightened water-bill delinquency, led to intermittent disruptions to existing connections (Dakyaga 2022).

Most of the interventions (59, 94%) were centred on the construction or rehabilitation of physical components, such as treatment works, storage reservoirs, and distribution systems. These physical expansion programmes ranged substantially in scale and cost, as outlined in the Supplementary Material, Table S1. The lowest-cost project took place in the town of Gazer, Ethiopia, in 2020 at a cost of $4,000 (Mussa 2020). Here, a limited water supply service that had not met growing demand led to a community-led initiative to expand the network to include two additional water sources, pipelines and 181 new household connections. At the other end, the highest-cost project took place in Algeria between 1984 and 1989 (World Bank 1987b). Titled the ‘Second National Water Supply and Sewerage Project’, the World Bank funded the expansion of three large urban water supply projects in Greater Algiers, Oran, and Constantine, as well as eight regional projects in seven provinces. At the time, the programme cost $585 million (equivalent to $1,644 million today) and aimed to provide household water connections to 750,000 people and overcome water shortages.

Where the physical intervention was the sole focus (54 projects), 24 projects targeted improving access to the urban poor. Yet, the scope of the interventions varied greatly. The physical expansion in ten projects was specifically designed to incorporate connecting households in low-income communities. Here, the phrase ‘social connection program’ was commonly utilised to describe the intervention. For example, introduction of a social house connection program meant that approximately 40% of physical expansion in the cities of Douala and Yaounde (Cameroon) was performed in low-income areas (World Bank 1979). One project had a unique objective where a piped water network was constructed in a refugee camp setting in Tindouf, Algeria (García et al. 2021). Ongoing conflict necessitated a semi-permanent water supply solution as the refugee camp expanded and became more established as an urban centre. Emergency water trucks were gradually replaced by a pipeline network between 2001 and 2005. In contrast, the other 14 physical intervention projects had limited social impact as improving access to the urban poor was a supplementary objective. Projects typically focused on building community standpipes in order to most effectively serve densely populated neighbourhoods. Overall, the number of reported urban poor beneficiaries from projects providing physical interventions was considerably smaller than those residing in higher-income areas.

Eleven projects employed a financial approach to expand water supply access, either as the sole focus of the intervention (six projects) or as part of a physical intervention (five projects). Financial interventions consisted of subsidies, grants and micro-financed loans, which were made available to consumers. In all cases, low-income areas, where existing connection costs are prohibitive, were targeted. As an example, the World Bank's Global Partnership on Output-Based Aid funded a project (2014–2017) to increase piped water connections in low-income areas of Nairobi, Kenya (The Global Partnership on Output-Based Aid 2012b). Subsidised connections at a cost of $4 to the household and $80 to the funder (40% of total connection cost) led to 16,000 households gaining piped water supply for the first time. Half of the fee was due on independent verification of a working connection and the remaining half due after six months of sustained service delivery.

Each of the financial interventions, such as the value of subsidies and loan repay conditions, was unique and adapted to the specific setting. Table 1 summarises how projects were implemented (e.g. subsidy, loan, grant) and what was included for consumers (e.g. connection fee and materials), where this information was clearly stated in the text of identified studies. Subsidies and loan-repayment mechanisms were commonly utilised as well as reduced connection-fees. These interventions did increase the number of urban poor accessing the water distribution system for the first time. However, challenges did arise. Kinghan et al. reflected that only approximately 8% of the targeted urban poor in Maputo, Mozambique, were aware of the option to pay the connection-fee in instalments (Kinghan et al. 2018). Despite a material subsidy tool in Kampala, Uganda, which provided free connection-materials for the first 50–60 m from the distribution system, Murungi and Blokland noted that ‘the remaining length and related materials charges are too high for the poor thus limiting them to benefit’ (Murungi & Blokland 2016).

To understand the motivating environment for interventions, data were extracted relating to their expressed origin. Driving factors ranged from local challenges to national aspirations. Three projects in the Democratic Republic of Congo, Guinea and Zimbabwe specifically cited recent outbreaks of cholera and Ebola as urgent drivers of change (World Bank 2017b; Cole et al. 2021; Gaiffe et al. 2023). In contrast, a project in Senegal was borne from the country's ambition to become an emerging middle-income country (World Bank 2015). Specific national policies and development plans were referred to, such as the Government of Kenya's Vision 2030 and the Government of Uganda's policy to provide safe drinking water to all by 2030. Despite the highly variable particulars, common themes emerged: (1) increase current access and affordability, (2) prepare for rapidly accelerating growth, (3) sustainable development of economic areas, (4) health improvement, and (5) extension of services to low-income populations.

Any organisations financially contributing to, and thus potentially determining the direction of, each intervention were identified. The World Bank and AfDB acted as funders (either solely or part of a group) on 83% and 73% of the physical and financial intervention projects, respectively. Moreover, 36% and 44% of the World Bank and AfDB projects targeted the urban poor to some extent, from construction of community standpipes to offering subsides for low-income areas.

Reflecting the aspiration to improve public health, 38 of the physical interventions (64%) included a new construction or upgrade to water treatment plants and processes. Occasional financial provisions were also made for water quality control, such as monitoring programmes, technical training, and testing laboratories. However, only 15 projects commented on changes to quality due to the intervention, described in the Supplementary Material, Table S1. Of those, seven were positive changes, seven were negative changes, and one was not investigated.

Five projects reported explicitly measuring water quality improvements. One project in Angola found that the percentage of tested water samples passing water quality tests increased from 0% to 98% by the third year (World Bank 2019b). One project in the Congo Republic reported that water quality from an extended treatment plant was constantly checked and found to be satisfactory (African Development Bank Group 1987). A project in Malawi found over 98% of samples met World Health Organization Drinking Water Quality Guidelines (African Development Bank Group 1992). A project in Mali reported 99% compliance with bacteriological and physico-chemical standards (World Bank 2013). Finally, one project in Mozambique reported that households identified issues with water colour after the construction of a rapid filtration water treatment plant, but later changes to the processes improved water clarity (Sequeira et al. 2019). Critically, none of these projects explicitly stated what parameters were being tested for nor provided the reported values.

Four projects attributed negative water-quality changes to poor treatment management. In Egypt, one project reported that filtration plants were operated at higher than design rates (World Bank 1987a). A project in Lesotho reported that chlorination and pH control were not in use (African Development Bank Group 1986). The chlorine-dosing system in a project in Nigeria was reported to be considered obsolete and corrosive (African Development Bank Group 2000a). A project in Uganda reported that improper chlorine dosing continued uncorrected for years (African Development Bank Group 2000b).

Microbiological contamination was detected in two physical intervention projects: within household storage tanks in the Sahrawi refugee environment in Algeria (García et al. 2021) and across standpipes, taps and reticulation systems in the Four Centers project in Lesotho (African Development Bank Group 1999). A project in Djibouti suggested that puddles around leaking standpipes created a breeding ground for mosquitoes (African Development Bank Group 1997). No project measured health outcomes in the intervention communities. Five projects, however, stated that public health improved; for example, the Ministry of Health for Mauritius reported a ‘downward trend of [waterborne] disease’ after the 1979–1983 Port Louis intervention (African Development Bank Group 1988).

Additional outcomes resulting from the interventions were anecdotally described in the literature, but typically without any quantitative measurements. As communities became connected to the municipal distribution system, alternative water supply sources became less utilised (World Bank 2021). In Niger's Water Sector Project, the share of the population with social connections that spent more than 10% of their daily budgets on water supplies fell from 62% to 16% (World Bank 2011). Elimination of daily tanker trucks and closure of contaminated/unprotected wells contributed to a more positive environment (World Bank 1978, 2019a, b). Household connections reduced time queuing and ‘hauling’ water from sources outside the household, which was often in the literature conveyed to benefit women as disproportionate water collectors (Yap 2007; World Bank 2015). Moreover, as new connections enabled residents to obtain water within their property, prevalent ‘water conflicts’ due to scarcity of privately owned water kiosks became ‘hardly witnessed’ (Mukoya & Mwaura 2014). At the community level, positive outcomes included greater household value for those now connected to the municipal water supply, as well as a flourishing of local contractors due to the construction needs (Sequeira et al. 2019; World Bank 1995, 2020). Some utilities reported higher bill recovery and reduced unaccounted-for water (World Bank 2008; Kinghan et al. 2018), but this was not consistent across projects.

However, not all additional outcomes were positive. One project in Uganda shared that standpipes built as part of the intervention became politicised (Appelblad Fredby & Nilsson 2013). Known as ‘yellow water’ for the corresponding presidential party, the authors assert that ‘pledges of cheap and abundant water made with ulterior political motives fail to attain long-term financial sustainability’. Other adverse outcomes included higher consumption costs to subsidise new connections and serious environmental issues due to excessive siphoning (World Bank 1992).

All projects described an intervention that increased the number of community members connected to the piped drinking water distribution system. Yet, five of the 12 (42%) peer-reviewed documents and 17 of the 53 (32%) grey documents described one or more aspects of system deterioration, such as increasing non-revenue water levels, limited production capacity, and non-working equipment. Physical leakage in particular is known to be a severe challenge, and high rates can compromise the ability of suppliers to meet demand. In the Third Nairobi Water supply project, for example, the level of non-revenue water (which includes physical leakage) increased from an estimated 28%–51% post-intervention (World Bank 1998). Similarly, non-revenue water levels were contemplated to decrease from 39% to 29% in the Alexandria Water Supply project, but were heightened to >49% at the time of evaluation (World Bank 1987a). Aspects of system deterioration would imply that the intervention deteriorated to some extent after implementation. It is worth noting that these indicators are likely to have complex dependencies, therefore overlap may occur.

Table 3 shows that between a quarter and a third of physical and financial interventions described deterioration related to demand outstripping supply and insufficient utility management. Physical interventions also experienced a higher proportion of challenges related to increased non-revenue water and equipment not in proper working order. An example of this combination is the 1990–1992 expansion of the water supply system in Bauchi, Nigeria (African Development Bank Group 2000a). The report states that, due to a shortage of qualified and trained staff and mismanaged funds, the system suffered from ‘rampant leakage even resulting in total shutting off of supplies to some areas’. A new treatment plant considered ‘obsolete’ and ‘corrosive’ after a couple of years meant that ‘the quality of water suffers seriously’.

Within financial interventions, none reported suffering from equipment or non-revenue water losses. Yet, Appelblad Fredby and Nilsson report insufficient cost recovery and misadjusted tariffs challenges from a 2002–2009 pro-poor intervention in Kampala, Uganda (Appelblad Fredby & Nilsson 2013). They state that ‘while the connection cost has been lowered… the water tariff has been increased by an average of 10%… [therefore] a negative consequence has been the tendency of poor people getting individual connections without being able to pay for their consumption, thus being disconnected’. The authors go on to say ‘the utility has itself concluded that prices are hiked by the vendors and kiosk operators to the extent that this model is now deemed to be ineffective to reach the urban poor’.

The narrow number of studies drawn from peer-reviewed academic literature suggests that robust evaluations of projects to expand access to water supply remain limited. Furthermore, the studies available are concentrated in a small number of countries, with just two (Uganda and Mozambique) accounting for almost half of all studies. The grey literature yielded a more diverse set of countries where studies and evaluations had been undertaken, but again large numbers of countries across the continent do not report any studies on piped-water expansion and there is a concentration of studies in a handful of countries.

The limited peer-reviewed and grey literature reflects a challenge for the water sector to present and use the evidence from interventions to help inform new programmes and policies. It is clear that moving forward there needs to be greater investment in robust evaluations, with clear baselines and outcomes identified at the outset to improve the evidence base. By preference, more evaluations subject to anonymous peer review should be encouraged. It is unlikely that there have been no programmes to expand piped water in those countries where papers or reports could not be identified, thus suggesting there remains a lack of rigorous assessment of intervention effectiveness. The concentration of academic papers in only nine countries, with half the papers addressing only two countries, also suggests that there may be publication bias and as a consequence, some caution may be needed in interpreting the findings of published studies. The studies identified overwhelmingly report on physical interventions concerned with extended availability and accessibility of infrastructure to provide drinking water. While this may be understandable in a continent with a known deficit in water supply infrastructure, such a focus is at odds with studies that have identified economic and/or financial barriers to uptake of household connections such as upfront costs to households of acquiring a connection, billing-cycles that conflict with income patterns, and unaffordable water tariffs (Kayaga & Franceys 2007; Adams & Vásquez 2019). While some of the studies did attempt to integrate actions such as subsidised connections, the apparent principal focus on infrastructure expansion may well explain why high-income households benefited more than low-income ones. This is despite nearly 60% of the studies noting that the projects were designed to target poor communities and that funding came from development banks and large INGOs whose mission is to alleviate poverty.

This analysis suggests that, while physical expansion of piped networks may be required to cope with rapidly expanding populations and physical growth of cities, there must be a stronger focus on economic instruments and social protection if expanded supplies are to truly benefit the poor. This would seem therefore to call for new project designs and greater transparency and accountability in utilities and funders of water projects. Given that Africa continues to lag substantially behind meeting the SDG 6.1 target (UNICEF & WHO 2023) and the noted importance of piped water supplies during the COVID pandemic (Howard et al. 2020a), this calls for more balanced project design and much greater emphasis on accessibility as well as availability. Furthermore, the mixed evidence on how effective the programmes identified were in improving access for low-income communities suggests that there is a need to develop better models of financial interventions. The limited robust evaluations across Africa may inhibit the development of new approaches. This, therefore, reinforces the need for more rigorous evaluations, and preferably those subjected to anonymous peer review.

The increase in access reported in the literature was not always accompanied by improvements in service quality, with only one-quarter of the studies observing that service improvements resulted from expanded access. A substantial number reported deterioration in services experienced by some or all consumers. This result implies that the focus on increasing availability by expanding piped networks is not being complemented by effective improvements in utility performance management. When combined with findings that the focus of most projects has been on physical expansion with limited attention paid to financial and social barriers, this points to approaches that are infrastructure-focused rather than end-user-centred infrastructure operation that is more sustainable (Knoeri et al. 2016). This is reinforced by the unexpected adverse outcomes reported in some projects where better consideration of management and governance may have avoided problems. It is interesting that several of the studies focused on projects that aimed to improve water quality by improving water treatment and in a few cases improving water quality control. It is striking that few of these studies reported any detail of what changes were achieved and of those that did, the same number reported deterioration in water quality or water treatment failures, as those reporting improvements. Adverse outcomes such as these may well explain why the anticipated benefits are not always being realised.

A consistent theme running across projects where water quality deteriorated is poor operational management, suggesting a failure to invest in training and staff development when making large infrastructure investments. The need for such investment has been noted as urgent for the sector (IWA 2014) and is essential if water is to be safely managed (UNICEF & WHO 2023). Wider system deterioration was also reported in a surprisingly high number of studies (almost half of peer-reviewed papers and one-third of all papers). Increases in non-revenue water, limited production capacity and failures in equipment suggest a mix of poor design and, as importantly, poor operation and management, with a conclusion that many investments offer poor prospects of long-term sustainability.

The need for greater transparency and accountability is reinforced by the difficulty in determining from the reported studies exactly how many people had benefited from expansions of piped water supply, despite this being the primary outcome of most projects. There should be greater demand for more robust evidence on beneficiaries. The approach to estimate people served by calculations based on average household size may very well obscure unequal distribution of benefits.

The evidence regarding drivers for piped water interventions and especially the role of major international commitments provides interesting insights. Only a small number of the projects studied were designed in response to outbreaks of infectious waterborne disease. This suggests the drive to improve public health, while perhaps implicit in water supply planning, is not the critical driver in most cases. Other factors, such as the desire to be seen as a middle-income country, appear as likely to be explicit goals.

The Joint Monitoring Program defines safely managed water – the level of service that is compliant with the target SDG 6.1 – as: ‘Drinking water from an improved source that is accessible on premises, available when needed and free from faecal and priority chemical contamination’ (WHO & UNICEF 2017). It can therefore be expected that more investments will be made to expand piped water supplies as the most efficient way of achieving this target. The small number of studies reporting on projects initiated under the SDG period may reflect that there has been insufficient time since the start of the SDGs for the full range of studies on projects to emerge. If this is the case then there is a clear need for more reports on the success or failure of programmes, not least because this may inform new projects initiated in the remaining six years before the SDG end-date of 2030. However, the limited number of studies may also either reflect an absence of projects or limited rigorous assessment of effectiveness, both of which would be of concern given the continued slow progress in Africa towards meeting the SDG targets (UNICEF & WHO 2023).

This review was undertaken to understand the evidence of effective approaches to expanding access to piped water supplies in urban areas of Africa. It is clear from the literature that progress has been made in improving access, which is consistent with global monitoring. Yet, the limited number of studies overall and the very small number of papers in the peer-reviewed literature demonstrates an inadequate evidence base. Considering the short time left to achieve the SDGs, this is of concern. In light of the recent COVID pandemic and the ongoing need for investment in water supplies post-2030 to achieve universal access, far more rigorous studies of effective approaches to expanding access to piped water are urgently needed. The evidence from the literature points to investments that are primarily driven by infrastructure rather than being people-centred. The limited attention to addressing economic and social barriers may well explain why poor households and communities have overall benefited less than wealthier households and communities. This calls for a different approach if universal access is to be achieved. The substantial number of studies that showed deterioration in service quality suggests that more investment is also needed to improve ongoing operation and management of piped water supplies.

This work was supported by the UK Economic and Social Research Council (Grant no.: ET/T007656/1) awarded under the Global Challenges Research Fund.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.