Introduction Unsafe water, sanitation and hygiene (WASH) causes millions of deaths and disability-adjusted life-years annually. Despite global progress towards universal WASH, much of WASH programming continues to fail to improve health outcomes or be sustainable in the longer term, consistently falling short of internal performance indicators and sometimes negatively impacting the well-being of local stakeholders. Although sector experts in high-income countries have often provided explanations for such failures, the opinions of those implementing WASH programming at the ground level are rarely published.

Methods In 2020, we purposively recruited 108 front-line WASH professionals in Malawi, South Africa, Tanzania and Zimbabwe to participate in 96 in-depth interviews, explaining why they believe WASH failure persists. Through participatory analysis, including framework analysis with additional axial coding and member-checking of our findings, we determined the core reasons for WASH failure as perceived by participants.

Results Interviewees reported poor engagement and commitment of intended users, unrealistic and idealistic expectations held by funders and implementers, and a general lack of workforce and financial capacity as significant contributors to WASH failure. Our analysis shows that these issues stem from WASH programming being implemented as time and budget-constrained projects. This projectisation has led to reduced accountability of funders and implementers to intended users and a focus on measuring inputs and outputs rather than outcomes and impacts. It has also placed high expectations on intended users to sustain WASH services and behaviour change after projects officially end.

Conclusions Our findings imply that WASH programming needs to move away from projectisation towards long-term investments with associated accountability to local governments and longitudinal measurements of WASH access, as well as realistic considerations of the needs, abilities and priorities of intended users. Funders need to reconsider the status quo and how adjusting their systems could support sustainable WASH services.