The effects of continuous versus intermittent piped water supply

Piped water supply has often been referred to as a gold standard while evaluating access to water supply. For example, The Joint Monitoring Programme for Water Supply and Sanitation (JMP) rates piped water into the highest category while evaluating water access. The paper titled 'Upgrading a piped water supply from intermittent to continuous delivery and association with waterborne illness: A matched cohort study in urban India' published in the journal PLOS Medicine, argues that though widely considered the gold standard, the presence of a piped connection does not mean that it performs well in terms of quality, quantity, and frequency of water delivery. Piped water continues to be supplied intermittently in the vast majority of cities in low-income countries, with segments of the distribution network supplied with water on a rotating basis for a limited number of hours at a time.

Intermittent water provision through piped networks can increase the risk of waterborne diseases through contamination in non-pressurised pipes, recontamination during household storage due to use of unsafe alternative water sources, or limited water availability for hygiene. However, there are very few studies that have looked at the impact of intermittent delivery of piped water and the duration of intermittencies in water supply on the risk of illnesses among populations. This study in Hubli-Dharwad, Karnataka, India, compared outcomes of waterborne illnesses among children in areas with continuous versus intermittent water supply.

Findings of the study

• Tap water quality was significantly better under continuous supply, than under intermittent supply.
• Participants with continuous water supply also stored drinking water, and contamination during storage was common. However, the contamination of water samples was found to be more among households that had intermittent water supply as compared to those having continuous water supply.
• Municipal water consumption was higher under continuous water supply and met the recommendation of 50 liters per capita per day, while approximately half of the houses with intermittent supply fell short of this target.
• The study found that continuous supply was associated with lower prevalence of dysentery in children in low-income households as well as lower typhoid fever incidence, suggesting that intermittently operated piped water systems were a significant transmission mechanism for Salmonella typhi and dysentery-causing pathogens, despite centralised water treatment. Continuous supply was associated with reduced transmission, especially in the poorer higher risk segments of the population.
• Poorer households could experience larger health benefits from continous water supply as:
  
  • low income areas in Hubli-Dharwad had poorer sanitation infrastructure, which increased the risk of pathogen intrusion into pipelines when there was faecal contamination near waterlines. The protective impact of continuous pressure could be greater in low-income neighborhoods, where unsanitary conditions could lead to pathogen intrusion into pipes under intermittent pressure;
  • household water treatment was also more prevalent among higher-income groups. It was felt that improvements in municipal water quality would have a bigger health impact among low-income residents who consumed untreated water; and
  • higher-income households had access to high-capacity storage tanks, while lower-income households relied on small storage containers to secure water until the next round of the supply cycle. The lower income group thus experienced a bigger water strain during intermittencies and could benefit more from continuous supply.

Download a copy of the paper below.