Note: This page summarizes the rationale behind a GiveWell grant to Mangrove Water. Mangrove Water staff reviewed this page prior to publication.
Summary
In December 2024, GiveWell recommended an $88,550 grant to Mangrove Water for the creation of an implementation guide for organizations considering implementing in-line chlorination programs.
We’re recommending this grant primarily because our impression is that a lack of technical information about in-line chlorination acts as a barrier to entry for potential new implementers. We think this guide will help organizations understand what in-line chlorination requires, and will increase the probability that organizations that choose to implement in-line chlorination do so effectively. This feeds into one of the core goals of our water grantmaking portfolio – expanding the number of organizations that GiveWell funds to implement chlorination programs at scale.
We do not have significant reservations about this grant, though we expect the guide may become less useful over time as implementation practices improve.
Published: April 2025
The organization
Mangrove Water is a new organization that provides advice and support for the implementation of in-line chlorination programs.1 It was established by Amy Pickering, Megan Lindmark, and Jeremy Lowe, three in-line chlorination experts.2 GiveWell recently provided Mangrove Water with funding to provide remote technical assistance to Uduma for its pilot of in-line chlorination on its water systems in Mali, for which we recommended funding in November 2024.
The grant
This grant will fund Mangrove Water to develop a comprehensive guide to the implementation of in-line chlorination. The guide will include information on the selection and installation of suitable infrastructure, on operation and maintenance, and on best practices for monitoring and evaluation.3 Mangrove Water intends to publish the guide on its website and disseminate it among relevant water sector convening organizations.4 GiveWell will also share the guide with organizations that advance through the process of our public request for information for chlorination programs.
We expect that parts of the guide will be ready by May 2025. Two sections – updated designs and building instructions for open-source tablet dosers, and in-line chlorination case studies – will be ready later, by January 2026.5
The case for the grant
We are recommending this grant because:
- An implementation guide could increase the likelihood of new organizations operating an effective in-line chlorination program. One of the core goals of GiveWell’s water grantmaking team is to expand the number of implementers of chlorination programs. Our current grantmaking relies heavily on Evidence Action, which does not operate in some of the places where we think chlorination could be most cost-effective, such as parts of Francophone Africa.6 We think that having a guide for the implementation of in-line chlorination (one which covers where and how the intervention can be operated), will materially reduce the barriers to entry for new organizations, thereby helping us to fulfil this goal. We think this because we see in-line chlorination as a less ‘manualized’ program than chlorine dispensers, the other main chlorination intervention we have funded to date.7 In other words, our view is that implementing in-line chlorination requires significant in-house technical capacity and expertise, as there are currently no detailed reference points that organizations can draw from. This guide should help to address this, for instance by helping organizations to understand which types of existing water infrastructure are compatible with which in-line chlorination devices.
- We think that Mangrove Water is the right organization to produce this guide. We have a strong qualitative impression of Mangrove Water, primarily based on their research track record, as well as extensive experience of on-the-ground implementation.8 We are confident that Mangrove Water has the technical expertise to produce a high-quality guide that is responsive to organizations’ needs.
- We expect we’ll get some signal on whether or not this guide has the effect we hope for. Although we won’t learn what would have happened had we not recommended this grant, we do expect to receive qualitative feedback that should tell us whether or not this grant was successful. For example, we will find out whether or not organizations that we know of (or which we learn about through our public request for information) find the guide useful or relevant. If they do find it useful, we also expect to receive qualitative feedback on whether it made them more likely to implement in-line chlorination, and made implementation materially more straightforward or effective than they think it otherwise would have been.
Risks and reservations
Given the small size of this grant, we do not have significant reservations. However, we think there are two factors that may limit the impact of the guide over time:
- The manual may fall out of date. In-line chlorination is still a maturing intervention. As implementation techniques and best practices improve, some of Mangrove Water’s guidance may become less relevant over time. However, if this guide is successful in encouraging implementers to adopt in-line chlorination, they may develop their own internal processes, which would mitigate this concern.
- We don’t know how many organizations will read the guide and change their plans as a result. Although we feel confident that there is a sufficient audience for an in-line chlorination implementation guide (based on our request for information for chlorination programs, and feedback from experts who we have consulted over the past year), we don’t know far this guide will travel beyond our immediate network, and whether it will be enough by itself to lead new organizations to implement in-line chlorination. This means we’re uncertain about the size of the upside potential of the grant.
Plans for follow up
We are in regular contact with Mangrove Water as a result of other projects (like the technical assistance Mangrove Water is providing for Uduma’s in-line chlorination pilot in Mali), so we expect to hear about the progress of the guide through our existing lines of communication. We do not expect to renew this grant in the future.
Our process
- In 2024, GiveWell’s water grantmaking team sought to identify opportunities to further the ‘manualization’ of both chlorine dispensers and in-line chlorination.
- Mangrove Water suggested creating the implementation guide. We have been in regular contact with Mangrove Water for some time, and met Megan Lindmark in-person at the World Water Week conference in August 2024.
- Since this is a small grant that we feel particularly confident in, we conducted only a brief grant investigation, based on our familiarity with Mangrove Water and the proposal we received.
Sources
- 1
“Mangrove Water provides advice and resources to support implementation of inline chlorination globally.” Mangrove Water, ‘Home’.
- 2
The co-founders of Mangrove Water are listed on their Contact page. For previous work related to in-line chlorination, see especially Pickering et al. 2019, Lindmark et al. 2022, and Pickering et al. 2021, which describes the Venturi (liquid) chlorinator that Mangrove Water plans to make commercially available as the TuriTap.
- 3
“We aim to create an implementation guide including the following components:
- Infrastructure assessment guidance for implementers to determine if in-line chlorination is a good fit for their existing infrastructure
- List of available in-line chlorination technologies and how to procure them
- Recommended infrastructure and technology pairings under given constraints (i.e. flow rates, existing supply chain, operational needs, etc.)
- Updated designs and building instructions for open-source chlorine tablet erosion dosers
- Operation and maintenance guidance
- Best practices for monitoring in-line chlorine doser performance (chlorine residual testing) and microbial water quality
- Selected in-line chlorination case studies.”
Mangrove Water, Concept Note: Advancing the field of in-line chlorination through technology and resource development, 2024 (unpublished).
- 4
"We will publish this guide to our knowledge sharing platform to be hosted on the Mangrove Water website. We will also support dissemination of this guide to convening organizations in the global WASH field such as the USAID, the World Bank, Rural Water Supply Network, Global Water Center, and more." Mangrove Water, Concept Note: Advancing the field of in-line chlorination through technology and resource development, 2024 (unpublished).
- 5
"Timeline:
- Tasks 1,2,3,5, and 6 will be completed within 5 months (May 2025 if contract signed Jan 2025)
- Tasks 4 and 7 will be completed within 12 months."
Mangrove Water, Concept Note: Advancing the field of in-line chlorination through technology and resource development, 2024 (unpublished).
- 6
- 7
This view is based on our conversations with a number of water experts over the past year.
- 8
As above, see especially Pickering et al. 2019, Lindmark et al. 2022, and Pickering et al. 2021, which describes the Venturi (liquid) chlorinator that Mangrove Water plans to make commercially available as the TuriTap.