Note: This page summarizes the rationale behind a GiveWell grant to Mangrove Water. Mangrove Water staff reviewed this page prior to publication.
Summary
In January 2025, GiveWell recommended a $236,958 grant to Mangrove Water for the first phase of the development of an attachment for its in-line chlorination device, the TuriTap, that would allow the device to work on handpump water points. If this development is successful, and Mangrove Water receives subsequent funding to bring the product to mass manufacturing, this could allow for the consistent in-line chlorination of handpumps at scale for the first time.
We’re recommending this grant because:
- If this product development is successful, it could allow us to make grants that are more cost-effective than we would otherwise be able to make. This is because we associate in-line chlorination with higher chlorination rates than the forms of chlorination that are currently suitable for the treatment of handpump-provided water.
- In-line chlorination might be more straightforward to implement on handpumps than those other forms of chlorination, so it might also increase the number of implementers of chlorination programs — which could increase GiveWell’s cost-effective funding opportunities in the water quality space.
- We think other funders and organizations might be interested in in-line chlorination for handpumps if an effective handpump chlorinator were commercially available.
- We think Mangrove Water is the right organization to work on this product development.
Our main reservations are:
- It’s possible that this product development will be unsuccessful, in which case we wouldn’t expect any benefits from this work.
- Even if the product development is successful, in-line chlorination for handpumps might not be a viable or cost-effective use of funding for other reasons, such as unforeseen implementation challenges, unreliable liquid chlorine supply chains, or high costs.
- We don’t know of specific organizations who are ready to adopt this device.
- This product development might have limited generalizability, in that it would only allow for the adaptation of one specific liquid-dosing in-line chlorinator, the TuriTap, and it could turn out that another device is better or more appropriate in some contexts.
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 (more).
The intervention
In-line chlorination (ILC) is one of the two chlorination interventions to which GiveWell has directed significant funding to date, alongside chlorine dispensers.3 In-line chlorinators are typically installed on a pipe feeding a water storage tank. As water flows past the chlorinator, it disinfects the water.4
Our understanding is that there are no in-line chlorination devices that work reliably on handpumps,5 which are a common source of water in rural and peri-urban parts of sub-Saharan Africa.6 Mangrove Water attributes this to the fact that conventional tablet erosion chlorination devices require consistent water pressure to achieve accurate, consistent dosing, whereas handpumps generate low and highly variable flow rates.7 The lack of an effective handpump chlorinator means that GiveWell is limited to funding active chlorination methods for handpump-sourced water (i.e., methods that are dependent on conscious user behavior, such as chlorine dispensers or vouchers), which we associate with generally lower chlorination rates than ILC.8
Mangrove Water has developed its own in-line chlorination device, the TuriTap, which uses liquid chlorine, rather than solid chlorine tablets. It believes that, with an additional attachment, the TuriTap could achieve consistent chlorine dosing on handpumps too, potentially allowing for the application of in-line chlorination on these handpumps at scale for the first time.9
The grant
This grant will fund Mangrove Water to begin developing the attachment that would allow its proprietary in-line chlorination device, the TuriTap, to attach to handpumps.10 With this grant funding, and if the initial development is successful, Mangrove Water expects it will get as far as field testing a proof-of-concept prototype device in Kenya, but it will require additional funding to bring the device to at-scale manufacturing.11
This initial period of development will take 18 months. This breaks down as follows:12
- Prototyping and testing – 4 months
- Proof-of-concept prototype refinement – 6 months
- Field pilot in Kenya (including preparations) – 8 months
The case for the grant
We are recommending this grant because:
- If this product development is successful, it could allow us to make grants that are more cost-effective than we would otherwise be able to make. If Mangrove Water is successful in developing the attachment, and if it turns out to be appropriate for implementation at scale, we would consider recommending grants for in-line chlorination on handpumps in the future. We think it’s plausible that such grants would be more cost-effective than the grants we could currently recommend for the chlorination of handpump-provided water, as we are currently limited to manual chlorination methods, like dispensers or chlorine vouchers, which we associate with lower chlorination rates than in-line chlorination.13 We think this is particularly promising because our general impression is handpumps tend to be most common in rural and peri-urban areas, which we broadly associate with where we’ll find the most cost-effective room for more funding for chlorination. Intuitively, therefore, a handpump in-line chlorinator could amplify the cost-effectiveness of our funding in some of the areas we would be most interested in making grants.
- If the development of the adapter proves to be successful, it could unlock additional, cost-effective funding opportunities for GiveWell. Our impression, based on talking to several prospective grantees, is that many smaller or less-experienced organizations may find dispenser programs too onerous to implement.14 In practice, this limits our additional grantmaking for chlorination, even in otherwise highly cost-effective locations, because it prevents us from recommending grants for the chlorination of handpump-provided water in areas where these smaller organizations might otherwise be the most appropriate grantee. Therefore, if the TuriTap adaptation is successful, and if handpump chlorination using this new device is not more complex to implement than other forms of in-line chlorination, significant new grantmaking opportunities could be opened up in the future by such easier-to-implement chlorination opportunities for handpump infrastructure.
- We think the option of funding in-line chlorination for handpumps could be of interest to the broader water sector. We think it is plausible that if a handpump chlorinator were commercially available, other organizations working in the water sector might choose to purchase and install them of their own volition (and/or other funders might provide funding for them to do so). Our understanding is that at least two other organizations have worked on developing a scalable handpump chlorinator in the past, which we take as an indication that there is demand for this device beyond GiveWell.15 If Mangrove Water succeeds in bringing the TuriTap attachment to mass manufacturing, it would plan to offer it for sale, which we think means it is plausible that other organizations could purchase it without our direct involvement or encouragement.16
- We think that Mangrove Water is the right organization for this grant. 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.17 In addition, Mangrove has already done some lab testing of the device, which it says showed encouraging results.18
Risks and reservations
Our main reservations about this grant are:
- It’s possible that the product development fails. For example, Mangrove Water may not be able to develop a functional prototype, or the subsequent mass manufacturing of the device could prove to be significantly more difficult than we expect. If this happens, none of the benefits outlined above would materialize. Of these risks, our impression is that the former is the most significant, since Mangrove Water expects to have brought the underlying TuriTap device to market later in 2025, and will therefore have some experience with scaling up device manufacturing from the prototype stage.
- Even if the TuriTap can be manufactured cheaply and at scale, in-line chlorination for handpumps might not be viable (or cost-effective) for other reasons. For example, potential issues may include:
- Implementation: In general, on-the-ground implementation issues seem relatively more likely for a new handpump in-line chlorination program relative to a dispensers program, since chlorine dispensers have been implemented and refined over time. As one example, we have heard anecdotally that in-line chlorination devices can be prone to theft or vandalism if they are not installed high above ground. Therefore, it seems possible to us that vandalism could be an issue, particularly if chlorine taste acceptability is low.19 In turn, low chlorine acceptability might make it more difficult for organizations who are less used to sensitization work to expand into handpump chlorination, which could reduce the extent of the possible new grantmaking opportunities discussed above.
- Cost-effectiveness: An at-scale handpump in-line chlorination program may not be as cost-effective as a dispensers program, even if product development is successful. While we would expect such devices to deliver higher chlorination rates than dispensers, it’s possible this benefit could be offset by other factors, such as higher costs on a per-person-reached basis. Our rough understanding is that in-line chlorination generally looks cost-effective when its costs are amortized over a large number of users, but handpumps may serve many fewer people than other systems that use in-line chlorination, such as piped systems and gravity-fed tanks. At this stage, however, this reservation is entirely speculative.
- Supply chains: We do not know how easy it will be to source good-quality liquid chlorine, which the TuriTap requires. Our impression is that chlorine supply chains are generally unreliable and highly variable across geographies, and it’s possible sourcing liquid chlorine is more (or less) difficult than we’ve experienced so far with chlorine tablets. This could potentially make liquid dosing in-line chlorination devices unfeasible at scale; again, this reservation is entirely speculative at this stage.
- We don’t know of specific organizations who are ready to adopt this device. The case for the grant relies on our assumption that organizations would be interested in using the device if it was available and if GiveWell provided funding for it. While we feel confident in this assumption, we haven’t yet run it past specific organizations, so it’s possible that we are wrong.
- This work might have limited generalizability. Mangrove Water’s adapter will only be compatible with the TuriTap, although Mangrove says it is open to exploring modifications that could make it compatible with other liquid dosers in the future.20 We don’t know the liquid doser landscape well (so it’s possible this is a non-issue, and that the TuriTap is simply better than the alternatives), but this means the value of this research might be limited if it turns out that other devices are better-suited to handpump chlorination.
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 product’s development through our existing lines of communication. We do not expect to renew this grant in the future.
Our process
- GiveWell recommended this grant via our policy for small discretionary grantmaking. As a discretionary grant, this funding opportunity did not receive the same in-depth review as larger grants we recommend. Instead, we more minimally evaluated the case for the grant along with any potential risks or downsides.
- We have been in regular contact with Mangrove Water for some time, and we met Megan Lindmark in-person at the World Water Week conference in August 2024.
- We asked Mangrove Water to submit a proposal for this device, and we received the proposal for this grant in December 2024.
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 the organization’s Contact page. For their previous work related to in-line chlorination, see especially Pickering et al. 2019 and Lindmark et al. 2022, as well as Pickering et al. 2021, which describes the Venturi (liquid) chlorinator that Mangrove Water plans to make commercially available as the “TuriTap”.
- 3
For more on GiveWell’s approach to chlorination to date, see our blog post on GiveWell’s water research strategy.
- 4
See this section of a previous GiveWell grant page for an in-line chlorination program in Malawi, which compares ILC to Evidence Action’s “Dispensers for Safe Water”, for more details. Note that this description is of a tablet erosion chlorinator, the only type of in-line chlorinator GiveWell has funded at scale to date. It’s possible that injection chlorinators work in a somewhat different way.
- 5
This is based on several conversations we had with water quality experts in 2024.
- 6
One estimate suggests handpumps serve 184 million people across sub-Saharan Africa (Rural Water Supply Network, “Handpump Standardisation in Sub-Saharan Africa”, p. 2).
- 7
Mangrove Water’s proposal (see “Aim 2: Adapt the TuriTap to chlorinate water at manual handpumps”) for this grant asserts: “Manual handpumps often generate low, variable flow rates which pulse with each stroke of the handle. Variable flow rates can inhibit the dosing control of other in-line chlorinators which require consistent flow rates through a bypass line to control dosing” (p. 2).
- 8
As a rough benchmark, at the time we made our 2022 grants to Evidence Action for dispensers and for in-line chlorination, we expected chlorination rates to be 45%–60% for dispensers (varying by location) and 68% for in-line chlorination.
- 9
The TuriTap is a non-electrified in-line chlorination device that uses liquid chlorine, rather than chlorine tablets (which Evidence Action’s in-line chlorination devices use). Tablet devices require consistent flow in order to achieve accurate and consistent dosing; similarly, as sold, the TuriTap will require “consistent flow rates between 5 to 60 liters per minute”. However, Mangrove’s proposal for this grant claims that “the fluid dynamics principle (the Venturi effect) used by the TuriTap to dose chlorine [will] be able to effectively chlorinate intermittent flows through the device” if the device is modified for this purpose.
- 10
- The TuriTap is a new device; Mangrove has just begun to manufacture at scale (Amy Pickering, email to GiveWell, January 11, 2025 (unpublished)).
- Mangrove says it expects this “to be an attachment (adaptor) to the standard TuriTap design”, rather than a modified TuriTap design. For more context: “We have already invested in manufacturing tooling for the standard TuriTap design which works well for piped water supply delivered at taps. Ideally, this adaptable attachment would allow for a TuriTap to be installed at a wide range of existing handpumps. Depending on our prototyping and lab testing, it could make sense to design a model of the TuriTap for handpumps only but this would require more expensive tooling and require a longer timeline.” Amy Pickering, email to GiveWell, January 11, 2025 (unpublished).
- More information about common types of handpumps and their infrastructure is available in this Rural Water Supply Network field note.
- 11
- Mangrove believes this pilot will be “very generalizable”, as “most existing community handpumps are based on the two open source models you mentioned: India Mark II/III and Afridev. There is a great resource online from the Rural Water Supply Network that discusses the history of these models and their widespread use, linked here. More importantly, the flow conditions across many of these handpumps are similar, where they provide pulses of water/low flow with each stroke of the hand pump handle. We intend to use these two hand pumps models as design constraints so the attachment is as adaptable as possible to the most common hand pumps”. Amy Pickering, email to GiveWell, January 11, 2025 (unpublished).
- Mangrove describes its proposed field test in Kenya as follows: “We expect to install 2 prototypes at community water points in Kenya with an implementing partner who will monitor their performance over time. With our guidance, the implementing partner will identify community handpump water points, obtain permission for installation, install the TuriTap prototypes, service them (i.e. refills), and obtain user feedback through short surveys. We will monitor their performance over a 3-month period and survey between 10-30 people on their experience with the prototype and perceptions of chlorinated water. We expect 3 months to provide enough time to learn of any failure points, monitor performance over time, and obtain feedback from users.” Mangrove Water, “Concept Note: Advancing the field of in-line chlorination through technology and resource development”, December 2024, p. 2.
- Mangrove says it is interested in continuing product development if this first stage is successful: “It is our goal to continue the pursuit of development and manufacturing beyond this initial prototyping and pilot phase. Like we mentioned above, we think this prototyping phase will lead to a production validation prototype, and if it performs well in the field, then Mangrove would be interested in creating a mass manufacturable version (drawing on our experience manufacturing the TuriTap). The handpump-adapted TuriTap would then be an additional technology available in Mangrove Water’s suite of technologies for sale.” Amy Pickering, email to GiveWell, January 11, 2025 (unpublished).
- Mangrove expects that creating a mass-manufacturable design and toolings would cost around a further $210k (so a $400-450k budget all in). On the process required after this grant to get to mass manufacturing, Mangrove wrote: “The cost of designing and producing the tooling to manufacture the envisioned attachment at scale would depend on the design, size, material, and number of pieces required to build it. The objective of this initial grant is completion of a production validation prototype (~75% of the way to manufacturing). If all goes well in this prototype development and piloting, for the next revision would require time of a mechanical design engineer to create a manufacturable design and part drawings for the attachment which can be used to build tooling and start mass production. It is difficult to provide an accurate estimate until we have a working prototype, but we estimate personnel time to be approximately $150k, and the manufacturing tooling assets and supplies to be approximately $60k.” Amy Pickering, email to GiveWell, January 11, 2025 (unpublished).
- 12
Mangrove Water, “Concept Note: Advancing the field of in-line chlorination through technology and resource development”, December 2024, p. 3.
- 13
As a rough benchmark, at the time we made our 2022 grants to Evidence Action for dispensers and for in-line chlorination, we expected chlorination rates to be 45%–60% for dispensers (varying by location) and 68% for in-line chlorination.
- 14
This is based on specific concerns we’ve heard from organizations about the difficulty of implementing a dispensers program relative to in-line chlorination.
- 15
For one example, see Aquaya, “Willingness-to-pay for the ‘NuPump’ Inline Handpump Chlorinator.” The other example we are aware of is confidential.
- 16
“The handpump-adapted TuriTap would then be an additional technology available in Mangrove Water’s suite of technologies for sale. We see considerable potential and benefit for bringing this adaptation to market given the global population of handpump users and organizations that service handpumps.” Amy Pickering, email to GiveWell, January 11, 2025 (unpublished).
- 17
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. Megan Lindmark has extensive on-the-ground implementation experience with Cova.
- 18
“They think this is promising. They’ve done lab testing which looks promising, but not enough to feel confident.” GiveWell, conversation with Mangrove Water, December 5, 2024 (unpublished).
- 19
For more on issues with chlorine acceptability in program contexts, see this section of our review of chlorine vouchers as an intervention.
- 20
“At this time we would like to only commit to an adapter compatible with the TuriTap. However, we could do some testing and explore what modifications would be possible to make it compatible with other selected dosers.” Amy Pickering, email to GiveWell, January 15, 2024 (unpublished).