Blue Tap



Blue Tap is a Cambridge-based social enterprise that aims to change the way the world consumes water. We use 3D printing to build a low-cost water purification technology for users in the developing world. We also design and sell bamboo and steel water bottles in the UK to raise awareness about water access issues across the globe and to fund our development projects.


With the Blue Tap chlorine injector, end-users can collect water through techniques such as rainwater harvesting, and then feel confident that the water they have collected is free of pathogens, and safe to drink. The use of the Blue Tap purifier can not only reduce the spread of waterborne disease but can also empower low-income populations to take control of their own drinking supply. We encourage families to have confidence to drink their tap water, reducing plastic waste and reducing the costs associated with continually boiling water.

Within the UK as part of our water awareness campaign, we sell the Blue Tap ‘Life Bottle’ range, a series of high-quality reusable bottles made from stainless steel and bamboo. The goal of the Life Bottle range is to generate our own revenue, raise awareness about the Blue Tap brand, and to encourage people in the developed world to consider how they consume water. Through the sales of our Life Bottles, we’ve helped people in the UK reduce their plastic footprint by cutting down their consumption of single-use bottled water. Since launching the range we’ve raised over £25,000 to fund our work in Uganda.

Technology & Innovation

Initially created for just $16, the Blue Tap Chlorine Injector (CI) aims to provide drinkable water to those who cannot trust the quality of their current water supply. Chlorine is widely acknowledged to be an effective water purification method, however, when used at a household level, there are often problems associated with dosing and mixing the chlorine correctly. When chlorine tablets or chlorine powder are used, they are frequently mixed incorrectly leading to over or under dosing. The result is water that either smells potently of chlorine and is therefore unpleasant to drink, or water that still contains dangerous pathogens.

The Blue Tap Chlorine Injector uses the venturi principle to inject chlorine into the water supply. This creates a low pressure (or ‘suction’) as the water passes through the vena contracta. This low pressure is used to drive the flow of aqueous chlorine from a reservoir into the water flowing through the venturi tube.

The beauty of the venturi design is that, as the water flows through it at a higher flow rate, the pressure in the vena contracta reduces (the ‘suction’ increases) and the chlorine flow rate increases. In theory, this maintains a constant ratio between the chlorine flow rate and the water flow rate and therefore ensures a constant chlorine dosage. This removes human error from the dosing process and adds the correct chlorine concentration to the water supply.

The team

Francesca O’Hanlon: Francesca has spent nearly five years working as a water and sanitation engineer in El Salvador, Mexico, India, and most recently with Medecins Sans Frontiers in two of the poorest countries in the world: South Sudan, and Central Africa Republic. Francesca built the idea for Blue Tap after working with plumbers all over the world and repeatedly hearing that we need a better way to reliable chlorinate water. She is in the second year of my PhD in Engineering at Cambridge.

Tom Stakes: Tom has just graduated from his 4th year in engineering at Cambridge with a first class degree. He focused on fluid dynamics and has recently completed a 3-month internship with the World Health Organisation. He has taken the chlorine injector from the very first prototype to the impressive design you can see on our website today.

Becky Donaldson: Becky is a third-year engineering student who has spent 2 months volunteering with the Cambridge Development Initiative in Tanzania. She oversaw local entrepreneurship projects there and is in charge of operations for Blue Tap.

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