Every litre sold through Nisa outlets raises 3p for The One Foundation, a global initiative that supports clean water, sanitation and hygiene.
Some £100,000 has been raised in just four months for the charity and, since Nisa became part of the Co-op group in 2018, its retailers have raised almost £627,000 to support its work.
The latest landmark comes just months after Nisa retailers reached £500,000 in donations to the water charity.
Danielle Slyvester, wholesale category controller at Nisa, said: “It is wonderful that by doing something as simple as stocking Co-op water in their stores, our partners can make such a valuable contribution to a brilliant charity.
“To reach another milestone donation total within months of hitting the half a million mark is just fantastic.”
Working in partnership with The One Foundation, the Co-op has spent the last 12 years investing in clean water, sanitation and hygiene projects around the world.
To date, Co-op sales have raised more than £10m for clean water projects to support many global projects undertaken by the charity.