Peatlands are globally‐important terrestrial carbon stores as well as regional sources of potablewater supply. Water draining from peatlands is rich in dissolved organic carbon (DOC), which can beproblematic for water treatment. However, it is unclear how future climate and sulfate deposition changesmay impact DOC in peatland‐derived potable water. The United Kingdom (UK) is a global hotspot thatconsumes 79% of all potable water derived directly from peatlands. Here, a physically‐based hydrologicalmodel and a biogeochemical organic carbon model were used to predict discharge and DOC concentrationin nine hotspots of peatland‐derived potable water use in the UK under a range of 21st century climateand sulfate deposition scenarios. These nine catchments supply 72% of all peatland‐derived water consumedin the UK and 57% of the global total, equivalent to the total domestic consumption of over 14 millionpeople. Our simulations indicate that annual discharges will decrease and that mean annual DOCconcentrations will increase under all future scenarios (by as much as 53.4% annually for the highestemissions scenario) in all catchments. Large increases (by as much as a factor of 1.6) in DOC concentrationin the 2090s over the baseline period are projected for autumn and winter, seasons when DOCconcentrations are already high in the baseline datasets such that water treatment works often reach theircapacity to cope. The total DOCflux is largely insensitive to future climate change because the projectedincrease in DOC concentration is mostly counterbalanced by the projected decrease in discharge.