The invention relates to a water treatment system (1) for dialysis treatments, wherein the water treatment system (1) comprises a permeate circuit with a reverse osmosis system (RO) and at least one tap (ES1, 2 . . . N) for permeate, whereby the reverse osmosis system (RO) is fed by the reflux of the at least one tap (ES1, 2 . . . N) for dialysis treatments and/or a raw water inflow (RZ), whereby the water treatment system further comprises a heat exchanger (WT), whereby a primary circuit (PK) of the heat exchanger (WT) is connected with a buffer tank (PT) for storing thermal energy, whereby a second circuit (SK) of the heat exchanger (WT) is integrated into the permeate circuit, whereby heat is transferred in a controlled manner from the buffer tank (PT) via the heat exchanger (WT) to permeate in the permeate circuit.
