The invention relates to a method for manufacturing a liquid acid concentrate for hemodialysis machines, with the following steps. In a preliminary step a water source (120), an acid source (130), an electrolyte tank (140) containing a mixture of electrolytes in exactly the quantity needed for the manufacture of the liquid acid concentrate, and a sodium chloride source (150) are connected to a mixing tank (110). During Step a), the quantity of water needed for the manufacture of the batch of liquid acid concentrate is introduced into the mixing tank (110). At Step b), the quantity of acid needed for manufacture the liquid acid concentrate is introduced into the mixing tank (110), the solution is stirred until a homogeneous solution is obtained. Step c) is to repeat Sub-steps c1) and c2) until the electrolyte mixture contained in the electrolyte tank is completely dissolved. At Sub-step c1) part of the solution contained in the mixing tank (110) is transferred into the electrolyte tank (140) containing the electrolyte mixture, then at Sub-step c2) the solution contained in the electrolyte tank (140) is transferred into the mixing tank, leaving the still solid constituents in the electrolyte tank. At Step d) the quantity of sodium chloride needed to manufacture the liquid acid concentrate is introduced into the mixing tank (110). Finally, at Step e), the solution is stirred and recirculated by taking it from the bottom the mixing tank (110) and reintroducing it at the top of the mixing tank until a homogeneous liquid acid concentrate is obtained. Steps a) to d) can be performed in any order, Step a) preceding always Step c).