The invention relates to a method for improving the separation of water in a tall oil preparation process which comprises: a neutralization step, in which a mixture of tall oil soap and water is neutralized with carbon dioxide; a water separation step, in which the aqeuous phase containing bicarbonate is separated from the tall oil soap; and a cooking step, in which the tall oil soap obtained from the previous step is cooked with sulfuric acid in order to form tall oil, the improvement comprising the fact that, after the neutralization with carbon dioxide but before the water separation step, the pH is adjusted with an acidically reacting substance, such as bisulfite. The invention also relates to a method for the preparation of tall oil, the method comprising the steps stated above.