The simplest route is to call the customer services number for your water supplier. Ask for the sodium level in the water supply and calcium carbonate hardness. (N.B. both sodium and calcium carbonate hardness must be expressed in mg/l. Divide the calcium carbonate hardness level by 2.175 and add the sodium in the water supply). This result should be no more than 200 mg/l of total sodium to comply with the Water Quality Regulations. As a “rule of thumb” if the calcium carbonate hardness level of the water supply is greater than 400 mg/l, there is a higher probability that the softened water will be close to or above the sodium limit in the Drinking Water Quality Regulations.
Or contact us for details of your nearest installer who can give you local advice.