BWT tablet salt is essential for use with all BTW water softeners and is available in 10kg bags.When you purchase your water softener, we recommend you add the high quality tablet salt to the correct level set out in the installation instructions, so your appliance is ready to go.From time to time depending on the amount of water usage in your house, you will need to top up the unit with more salt. An audible alarm sounds and the unit displays the word SALT letting you know when. We recommend you purchase the required number of bags of salt for your first month at the time when you purchase the softener.We do not recommend the use of any other type of salt with the BWT Luxury Water softener. For a 4 person household, each using 120 Litres per day, c. 4 x 10kg bags would be required per month. For a single person household using 120 litres per day, c. 1 x 10kg bag would be required per month.