I just bought a miele 4840. I use persil and want to know does anyone add baking soda and how much to soften hard water. I am also trying to keep the hard water from ruining my machine.
I have very hard water too, but never heard of using baking soda. I use 20 Mule Team Borax, a scant tablespoon along with Biokleen laundry powder. My machine is small -- an Asko European-sized -- and I do small loads, so a tblsp. of each is all I need. The Asko manual suggests adding 1 oz of citric acid into the wash drum and running a 205 degree program to remove deposits that may form on the wash drum. I've never had to do this.
Baking soda can make hard water "harder". Depending on where you are in the country you may already have a high level of bicarbs in your water. Borax would be a better choice.
Forgot to add that Persil alone will likely be adequate for hard water. It is formulated for hard water and to eliminate build up.