Thinking about plumbing in my new machine, the city claims our water is moderately soft (40-60 mg/L CaCO3 or 2.3-3.5 grains /gallon).

1) Should I use some sort of water treatment? or just descale every 3-6 months? 6-9months? 9-12months?
2) Is this enough info to judge whether or not to treat my water?
3) My machine has a dedicated boiler for brewing and thermoblock for steam (not sure if that makes a difference)
4) I generally pull between 2-3 doubles in a day, maybe one milk drink (more if company come over)

The advice of the resident water experts is greatly appreciated.

Just found that alkalinity is 27mg/L if that helps.

Using your highest reading of 3.5 grains you have soft water (17.1 x grains = PPM) which means you are at about 60 PPM. You may need to descale once every few years but you certainly dont need any water treatment. If anything, you need harder water.

You may want to read over these links

Jims insainly long water FAQ

And the SCAA's official water document.

http://www.scaa.org/PDF/ST%20-%20WATER% ... V2009A.pdf