Hi friends, I just got the API kit to test my brita-filtered water hardness for my new La Marzocco Linea Micra. I ran both KH and GH on unfiltered tap water and the water filtered through my brita.

Unfiltered Tap: KH 1(17.8 ppm) and GH 3 (53.4 ppm)
Filtered Brita: KH 1 (17.8 ppm) and GH 1 (17.8 ppm)

My naive understanding is that this is acceptable water hardness for the machine. I ask because I ran the same water in my previous Rocket Apartamento and had the hot water tap clog up with scale a couple of times, despite proper backflushing, etc.

coffeenewb56 wrote:Unfiltered Tap: KH 1(17.8 ppm) and GH 3 (53.4 ppm)
Filtered Brita: KH 1 (17.8 ppm) and GH 1 (17.8 ppm)
My nieve understanding is that this is acceptable water hardness for the machine.

If those are accurate measures I'd say that's on the soft side of acceptable. Might be worth retesting with a stretched sample**. If you're on NYC water, you expect the water to be fairly soft, but having 53 ppm hardness with only 18 ppm alkalinity seems pretty odd.


There are different Brita filters out there. Most of them contain a decarbonizing resin that tends to reduce hardness and alkalinity by an equal amount, but can't be relied on to do that predictably over the life of the filter. If you're using a North American Brita pitcher filter, then you can use the newer Longlast/Elite filter, which has activated charcoal filtration but with no ion exchange resin at all. It should leave both your hardness and your alkalinity at the same levels as your tap water, which is probably a good idea in this case.

coffeenewb56 wrote:I ran the same water in my previous Rocket Apartamento and had the hot water tap clog up with scale a couple of times, despite proper backflushing, etc.

If you use the steam wand a lot, your water in the steam boiler can get very concentrated and become scale prone. You can address this by routinely draining or flushing the steam boiler. If the water is as soft as yours appears to be, you can use this approach: Using hot water tap to manage steam boiler water concentration


** When your readings come out at less than a few drops you can get better precision by using a stretched sample. For the API kits, which normally use a 5 ml sample, you can instead use a 10 ml sample, and then every drop of titrant corresponds to 8.9 ppm CaCO3 equivalent rather than 17.8 ppm.