Hello,

I finally decided to plumb in my lever machine (single copper boiler) and decided to try the BWT Bestmax Premium before I actually measured the water contents... Needless to say, things are not working out.

Water report from city:
KH = 16.2 dH
GH = 16.3 dH
calcium = 82.9 mg/l
magnezium = 21.9 mg/l
bicarbonates = 338.5 mg/l
chloride = 9.9 mg/l
pH = 7.5

pretty hard water. However, a new softening system was installed for the whole building about a year ago and my drop test kit shows GH = 9 dH and KH = 17 dH, pH = 7.

Now that is still pretty hard water with very high alkalinity. So I ran it trough the bestmax on bypass 1 and I get GH=4dH and KH=9dH with pH=6.5 which should result in about 55mg/l scale and with 6l per month consumption that would mean that 2g of scale will form in 6 months.

Is all the above correct? Or does the building softening system do something to the alkalinity so it doesn't create as much scale?
Should I be getting another filter to reduce the alkalinity first and then run trough the bestmax? Or should I get another BWT filter?

Appreciate any suggestions,
Thanks!

pinky-and-me wrote:[...] Is all the above correct?

Your scale rate calculation is probably conservative. If you calculate the calcium hardness of your tap water you get 11.6°dH, which is about 70% of the GH. So after the BWT filter your GH of 4°dH might have a calcium hardness of 3°dH or less, and if it's the Premium model, which exchanges some calcium with magnesium, the calcium hardness is likely even a bit lower. Watch for scale but very likely you won't see any buildup.

pinky-and-me wrote:Or does the building softening system do something to the alkalinity so it doesn't create as much scale?

Your numbers, where GH drops and KH stays the same, are consistent with a conventional softener that exchanges calcium and magnesium with sodium ions, leaving the bicarbonate the same. (Note - there are some systems, like template assisted crystalization (TAC) where the the GH and KH measures stay the same but scale formation is less likely. But I don't think you have that based on your numbers.)

pinky-and-me wrote:Should I be getting another filter to reduce the alkalinity first and then run trough the bestmax?

I think you may be OK with that BWT bestmax premium. Your high alkalinity helps alleviate the usual concern with WAC resins that acidify the water. The high remaining alkalinity (9°dH or 160 mg/L CaCO3 equivalent) after the filter is fine for machine health and probably will not detract from the taste of espresso (see Mixing three waters ) . It may produce a somewhat flat conventionally brewed coffee. If you wanted both low hardness and low alkalinity water in this case I think you'd want to go to reverse osmosis with a remineralizing cartridge.

So you only look at the calcium hardness? Doesn't magnesium produce scale as well? I've read the Insanely Long Water FAQ and that does factor in magnesium content into the hardness calculation.
I have ordered a calcium test kit so I will try to measure it after the fitter.

Another question: does the water temperature matter when I do the drop tests? Because I filled up a plastic water bottle last night (after washing it thoroughly with the same filtered water) and after about 24 hours the readings show GH=2dH and KH=7dH which is a 1 and 2 degrees drop from each type. The bottle was almost full with tight cap on so very little extra oxygen in there if that even matters. All the other measurements I've done are with very cold water.

I also tried a bestprotect cartridge and that dropped the GH to 0 but the KH was about 18 dH and pH was about 8.5. I don't suppose that would be better?

My first and biggest concern is scale because my machine doesn't have a flush valve and there is about 2 cm dead space on the bottom that I can't flush so descaling would be painful every time.

Thanks again for all the info and advice!

pinky-and-me wrote:So you only look at the calcium hardness? Doesn't magnesium produce scale as well? I've read the Insanely Long Water FAQ and that does factor in magnesium content into the hardness calculation.

The LSI estimate is based on calcium and limescale (CaCO3) deposition, so when doing that calculation you use calcium hardness if you have that. Magnesium carbonate is more soluble and scales differently. Most natural water has low magnesium relative to calcium so you can just calculate based on total hardness and figure that your scale deposition may be lower than your calculated estimate. If you are making water out of Epsom salts it can be a very significant difference. I'm not aware of any formulae for predicting scale from magnesium. Fans of magnesium-only Barista Hustle recipes have gone as hard as GH=100, KH=50 (mg/L CaCO3 equiv) and report seeing no scale.

The people selling BWT premium like to claim that magnesium enhances flavor and does not scale.

pinky-and-me wrote:I have ordered a calcium test kit so I will try to measure it after the fitter.

It might be interesting to see calcium before and after the BWT, but may be hard to pin down. Your numbers are pretty low compared to the drop test kits precision, and the effect from the BWT varies over the life of the filter. Let us know what you see.

pinky-and-me wrote:Another question: does the water temperature matter when I do the drop tests?

Hach are the undisputed leaders of drop titration kits, and their site says:

https://support.hach.com/app/answers/answer_view/a_id/1000227/loc/en_US#__highlight wrote:Samples below 21 °C should be titrated slowly near the endpoint because color development is slower. Samples previously boiled have their calcium bicarbonate hardness removed (precipitated), which lowers its Total Hardness as compared to a non-boiled sample. For Methods 8030 and 8374 best accuracy results require the sample temperature between 21-29 °C (70-84 °F).

homeburrero wrote: Hach are the undisputed leaders of drop titration kits, and their site says:

Aha, that explains why when I was testing I noticed that if I shook the tube more on the last drop the color kept changing. I will try the measurements again after warming the sample a bit with my hands.

Thanks!