Coffee Calculators

Water chemistry

Descaling Frequency Calculator

Scale is GH minerals left behind as water boils. Harder water and more shots fill a small boiler faster. This is a crude capacity model so you descale before the PID lies and the group cools. Soft barista water stretches the interval; 180 ppm tap water does not.

Inputs

Units
ppm

GH as ppm CaCO₃ of the water that actually enters the boiler.

Including wasted dial-in. Steam-only days still count if you heat the boiler.

ml

Brew boiler if you have two. A 2 L HX is not a 300 ml single boiler.

Results

Days until descale
30days
Shots until descale
240

Recommended gear

Calculation method

A reference machine at 180 ppm, 8 shots/day and 300 ml is treated as a 30-day descale. Your days scale inversely with hardness and shots, and stretch with a larger boiler (more water mass before the same scale fraction). Shots until descale is days times shots per day. Soft 80 ppm water at the same habit lasts longer; twice the shots cuts the calendar in half.

Exact formula

scaleIndex = hardnessPpm × shotsPerDay × (boilerVolumeMl / 300). daysUntilDescale = clamp(7, 365, 43200 / scaleIndex). Reference: 180 ppm, 8 shots, 300 ml → 30 days. Limits: Steam vs brew boiler, temperature, and ‘descale’ vs ion-exchange omitted; empty the machine’s manual over this guess.

Warranty water

Many prosumer manuals cap hardness. If you are outside it, the frequency number is how often you pay for that choice.

Frequently asked questions

I use recipe water at 80 ppm. Still descale?

Yes, less often. Soft water still leaves some scale and coffee oils. Stretch the interval; do not delete the task.

Dual boiler?

Enter the boiler you care about, or run twice. Steam boilers often see more concentration from makeup water.

Backflushing vs descaling?

Backflush detergent is oils and the group. Descale is minerals in the boiler. They are not substitutes.

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