Three machines, three different enemies
A commercial kitchen's water problems concentrate in three places: the espresso machine (scale and taste), the combi oven (scale and chloride corrosion), and the ice machine (taste, odour and sediment). Treat them as one problem and you will solve none of them well — the coffee machine wants some mineral content, the combi oven may need it removed, and the ice machine mostly needs chlorine and particles gone.
Coffee: the SCA water targets
The Specialty Coffee Association publishes actual numbers for brewing water, and they are not "as pure as possible". The published targets: total hardness around 68 mg/L as CaCO3 (acceptable roughly 50 to 175), alkalinity around 40 mg/L as CaCO3, pH near 7, TDS around 150 mg/L, and chlorine fully removed. That is the association's water standard as commonly quoted; it has been revised, so work from the current published version and from the machine maker's own requirement where the two differ. Espresso extraction is chemistry — calcium carries flavour extraction and alkalinity buffers acidity — so water that is too soft makes flat, sour coffee while hard water scales the boiler and group head.
The practical treatment for most South African municipal supplies is a scale-control cartridge (ion-exchange or polyphosphate types sized for the machine) plus carbon for chlorine. Full RO under the counter is only the right answer on genuinely bad water, and then it needs blending or remineralisation back toward the SCA window — straight RO permeate is outside it.
Combi ovens: read the manual, then test for chloride
Combi steamers are the most specification-driven water users in the kitchen, and the numbers come from the manufacturers themselves. Convotherm's installation requirements for its C4 range: hardness between roughly 70 and 360 mg/L as CaCO3, chloride at or below 60 mg/L, free chlorine at or below 0.2 mg/L, pH 6.5 to 8.5, and conductivity of at least 20 µS/cm. Rational's documentation runs on the same logic — carbon filtration above 0.2 mg/L chlorine, and reverse osmosis required once chloride climbs (their published threshold is 80 mg/L), because chloride attacks stainless steam generators in ways hardness never will.
Two traps are worth naming. First, chloride, not hardness, writes off combi ovens — and softeners do not remove chloride, so a softened supply can still be corroding the steam generator. Second, fully demineralised water is also out of spec: the manufacturers set minimum conductivity because ultra-pure water is aggressive to the machine and useless to the level probes. The right train depends on a water test, and on genuinely chloride-rich supplies it is RO with controlled blending, not a softener.
Ice machines and post-mix
Ice is served unboiled, so its water deserves the same thinking as drinking water. Manufacturer guidance (Hoshizaki, Manitowoc) centres on NSF/ANSI 42-certified filtration: nominal 0.5 micron sediment capture and chlorine taste-and-odour reduction ahead of the machine. Scale control matters for the evaporator plates; where hardness is high, a scale-inhibiting cartridge protects the harvest cycle. For post-mix and fountain drinks, Coca-Cola's published food-service specification is the reference: zero coliforms, turbidity at or below 0.5 NTU, total chlorine at or below 0.5 mg/L, alkalinity at or below 150 mg/L, TDS at or below 500 mg/L — met in practice with certified carbon-block filtration on a compliant municipal supply.
Rule of thumb
Test the water once, properly, then match the treatment to the machine: carbon plus scale control for coffee (keep some hardness — the SCA window, not zero), chloride-driven selection for the combi oven (RO if chloride is high, and never bare softening as the fix), and certified carbon-block filtration for ice and post-mix. One shared sediment prefilter ahead of everything covers the municipal grit that arrives after every supply interruption.