Coffee Shop Water Filter System — Hardness, Alkalinity and Flavour

Coffee is mostly water, so the water recipe matters as much as the beans. Three parameters drive the cup: hardness, alkalinity and chlorine. Hardness above roughly 100 ppm as CaCO₃ scales espresso boilers, steam wands and level probes, causing temperature drift and service calls. Alkalinity above roughly 70 ppm buffers the acids that give coffee its brightness, so the cup tastes flat, chalky or muddy.

Chlorine and chloramine are the third problem. They react with coffee aromatics and produce medicinal, plastic or papery notes that no grind adjustment can fix. High TDS adds a salty or mineral edge, while water that is too pure tastes hollow and can corrode copper and brass in the machine. The goal is not zero minerals; it is a stable, repeatable mineral profile.

Different brew methods also need different water. Espresso machines recirculate water in a boiler and are sensitive to scale; filter brewers and iced coffee use water once and are more sensitive to alkalinity and chlorine. A shop that serves both may need two points of use with different blending settings rather than one compromise. Milk steaming also concentrates minerals in the steam boiler, so the steam circuit deserves the same water quality as the brew water.

Plan 0.1–0.2 m³ per day per 100 cups. The range covers espresso, filter coffee, tea, drinking water and the water lost to backflushing and steam. Add 20–30% for cleaning, pitcher rinsing and milk station use. A shop serving 300 cups per day therefore needs roughly 0.4–0.8 m³/day, not the 0.3–0.6 m³ the cup count alone suggests. Cup count is a rough guide only; a shop with heavy iced-coffee sales uses more water per cup than one serving mostly espresso, because ice and larger serve volumes add draw.

Peak flow is set by the espresso machine, not by daily cups. A single-group machine typically fills and backflushes at 0.25–0.5 m³/h; a two-group machine with a high-volume brew bar may draw 0.5–1.0 m³/h. Size the softener or RO at or above that peak, and keep a 0.5–1.0 m³ storage tank if the machine has a boiler fill pump that cycles frequently. If the shop uses reverse osmosis, install a pressure gauge and a sample point after the blend so the barista can verify the recipe at the start of each shift.

Most coffee systems fit under the counter: allow 0.8 × 0.6 m and 1.6 m height for a twin softener or a 0.5–1 m³/h RO with a small tank. Provide a 220 V socket, a drain for regeneration and concentrate, and 2–4 bar inlet pressure. Keep the brine tank accessible for salt bags and place it within 3 m of the valve head.

Run separate food-grade lines to the espresso machine, brew bar and ice machine, with a blending valve on the espresso line so the barista can adjust TDS without changing the whole system. Avoid copper and brass downstream of RO, because low-mineral water is aggressive; use PEX, stainless or food-grade composite. Fit isolation valves and a sampling point at each machine so a water sample can be taken without disconnecting the line. Label the blend setting and record it in the bar log, so a new opener does not reset it by accident.