Sediment and carbon filtration

Strips particulate, chlorine and the taste and odour compounds that travel with it, so the water tastes of nothing before the coffee is added to it.

Two stages doing two unrelated jobs, and they are routinely treated as one. The sediment stage is mechanical: a depth or pleated medium that physically captures particles larger than its rating, protecting everything behind it from abrasion, blocked solenoids and a scoured pump. The carbon stage is not filtration at all — it is ADSORPTION. Chlorine and organic taste and odour molecules stick to the enormous internal surface area of activated carbon as water passes through it, and two consequences follow that operators miss constantly. The first: adsorption is a finite-capacity process. The medium fills up. When it is full the water still flows, still looks clean, still leaves no visible sign of anything, and is no longer being treated — which is why capacity is rated in volume rather than in months, and why a calendar-only change schedule is a schedule for a bar whose volume nobody counted. The second, and the reason this entry exists in a category about scale: CARBON DOES NOTHING TO HARDNESS. Calcium and magnesium pass straight through it, unchanged and undiminished. A carbon filter protects the TASTE of the water; it does not protect the BOILER. A bar can have genuinely excellent-tasting water from a carbon cartridge and still be destroying an element month by month, and nothing in the cup will warn anybody. Removing chlorine also removes a disinfectant residual, which is precisely the point for flavour and worth understanding for hygiene: everything downstream of the carbon is now an unprotected surface, so a line that stagnates over a closed weekend is a line worth flushing before service.

• Fit carbon as the baseline on every bar, and never as the answer to hardness. It belongs on the line because untreated chlorine ruins the taste of everything and because it protects the membrane or resin of whatever sits behind it. It does not touch calcium and magnesium, so a carbon-only chain on a hard supply is a bar with lovely water and a dying element. What the supply test said is what decides whether anything else is needed.
• Size the cartridge on VOLUME against your own draw, not on the calendar and not on the size of the venue. Capacity is rated in litres passed, and litres passed depends on drink mix, ice, tea and how many machines share the line — a small bar with an ice machine and a boiler on the same cartridge can outrun a larger bar without them.
• Check flow at PEAK SIMULTANEOUS demand, not against one machine's figure. The espresso machine refilling while the boiler refills while the ice machine calls is the real load, and it happens at exactly the moment nobody can afford a slow refill. A cartridge chosen on capacity alone can be right on volume and wrong on flow.
• Treat pressure drop as an operational specification and not a footnote. Restriction rises as the cartridge loads, so the flow you commissioned is the best flow the system will ever have. If the machines are marginal on day one they will be worse by the change interval.
• Insist on a head with an isolating valve you can reach and a flow meter you can read without moving anything. A cartridge that requires the counter to be pulled out to be changed is a cartridge that gets changed late, and every argument in this category depends on it being changed on time.
• Decide deliberately WHICH lines are filtered. The espresso machine and the hot water boiler are obvious. The ice machine is the one that gets forgotten, and ice is a food that goes straight into the glass — untreated ice will carry the taste of the building into every cold drink on the menu, and scale will do to the ice machine's evaporator what it does to a boiler.
• Put the change in the maintenance schedule with a volume, an owner and a date, and log a reading at each change. A carbon cartridge gives no warning: it does not slow, it does not discolour the water, it simply stops adsorbing. The schedule is the only mechanism that catches it.
• Confirm the connection, the available supply pressure and any backflow requirement with a licensed plumber before ordering, and let the local authority govern. What a site can deliver in pressure is a property of the building, not of the cartridge, and it decides whether the chain you have drawn is buildable at all.