Office Water Filter System — Central RO, Loop and Dispensers

Office water use is small but spread over many points: pantries, meeting rooms, reception, a gym and sometimes a staff canteen. The usual arrangement is a bottled-water cooler on each floor, which means bottle handling, storage space, plastic waste and a cleaning routine that is easy to postpone. Water quality depends on the supplier and on how clean the cooler is, not on the building supply.

Where a building has a central filter, the problems shift to the distribution loop. Long branches to meeting rooms, floors with low occupancy, and weekend shutdowns create stagnant water. Coffee machines and kettles scale when hardness is high, and scale on the boiler changes extraction and increases descaling frequency. Chlorine keeps water safe in the mains but spoils the taste of coffee and tea. In older buildings, the incoming line may also carry rust and sediment after maintenance work, which plugs aerators and cartridge filters before any water quality problem reaches the tap.

The design question is therefore not only what to remove, but where to treat. Treating at one central point is easier to maintain and gives consistent quality; treating at each dispenser avoids long loops but multiplies cartridges and service visits. Most offices above about 100 staff are better served by a central plant with a loop.

A central system treats water once, stores it, and circulates it through a loop to dispensers on each floor. Maintenance happens in one plant room, water quality is uniform, and the dispensers are simple taps with a UV point. A point-of-use system puts a small RO or carbon filter under each sink. It avoids loop piping and landlord negotiations, but every unit needs its own cartridges, power, drain and service visit. The loop should be designed with balance valves so the top floor receives the same flow as the lowest floor; otherwise the far dispensers run slow and users revert to bottled water.

The crossover is around 80–120 staff or three or more floors. Below that, point-of-use units are simpler and avoid long runs of unused pipe. Above it, a central loop usually has lower maintenance effort per litre and better control of stagnation, because the loop can be flushed and monitored as one system. Hybrid layouts are common: central RO for pantries, point-of-use carbon for a remote reception or gym.

A central plant for 100–300 staff needs about 2.0 × 1.5 m, with 2.2 m clear height and 0.8 m service access. Provide a floor drain, a power point, and a lockable room because the RO, tank and UV are service equipment. Smaller point-of-use units need 0.5 × 0.6 m under the sink, a 220 V socket and a drain connection. Allow space to remove the membrane housings and to store a spare tank or cartridge set; a plant room packed too tightly after installation becomes expensive to service.

Power is 220 V single phase up to 1 m³/h and 380 V three phase for larger units. Inlet pressure should be 2–4 bar; below 1.5 bar add a booster. Route the loop in food-grade PEX or stainless steel, insulate it, and install isolation valves and drain points at each floor so a section can be flushed without shutting the building. Keep dispensers at 900–1,000 mm above finished floor and allow wheelchair access.