Hotel Water Demand: Litres per Room per Day

The daily total hides four different loads. Guest rooms use 120–180 L per room for showers, toilets and basin use. Food and beverage outlets use 40–70 L per room when the hotel has one all-day restaurant and a bar; banquet space and multiple restaurants push this higher. Laundry uses 60–120 L per room when operated on site. Pools and spas add 20–40 L per room for top-up, backwash and cleaning.

Laundry is the largest swing item. A 120-room hotel washing 3 kg of linen per room per day at 15–20 L per kg uses 5.4–7.2 m³/day in the laundry alone. At 60% occupancy the same laundry may run at 4 m³/day. This is why two hotels with the same room count can differ by 30–40% in water demand, and why the softener must be sized on the actual laundry load rather than on room count.

Take 300 L per room per day and 75% occupancy. Daily demand is 120 × 300 × 0.75 ÷ 1,000 = 27 m³/day. Over a 30-day month that is 810 m³; over a year, about 9,855 m³. These totals set the water purchase, the storage volume and the size of the pretreatment train, but they do not set the pipe or softener size.

For equipment, apply the peak. With a factor of 1.8 over 18 operating hours, peak flow is 27 × 1.8 ÷ 18 = 2.7 m³/h. That is the number for the softener, the main riser and the hot water plant. The drinking-water RO is sized separately: 120 rooms at 3 L per room per day need 0.36 m³/day, so a 0.5 m³/h unit with a 1 m³ tank is sufficient and leaves room for bars and meeting rooms.

Softener sizing has two checks: hydraulic flow and hardness load. At 250 ppm as CaCO₃, 27 m³/day carries 27 × 250 = 6,750 g, or 6.75 kg, of hardness per day. If the softener regenerates every three days, the resin must hold about 20.25 kg between regenerations. At a working capacity of 50 g/L, that requires roughly 405 L of resin. A 400–500 L resin charge is therefore a sensible starting point for this hotel.

Check the hydraulic side as well. A 400 L bed at a service flow of 20–30 bed volumes per hour can pass 8–12 m³/h, so the 2.7 m³/h peak is comfortable. Regeneration uses 100–150 g of salt per litre of resin, or 40–60 kg per cycle here, and produces a brine discharge that must go to drain. Confirm the salt storage space and the drain capacity before fixing the model.

Guest drinking water is a small stream compared with the building total. Plan 2–5 L per room per day for in-room kettles, ice machines, lobby dispensers and restaurant drinking water. For 120 rooms that is 0.24–0.6 m³/day. A 0.5 m³/h RO refills a 1 m³ tank in two hours, which covers the morning and evening demand without running continuously.

If the hotel has a busy bar, a brasserie or banquet service, add 30–50% to the drinking load and size storage for the dinner peak. Feed hardness above 120 ppm should be softened before the membrane; otherwise use antiscalant and accept shorter cleaning intervals. Keep the permeate conductivity below 10 µS/cm for consistent coffee and ice, and install UV at 30–40 mJ/cm² after storage.

The standard range fits a full-service business or city hotel. Four other types need their own planning figure, and using the standard range for them leads to either an undersized laundry softener or an oversized drinking-water plant.

Treat the figure as a water balance, not a label. A 200-room conference hotel at 300 L uses 60 m³/day, but if 30% of rooms are suites with in-room laundry and the banquet kitchen runs two shifts, the real figure may exceed 400 L per room. Build the estimate from the outlets that exist, then compare the result with the 250–400 L benchmark; a large gap usually points to a missing load or an unrealistic occupancy assumption.

A hotel is a living building: occupancy, restaurant concepts and laundry contracts change. The design should be based on measurements and operating assumptions that are written down, not on a room count alone.