A shared bathhouse with heated water and a shared laundry with tubs, a fire for heating and drying lines serve 4-8 families more cheaply than separate bathrooms, because one boiler heats water for everyone. For 15-40 people at the comfortable 50-80 L per person a day, plan 750-3,200 L of water a day, and about 5 MJ of heat to warm a 40 L bath by 30 degrees.
Part of Multi-Family Housing Design
A shared bathing and laundry facility is a room or building where several households wash themselves and their clothes, with one hot-water source and one drain.
One Boiler, One Drain, Fewer Fires
The multi-family guide says a shared bathhouse with heated water is more practical than individual bathrooms, saving water, fuel and space, and that a shared laundry needs wash tubs, a fire for heating water and drying lines. The saving is real because heating water is the largest fuel use in washing.
Worked Example: Water And Heat
Inputs: 4-8 families and 3.75-5 people each, so 15-40 people; comfortable supply of 50-80 L per person a day (the community-water guide); one bath of 40 L warmed from 10 °C to 40 °C (assumed); specific heat of water 4.186 kJ/kg·K, 1 L = 1 kg; air-dry wood at about 15 MJ/kg, the typical handbook value that Fuel Savings Measurement uses; boiler efficiency 20% (assumed).
- Water demand: 15 × 50 = 750 L to 40 × 80 = 3,200 L per day (Community Water System).
- Heat per bath: 40 × 4.186 × 30 = 5,023 kJ ≈ 5.0 MJ, or 5.0 ÷ 3.6 = 1.4 kWh.
- Wood at 100% efficiency: 5.0 ÷ 15 = 0.33 kg; at 20%: 0.33 ÷ 0.20 = 1.7 kg per bath.
- For 30 people bathing in one session: 30 × 1.7 ≈ 50 kg of wood.
The efficiency is an assumption; an open fire under a pot is often worse, a good firebox better. Measure your own with the method in the fuel-savings article.
What You Need
- A boiler or large pot with its own flue and a safe fuel supply
- A tub or washing bench, a drain and a floor that sheds water
- A greywater route to a trap and soak pit or reed bed, away from wells (Greywater Management, Greywater Recycling Systems)
- Soap and a handwashing point at the door (Hand Washing)
Method
Step 1: Site the bathhouse away from sleeping rooms and the kitchen’s fuel, with a cleaned drain downhill of every water source.
Step 2: Fit the boiler with its own chimney; keep the firebox outside the wet room or sealed from it.
Step 3: Set bathing in a rota so the boiler heats once for several users.
Step 4: Collect laundry water separately from latrine waste, and discard wash water well away from the water source (Source Protection).
Step 5: Dry laundry outdoors or in a ventilated room; damp interior air rots walls and thatch.
Common Mistakes
- No drain slope — standing water breeds mosquitoes.
- A boiler inside the wet room without a flue.
- Shared towels and cloths that spread skin infections.
Safety
Scalds, carbon monoxide and slips
Hot water scalds quickly, especially children: mix to a comfortable temperature before they enter. A water heater firebox in a closed room produces carbon monoxide; vent it to the outside. Wet floors are a major cause of falls, so use slatted or rough surfaces.
What’s Next
- Learn next: Accessibility and Aging in Place — bathing for those with limited mobility
- Combine with: Water Distribution Routes — getting water to the bathhouse