Water supply, drainage and sanitation
Water supply. Mains water or a pump fills a tank on the roof. Gravity sends water down pipes to the taps. Pressure grows with depth: p = ρgh (ρ = 1000 kg/m³, g = 9.8 m/s²). So 10 m of water gives about 98 000 Pa ≈ 1 bar. Very tall buildings use booster pumps and break-tanks at middle floors.
Drainage. Used water (from sinks, showers, toilets) goes into waste pipes that slope gently, about 1 in 40, so it flows by gravity. Under each fitting is a trap: a U-bend that keeps a little water as a seal against smells and germs. A vent pipe up to the roof lets air in so flowing water does not suck the trap dry. Rainwater has its own pipes; it can be stored and reused (rainwater harvesting).
Heating, ventilation and air-conditioning (HVAC)
Ventilation replaces stale air with fresh air. Windows on opposite walls give cross-ventilation; exhaust fans remove steam and smells from kitchens and toilets.
An air conditioner is a heat pump. A refrigerant gas takes in heat inside (the indoor coil gets cold) and gives it out outside (the outdoor unit gets hot). It also removes moisture. In cold places the same idea, run in reverse, heats a room. Good insulation and shading cut the heat that enters, so less cooling is needed.
Electrical and communication installations
Power enters through the meter, which measures energy in kWh. Then it reaches the distribution board, where each circuit (lights, sockets, AC) has a miniature circuit breaker (MCB) that switches off if too much current flows. An RCD/RCCB switches off if current leaks, protecting people from shock. The earth wire (green or green-yellow) carries leakage safely into the ground.
Communication services include internet (copper or optical fibre cables), phone, TV, intercom, CCTV and alarm wiring.
Fire protection, lifts and energy saving
Fire protection: smoke and heat detectors, alarms, sprinklers (a glass bulb bursts at about 68 °C and lets water spray), extinguishers, hose reels, fire doors and clear escape routes with exit signs. In a fire, never use the lift.
Conveyance: lifts (elevators) and escalators. A lift car hangs on steel ropes over a pulley; a counterweight on the other side balances it, so the motor lifts only the difference.
Energy saving: energy = power × time (kWh). LED lamps use about one sixth of the power of old bulbs. Setting the AC 1 °C higher saves about 6%. Solar panels, insulation, shading, motion sensors and efficient pumps cut use further.
Installation materials
- Water pipes: CPVC, PPR (joined by heat), copper, galvanised steel. Must be safe for drinking water and handle hot water where needed.
- Drain pipes: PVC/uPVC, cast iron. Smooth inside, with traps and cleaning points.
- Cables: copper wire with PVC insulation; thicker wire for larger current (for example 2.5 mm² for sockets, 4–6 mm² for AC). Run inside conduits.
- Ducts: galvanised steel sheet with insulation for air.
- Fittings: valves, taps, switches, sockets, all matched to the job and standards.
Key formulas and definitions
- p = ρgh (water pressure at depth h)
- 1 bar = 100 000 Pa ≈ 10 m of water
- Energy (kWh) = power (kW) × time (h)
- Cost = energy (kWh) × rate per kWh
- Drain slope = fall ÷ run (e.g. 1 in 40)
Worked examples
1. A tap is 12 m below the water level in a roof tank. Find the water pressure at the tap (ρ = 1000 kg/m³, g = 9.8 m/s²).
p = ρgh = 1000 × 9.8 × 12 = 117 600 Pa ≈ 1.18 bar.
2. A drain pipe 8 m long falls at 1 in 40. How much lower is the far end?
fall = 8 ÷ 40 = 0.2 m = 20 cm.
3. A 1.5 kW air conditioner runs 8 h a day for 30 days. Find the energy used.
E = 1.5 × 8 × 30 = 360 kWh.
4. Six 60 W bulbs are replaced by six 9 W LEDs, used 6 h a day for 30 days. How many kWh are saved?
Saving per lamp = 51 W. Total = 6 × 51 = 306 W = 0.306 kW. Energy = 0.306 × 6 × 30 = 55.08 kWh.
5. At ₹8 per kWh, what money does the LED change above save each month?
55.08 × 8 ≈ ₹441.
6. Why must a lift have a counterweight about equal to the car plus half the usual load?
Then the motor only lifts the small difference in weight in either direction, so it needs much less power and the ropes stay tight.
Common mistakes
- Thinking an AC creates cold. It moves heat from inside to outside.
- Laying drain pipes flat or too steep. Flat pipes block; very steep pipes let water run off and leave solids behind.
- Removing the earth wire or using a thin cable for a big load. Both are fire and shock risks.
- Using the lift during a fire. Always use the stairs.