The first step in any renovation is water and electrical work. Mistakes here are incredibly costly to fix later. How do you choose wire gauge? How should circuits be divided? Should water pipes run along the ceiling or the floor? This article explains it all clearly, based on standards and principles.

Water & Electrical Renovation Avoidance Guide: Wire Gauge & Circuit Planning

1. Electrical Circuit Basics

Wire Gauge Selection

Copper Wire Cross-Sectional Area & Current Capacity

Cross-Section	Safe Current Capacity	Application
1.5mm²	10A (2200W)	Lighting circuits
2.5mm²	16A (3500W)	General outlet circuits
4mm²	25A (5500W)	Kitchen / AC circuits
6mm²	32A (7000W)	Central AC / Instant water heater
10mm²	50A (11000W)	Main incoming line

Circuit Planning Principles

Divide Circuits by Function

Main Breaker → 
  Lighting Circuit (1.5mm²)
  General Outlet Circuit (2.5mm²)
  Kitchen Outlet Circuit (4mm²)
  Bathroom Outlet Circuit (4mm²)
  AC Circuit 1 (4mm²)
  AC Circuit 2 (4mm²)
  Dedicated Refrigerator Circuit (2.5mm²)

Key Principles

Dedicated Refrigerator Circuit: When you turn off the main breaker while away, the fridge stays on.
Dedicated Circuits for High-Power Appliances: AC, water heater, oven each get their own circuit.
Separate Kitchen Circuit: The kitchen has many high-power appliances.
Separate Bathroom Circuit: High safety requirements in a damp environment.

Circuit Breaker Selection

Circuit Type	Breaker Spec	GFCI (RCD)
Main Breaker	2P 40-63A	As needed
Lighting	1P 10A	Not required
General Outlets	1P+N 16A	Required
Kitchen Outlets	1P+N 20A	Required
Bathroom	1P+N 20A	Required
AC	1P 20-25A	Not required (required for floor-standing units)

⚠️ Avoidance Tip: The breaker's rated current MUST be greater than the wire's safe current capacity. Otherwise, the wire will overheat and burn before the breaker trips! Correct relationship: Breaker current ≤ Wire safe current capacity.

2. Outlet Layout Planning

Outlet Quantity Reference by Area

Living Room

TV wall: 4-5 (TV, set-top box, soundbar, router, spare)
Both sides of sofa: 2 each (phone charging, lamp, floor fan)
AC: 1 (16A dedicated)
Spare: 1-2 (vacuum cleaner, etc.)

Bedroom

Both sides of bed: 2 each (phone, lamp, humidifier)
TV/Computer: 2-3
AC: 1
Spare: 1

Kitchen

Countertop: 4-6 (rice cooker, microwave, oven, blender)
Under sink: 2 (water purifier, garbage disposal)
Range hood: 1
Refrigerator: 1 (dedicated circuit)

Bathroom

Near vanity: 1-2 (hair dryer, electric toothbrush)
Near toilet: 1 (smart toilet seat)
Spare: 1

Outlet Height Reference

General outlets: 30cm from floor
Bedside outlets: 70cm from floor (above nightstand)
Switches: 130cm from floor
Kitchen countertop outlets: 30cm above countertop
AC outlets: 180-200cm from floor

3. Water Pipe Routing

Ceiling vs. Floor Routing

Comparison	Ceiling Routing	Floor Routing
Leak Detection	Early (drips down directly)	Late (seeps to floor below)
Repair Cost	Low (remove ceiling)	High (remove floor tiles)
Installation Cost	High (more materials)	Low
Insulation	Requires insulation wrap	Floor provides natural insulation
Noise	Possible water flow sound	None

Recommendation: Run pipes on the ceiling in bathrooms/kitchens; floor routing is acceptable elsewhere. Regardless of method, a pressure test is mandatory after completion.

Pipe Materials

Material	Features	Application
PPR Pipe	High temperature resistance, heat-fusion connection	Mainstream hot/cold water pipe
PE-RT Pipe	Good flexibility	Underfloor heating pipe
Stainless Steel Pipe	Safest, most expensive	High-end renovation
Copper Pipe	Antibacterial, expensive	Localized use

PPR Pipe Specifications

Spec	Outer Diameter	Wall Thickness	Application
S3.2	20mm	3.4mm	Hot water pipe (PN25)
S2.5	20mm	4.1mm	High-pressure hot water pipe
S5	20mm	2.0mm	Cold water pipe (PN10)

Recommendation: Use hot water pipe spec (S3.2) for both hot and cold water lines. The thicker wall is safer, and the price difference is minimal.

Pressure Test Standards

Test pressure: Working pressure × 1.5, and ≥ 0.6MPa
Hold time: ≥ 30 minutes
Pressure drop: ≤ 0.05MPa
No leaks = Pass

4. Separating High & Low Voltage Lines

Wiring Rules

Distance between high and low voltage lines: ≥ 30cm
At crossing points: Wrap with tin foil for shielding
High and low voltage lines cannot share the same conduit or channel
Keep the low voltage panel and high voltage panel at a distance

Low Voltage Planning

Ethernet cable: Start with Cat6a, reserve fiber optic
TV cable: Coaxial cable / Ethernet cable as substitute
Phone line: Optional (no longer essential in the smartphone era)

5. Inspection Checklist

Electrical Inspection

Number of circuits matches the design
Wire gauge matches the circuit
Breaker specs are correct
GFCI (RCD) function test (press test button to trip)
No exposed wire terminals
Insulation resistance test ≥ 0.5MΩ
Outlet wiring is correct (left neutral, right live, top ground)
Switch controls the live wire

Water Pipe Inspection

Pressure test passed
Distance between hot and cold water pipes ≥ 15cm
Hot water pipe wrapped with insulation
Pipes are securely fastened
Valves open and close smoothly
Drainage is smooth and unobstructed
P-traps are correctly installed

6. Common Pitfalls to Avoid

❌ Not keeping a diagram of the water/electrical layout → Later drilling can puncture pipes or wires
❌ Not enough kitchen outlets → At least 4 on the countertop
❌ Bathroom outlets are not waterproof → Must use splash-proof covers
❌ Not pressure-testing the water pipes → Always watch the pressure test yourself
❌ Overfilling conduits with wires → Wire cross-section area must not exceed 40% of the conduit's cross-section area
❌ Running high and low voltage lines in the same channel → Severe signal interference

💡 Summary: Water and electrical work is the foundation of any renovation. The core principles are: "thick enough wire gauge, enough circuits, enough outlets, and pressure-test the water pipes." A dedicated refrigerator circuit is a detail many people overlook, and it's incredibly costly to change later. Remember: take photos of everything after the water and electrical work is done. They will save your life when you need to drill into the walls later.