1. The Basics of Residential Plumbing Systems
A home’s plumbing structure is divided into three major parts:
Cold Water Supply System
Hot Water Supply System
Drainage and Wastewater Disposal System
These systems interconnect through fixtures such as sinks, faucets, toilets, showers, bathtubs, washing machines, and kitchen plumbing installations. The quality of plumbing design determines water pressure, flow rate, and the overall performance of household water usage.
2. Cold Water Supply System
The cold water supply system brings fresh, potable water into the home. This water can come from:
Municipal water supply
Deep tube well
Surface water treatment systems
2.1 Main Components of Cold Water Supply
The cold water distribution is typically made of PVC, CPVC, PEX, or GI pipes and includes the following parts:
Main Shutoff Valve – The control point for the entire home’s water supply.
Pressure Regulator – Ensures safe water pressure to prevent pipe or fixture damage.
Branch Lines – Smaller pipes that distribute water to fixtures such as faucets, toilets, and outdoor taps.
Service Valves – Individual shutoff valves at sinks, toilets, etc., allowing maintenance without shutting off the whole house.
2.2 How Cold Water Distribution Works
Cold water enters the house under pressure. It is directed through a network of pipes and reaches all fixtures. Some of the cold water is supplied directly to:
Toilets (for flushing)
Kitchen sinks
Outdoor hose bibs
Water heater (to be heated for the hot water system)
Cold water lines must be designed to maintain consistent pressure and avoid contamination. Backflow prevention devices are used to keep drinking water safe.
3. Hot Water Supply System
Hot water systems ensure that kitchens, bathrooms, and laundry areas receive warm or hot water at the desired temperature. This system is fueled by a water heater, which can be:
Gas water heater
Electric water heater
Solar water heater
Instant/tankless heater
3.1 How the Hot Water System Works
Cold water enters the heater and is warmed to a preset temperature. From there, it is distributed through a separate set of pipes to fixtures that require hot water.
3.2 Key Components of Hot Water Supply System
Water Heater – An insulated tank that heats and stores hot water.
Hot Water Outlet Line – Carries heated water to faucets and appliances.
Mixing Valves – Regulate temperature and prevent scalding.
Pressure Relief Valve – Protects the heater from dangerous pressure buildup.
3.3 Hot Water Plumbing Considerations
Hot water expands; therefore, expansion tanks may be necessary.
Insulated hot water pipes retain heat better, improving energy efficiency.
The length of hot water lines should be minimized to reduce heat loss and wait time.
4. Drainage and Wastewater System
The drainage system removes used water, sewage, and waste from the home through a network of drainpipes and vent pipes. Unlike water supply lines, drainage pipes rely on gravity rather than pressure.
4.1 Components of a Drainage System
a. Drain Pipes
Carry wastewater away from fixtures to the sewer line or septic tank.
b. P-Traps
U-shaped pipes under sinks, showers, and tubs that trap water to prevent sewer gases from entering the house.
c. Vent Pipes
Allow air to enter the drainage system, ensuring proper flow and preventing vacuum formation.
d. Cleanouts
Access points for clearing blockages and performing maintenance.
e. Sewer Line
The main pipe that carries all wastewater to the local sewer or septic tank.
