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Home Plumbing Basics for Homeowners

Written by Mike S. Avelar, CPI

Understanding how your home’s plumbing works helps you spot problems early and keep your water system safe. Plumbing includes the pipes, fixtures, appliances, and equipment that deliver clean water and remove wastewater from your home.

As home inspectors, our main goal is to confirm that a home has:

  • A safe and reliable water supply
  • Proper drainage
  • Fixtures and equipment that do not contaminate potable water

Why Plumbing Systems Matter

A properly designed plumbing system serves two essential purposes:

  • Supplying hot and cold potable water
  • Safely removing wastewater into a public or private disposal system

Water Supply: How Water Gets to Your Home

Municipal vs. Well Water

If you live in an urban area, your water likely comes from the municipality. Rural homes often rely on drilled or dug wells. Both systems use service piping to bring water into the home. Many homes and business in rural areas however, use drilled or dug wells to supply water to one or more dwellings.

Service Piping Basics

Service piping runs from the water main or well pump to the house. It should:

  • Be as short as possible
  • Have minimal bends to maintain pressure
  • Be buried below the frost line to prevent freezing (about 1.22m in Ottawa)

Modern urban homes typically use a ¾” service pipe with around 40 psi.

What You Should NOT See

Certain materials or connections are red flags:

  • Cement or concrete joints
  • Glue between different types of plastic
  • Female threaded PVC fittings

Important Shutoff Valves

Several shutoff valves protect your home and allow maintenance:

  • Corporation Stop: Buried under the road; used during construction or emergencies.
  • Curb Stop: Easier to access; often used for nonpayment or flooding issues.
  • Meter Stops: Two valves that isolate the meter and the home for maintenance or replacement.

Meter stop valves can wear out quickly if used too often.

Hot and Cold Water Distribution

Once water enters the home, it travels through a network of hot and cold supply lines. These lines are typically hung from the basement or crawlspace ceiling and supported with proper hangers to prevent sagging.

Lead Solder in Older Homes

Centennial homes may have copper piping joined with lead solder. If you live in an older home, consider testing your water for lead.

Hot and Cold Line Spacing

Hot and cold pipes should be about 6 inches apart unless the hot line is insulated. This prevents heat transfer to the cold line.

Where Water Lines Are Found
  • Homes with basements: lines run overhead
  • Homes without basements: lines may run in crawlspaces or under slabs

  • Some homes have lines in the attic, which increases the risk of freezing and leaks that can damage interior finishes. In some cases, they may be in the attic space; this arrangement can lead to problems due to freezing pipes, condensation…

Common Plumbing Materials

PVC

Durable plastic used for low‑pressure drains, sprinkler systems, and water service lines. Potential health hazards exist.

CPVC

Yellow in colour, suitable for hot and cold potable water, and good for corrosive water conditions.

Copper

Highly durable and recognizable. Should not be used where water pH is 6.5 or lower unless treated. Comes in grades M, L, and K.

Galvanized Steel

Lifespan of about 40 years. Corrodes easily, restricting flow. Mixing galvanized steel with brass or copper accelerates corrosion and can interfere with electrical grounding.

PEX

Flexible, freeze‑resistant (not freeze‑proof), and excellent for new builds or replacing old piping.

Kitec

Used from 1990–2005; recalled due to rapid corrosion and water damage.

Poly & Polybutylene

Poly is used for cold water but cracks with age. Polybutylene (PB) reacts poorly with some water treatment chemicals and can burst over time.

Valves You May See in a Home

Valves allow safe control of the water system. Common types include:

  • Shutoff Valves: Allow servicing without draining the entire system.
  • Check Valves: Prevent backflow.
  • Flow Control Valves: Maintain uniform flow.
  • Relief Valves: Release excess pressure.
  • Pressure Reducing Valves: Lower pressure so thinner piping can be used.
  • Altitude Valves: Prevent hot water tank overflow.
  • Foot Valves: Found in wells to prevent backflow.
  • Frost‑Proof Hose Bibs & Hydrants: Designed to prevent freezing; hydrants may be prohibited in some areas due to contamination risks. However, due to the possibility of contaminating local water sources, these may be prohibited in your area.

Heating Water

Most homes use hot water tanks powered by electricity, oil, natural gas, or solid fuel. All tanks should have a visible temperature‑pressure relief (TPR) valve with a discharge pipe ending no more than 6 inches from the floor.

If the TPR valve is releasing pressure, contact a plumber or rental company immediately.

Tankless Water Heaters

Tankless systems heat water only when needed, last longer than traditional tanks, and are easier to repair. Proper sizing is essential.

Wastewater and Drainage

Wastewater flows into the sanitary drainage system, which typically uses 4” pipes. Materials include cast iron, copper, clay, plastic, and sometimes lead. In Ottawa, ABS is the standard. The best choices today are PVC or ABS depending on your geographical area, here in Ottawa it is ABS.

Plumbing Traps

Traps create a water seal that blocks sewer gases, which can be harmful or explosive. The P‑trap is the most common.

Venting

Proper venting prevents siphoning, protects trap seals, and ensures smooth drainage. Rare traps like full S‑traps require careful venting.

Water Quality Concerns

Water with an imbalanced pH can corrode copper piping. Testing and treatment may be required to maintain safe drinking water.