What Are the Three Types of Plumbing Systems?

A Complete Guide for Homeowners in London, Ontario

When you think of the plumbing in your home — the water flowing from the tap, the toilet flushing, the drain in the shower — you’re really tapping into three major plumbing systems that work together quietly, behind the walls and under the floor. Understanding these systems helps you recognise issues earlier, plan upgrades wisely, and choose a reliable plumbing partner when needed.

In this article we’ll break down:

1. What each system is.

2. How it works (especially in Ontario/Canada).

3. Why it matters for homeowners.

4. How BEST Drainage can help.

1. Potable Water Supply System

What it is

This system is responsible for safely delivering fresh, clean water into your home for drinking, cooking, washing and bathing. It starts from the water service line (from the municipal supply or well) and branches out to fixtures like faucets, showers, toilets, washing machines.

How it works (Ontario context)

In London and across Ontario, the water arrives at a regulated pressure (often 40–80 psi) and passes through a main shut-off valve near the entry point (see diagram Canadian Home Inspection Services). From there:

• Cold supply lines branch off to fixtures.

• A hot-water line is fed from the water heater.

• Pipes are sized and installed per the National Plumbing Code of Canada 2020 / Ontario Building Code.

• Materials commonly used: copper, PEX, CPVC.

Why it matters

• If pressure is low, or you see discoloured water, you may have a supply‐system issue.

• Proper installation prevents leaks, contamination, and costly water damage.

• In a cold climate like Southwestern Ontario, freeze-protection and pipe insulation matter.

Homeowner tip

Know the location of your main shut-off valve. In renovations, ask if the existing supply system meets current code and uses modern materials.

2. Drainage, Waste & Vent (DWV) System

What it is

Often abbreviated DWV, this system carries used water and waste out from your home, and allows air to enter so that drains can flow freely. It includes: drain pipes, waste stacks, vent pipes leading up through the roof. Wikipedia

How it works in your home

• Wastewater from toilets, sinks, showers travels by gravity into the sanitary sewer or septic system.

• Vent stacks equalise air pressure and prevent sewer gases entering the home.

• The Ontario Building Code references the requirements for pipe slopes, trap seals, venting minimums.

Why it matters

• Poor venting = slow drains, gurgling, foul odours.

• Incorrect slope or undersized drain = backups, flooding, expensive repairs.

• Older homes may have outdated materials (cast iron, lead) which can degrade.

Homeowner tip

If you hear “gurgle” when you flush a toilet, have frequent backups, or smell sewer gas, ask for a camera-inspection of your DWV system. It could save you major cost down the road.

3. Storm and Non-Potable Water Systems (Optional third type)

What it is

While less discussed, this third type often refers to systems managing rainwater, ground-water or non-potable water (like greywater) — separating it from the potable supply and sanitary sewer. Some articles, for instance, list three systems: potable supply, sewage, drainage/runoff. TRADESAFE+1

Why it matters in London, Ontario

• With increasing heavy-rain events and basement flooding risk, proper storm drainage is crucial.

• Systems may include sump pumps, exterior downspout drainage, backwater valves.

• If improperly connected (storm + sanitary mixed), it can create surcharge risks and violate municipal codes.

Homeowner tip

Ensure your downspouts and sump discharge are directed away from your foundation. If you plan a garden or shed, consider how the system manages run-off.

Integrating the Three Systems: Why It Matters

When your home’s plumbing works smoothly, you’ll likely not notice the separate systems. But when issues arise — leaks, backups, foul odours, flooding — understanding which system is affected helps you make the right call.

• The potable supply system: affects water quality/pressure — immediate health and comfort impact.

• The DWV (drain/waste/vent) system: can lead to functional failure (toilets/backing up) or indoor-environment issues (odours).

• The storm/non-potable system: often external, but failures can lead to foundation damage or basement flooding.

How BEST Plumbing & Drainage Helps You in London, Ontario

At BEST Plumbing and Drainage Contractors, we specialise in all aspects of plumbing, drainage and sewer work for homeowners across London and surrounding Southwestern Ontario. Whether you’re dealing with slow drains, sump pump installation, or old plumbing replacement, our team of licensed technologists and plumbers knows how the systems above inter-connect.

Our services include:

• Supply-line inspection and replacement (copper → PEX upgrades)

• Camera inspection of drain/waste/vent systems

• Storm-drainage solutions, sump pump installs, backwater-valve retrofits

• Helping ensure your home complies with the Ontario Building Code and local municipal requirements

When you call us, you’ll get clear explanation of which of the three systems is causing your issue — saving time, cost and confusion.

FAQs

Q1: Can I mix materials in the potable system (e.g., copper and PEX)?
Yes — when done correctly and per code. PEX is now very common in Ontario homes due to its flexibility and ease of installation.

Q2: My basement keeps flooding — is that the storm system or sanitary drain that’s the problem?
Often a storm/run-off issue (third system) — but if the sanitary sewer becomes overloaded (or backs up), it could be the DWV system. A professional inspection will determine the cause.

Q3: Does the drainage system include my sump pump?
The sump pump typically sits within the storm/run-off system (third type) rather than the main waste‐water (DWV) system.

Q4: Are there any changes in code I should be aware of?
Yes — the National Plumbing Code of Canada 2020 (and its provincial equivalents like the Ontario Building Code) include updated rules for water conservation, non-potable water reuse, venting, and materials.

Summary

Understanding the three plumbing systems in your home helps you keep everything functioning smoothly:

• Potable water supply (bringing clean water in)

• DWV system (taking waste & used water out)

• Storm / non-potable system (managing run-off and external drainage)

If you’re in the London-Ontario area and dealing with plumbing, drainage or sewer issues, get in touch with BEST Drainage — we’ll identify which system is involved, explain your options clearly, and help you take the right next steps.

Why Homeowners Trust BEST Plumbing and Drainage Contractors

For over 50 years, BEST Plumbing and Drainage Contractors has been serving homeowners across London and Southwestern Ontario with reliable, professional plumbing solutions. Our team brings decades of technical expertise and hands-on experience to every project — from emergency repairs to complete system replacements.

We understand how important it is to have a plumbing system you can depend on. That’s why we stand behind our work with comprehensive warranties, clear communication, and transparent pricing — no hidden surprises. Whether it’s your water supply, drainage, or venting system, our licensed professionals diagnose issues accurately and provide solutions built to last.

When you choose BEST Plumbing and Drainage Contractors, you’re choosing a company that combines old-fashioned service values with modern plumbing technology. From camera inspections and trenchless drain repairs to water line replacements and sump pump installations, we’re committed to quality, safety, and customer satisfaction every step of the way.

Contact BEST Plumbing and Drainage Contractors today to schedule a service or inspection. Experience why London homeowners have trusted our team for five decades — and discover the difference true professionalism makes.