This home plumbing diagram illustrates how your home should be plumbed.

The different colour lines in this drawing represent the various plumbing pipes used.

  • The blue lines are the fresh water supply entering the home.
  • The red lines are the hot water supply after it has left the hot water tank.
  • The black lines are waste pipes (grey water and sewage).
  • The yellow lines are the venting pipes; these enable air and gasses to escape the system.

There are two basic systems to your home’s plumbing: the one that gets the clean water in and another that takes the dirty water away. They are connected in the middle by your fixtures: sinks, showers, toilets, and appliances like washing machines and dishwashers. Once it’s in your home, your clean water supply gets divided into the cold water and hot water systems.

Your waste water network is also made of two systems: the pipes that take the water away and the venting pipes that keep sewer gas from getting into your home.

Together, they keep your home’s water supply flowing safely for your health and comfort.

Head’s up! Have you received a letter from SLWC? If so, here’s everything you need to know about sewer and water service repairs.

How Your Home’s Plumbing Works

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Your plumbing can make all kinds of noises, but if they’re high-pitched or loud you may have a problem that needs fixing. This guide describes the most common noises and what causes them.

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Your Fresh Water Supply

How water gets into your house

Clean water enters your house through one pipe called the “main water supply line” or “service line”. The size of this pipe will depend on your exact system, but it will be the largest pipe in your supply network. Pipes get smaller in diameter as they get closer to your fixtures to ensure there’s enough pressure and flow to supply multiple fixtures at once.

There are two potential sources for your water supply:

  • Water on your property from a well, pond or nearby river or stream.
  • A city’s municipal system.

These days, getting water from your own property is generally done through a deep well, which is generally sourced from an aquifer 35 feet deep or deeper. It is possible to have shallower wells, but they are more subject to change in drinkability (from surface contaminants) and volume (from rainfall or droughts). While there are lots of exceptions, water from a deep well is generally drinkable.

Usually it’s only cottages that are supplied by water from a nearby pond, lake or river. This water is generally not considered safe to drink, but it’s safe to bathe in. Personal water supplies almost always need to be treated for hardness, or excess minerals that can build up in your plumbing over time.

Municipal water supplies are taken from large bodies of water nearby, or can be from large wells. Municipal supplies are almost always treated properly to ensure it is safe to drink (an extremely rare exception would be the infamous Walkerton supply that was tainted in 2000) and looks clear. Most municipalities, however, don’t treat water for hardness.

Pressure and Flow

Water needs a bit of a push to keep moving through your pipes. On personal properties, that pressure is supplied by the pump from the well or lake. Cities have a lot of water to push, and so often make use of tall water towers. It’s more efficient to pump water straight up to a central tower, and then let gravity help push it down and then out over the surrounding areas. Some cities make use of pumping stations as well.

The pipes inside your home are designed to withstand pressures from 25 – 80 PSI (pounds per square inch). If there’s too little, water won’t flow. If there’s too much pressure, it can cause banging noises and puts stress on the joints between pipes, especially as they age. There’s nothing inside your home that controls the pressure – it’s completely reliant on the pressure created by the incoming supply.

Cold Water Supply

Cold water flows from the service line to every fixture in your home. It’s generally run in the most efficient manner possible, with fixtures grouped in a central column from floor to floor. This not only helps save on pipe materials costs, but also ensures smooth continuous flow.

If your plumbing was run in a more spaghetti-like fashion throughout the house, there would be more of a chance that flow would become more restricted.

Hot Water Supply

Running pipes in as straight a line as possible becomes even more important with hot water. The more pipe there is, the more heat will be lost. It also means that you don’t have to run the water longer than necessary before your get the right temperature, which of course wastes water.

In truth, the only reason to have a hot water supply is comfort. Even in the summer, we often use a little bit of hot water in our showers and baths. (For example, you don’t actually need hot water in your washing machine. Hot water does not actually make your clothes any cleaner. It’s probably just a holdover from the days when we washed our clothes by hand, and having your arms in freezing water for hours at a time would have been really unpleasant.)

The usual way to heat your water is using a hot water tank, but these days tankless or on-demand water heaters are becoming more popular. They’re great for families who want to make sure no one has to take a cold shower.

There’s a happy medium to the temperature you should set on your water heater. If it’s too hot, you’ll waste energy because more heat will escape through the pipes and the tank. You also risk scalding yourself (if you don’t have a scald prevention valve installed.

If your tank temperature is too low, you can risk the growth of harmful bacteria like the one that causes legionnaire’s disease. You should be great if you keep it set to 60 C/ 140 F.


If you turn on a tap and you don’t get any water, it means there’s a blockage somewhere – or a leak. It could be anywhere in your house, or possibly a problem with the supply outside your home. It’s important to perform regular maintenance on your plumbing system to prevent future issues.

Your Waste Water System

The drain pipes that carry your dirty water away get larger the further away from a fixture they are. This is to ensure good flow even if several people are running taps or flushing toilets at the same time. A pipe under your sink will start at about 1 ½” in diameter, but will connect to a pipe about 4” in diameter by the time it leaves your house. The pipe that connects your home to the city’s sewer system is called a “sewer lateral” and can be 5-6” in diameter.

Having pipes get bigger over the course of the run is also really important to help prevent blockages. The inside of your plumbing gets coated with a layer of scum over time, and can also have hair and other things inside at various points.

There’s a whole science between maintaining the right flow to prevent as much debris as possible from being left behind. The water and anything in the water have to go at a similar speed. If the water is draining too slow or too fast, it will leave hair, dirt or toilet paper behind. The angle of the waste water pipe plays a key role.

Breathing for your Plumbing: Traps and Vents


You may have noticed a u-shaped bend on the pipe beneath your sink. This is a really necessary feature. This bend stays full of water, and it’s this little pool of water that prevent sewer gas from entering your home. Not only is sewer gas really smelly, it can also be dangerous because it can carry microbes in its moisture. It is also carcinogenic long term.


Your plumbing system needs to breathe in order to function properly. Having a set of venting pipes that go through your roof prevents a vacuum from forming that would prevent waste water draining away.

To illustrate how this works, try putting a drinking straw in a glass of your favourite drink. If you put your finger over the top of the straw and then lift the straw out of the glass, you’ll notice you take some of the drink with you. The water stays in the straw and doesn’t leak out because you’ve created a vacuum seal using the air in the straw. If you remove your finger, your drink pours out again.

Without venting, the traps in your plumbing would work in the same way as having your finger cover the straw. But you actually want the water to drain away, and you need the traps to block sewer gas. The answer is to create another way to relive the vacuum – and that’s a set of air pipes that vent to your roof.

Anywhere you have a trap, you need a vent pipe. The venting pipe network starts small in diameter close to the traps, and gets larger the closer it is to the exit point for your home. The size of the venting pipes are precisely chosen to make sure air is sucked out at the right rate (bigger = faster, smaller = slower). It’s really important to get this right when the plumbing system for a home is designed, or water won’t drain away.

Climate, specifically winter temperatures, also play a role in vent pipe diameters. The pipe has to be large enough to prevent the moist air from condensing at the exit point, freezing, and thereby blocking the pipe.

The vent placement on the roof of a house has to be done so that sewer gas won’t go in any open windows.

The Cleanout

Home owners should take care not to block the waste line cleanout (that’s where the pipe leaves your home). If there’s ever a problem, your plumber will need to get in there to inspect and work in the area. We get in there both to figure out if there’s a problem somewhere in the household plumbing or if there’s and issue in the sewer lateral (most commonly it’s tree roots).

You shouldn’t try to open the cleanout yourself unless you really know what you’re doing. Not only is the cleanout disgusting, but it’s technically a biohazard. Bacteria of all kinds –including dangerous ones – thrive in the moist environment, and so do insects. Plumbers know to use protective equipment like face shields and steel-fingered gloves to prevent exposure to dangerous micro-organisms like hepatitis and HIV/AIDS.

Your Plumbing Deserves Professional Care

Our plumbing system is truly a modern miracle, developed over the centuries as advances were made. Most people don’t know or appreciate the wonderful design of a modern plumbing system. Now that you know, maybe you’ll enjoy turning on that tap even more next time. And if you run into problems with your plumbing, we encourage you to contact the professionals at Out of This World Plumbing.