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Choosing water pipes for plumbing

Last Updated Oct 19, 2017 · Written by Rob Schneider


There are reasons why plumbers must be licensed in Australia. Plumbing is more complicated than meets the untrained eye. What materials should water pipes for plumbing be made from? What are the different sizes of water pipes? When should you use a pipe of one material or size?

While there is more to plumbing than most of us know about, having some general knowledge about water pipes for plumbing can help us talk with plumbers and make more informed decisions. The following information won't make you an expert plumber, but it will help you communicate better with your licensed plumber.

  1. What Materials are Water Pipes Made From?
  2. Plumbing Pipe Sizes
  3. Choosing Water Pipes for Plumbing
  4. Garden Plumbing
  5. Putting Your Plumbing Water Pipes Together

What Materials are Water Pipes Made From?

In the past, many water pipes were made from lead, but the health hazards of lead pipes became known. Some older homes still have lead pipes. If your home has lead pipes, consider replacing them with newer, less hazardous pipes.

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Today, water pipes are generally made from plastic or copper. Some are also made from galvanised steel, cast iron or vitrified clay, but the majority of pipes are plastic. Plastic pipes can be made from a variety of types of plastic:

  • PVC (polyvinyl chloride) plastic is commonly used. It is usually used for carrying waste water
  • CPVC (chlorinated polyvinyl chloride) is often used for hot and cold water. It is also used for sprinkler systems
  • PEX (cross-linked polyethylene) and PB (polybutylene) are used for interior plumbing. They are flexible and used to carry hot and cold water. These plastics need to be coated when installed underground and don't stand up to UV rays
  • Composite pipes are made from layers of different materials. They are often used for gas reticulation

While galvanised steel was frequently used until the late 1950s, it is rarely used today. The problem with galvanised steel is that it reacts with some minerals found in water and can corrode.

Cast iron is still used, but usually in apartment buildings. It has excellent acoustic properties, which can be a benefit in apartments.

In the past, most sewerage pipes were made from vitrified clay. You can still find vitrified clay pipes, but they are being replaced with more robust PVC pipes.

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Copper pipes are still widely used. Copper has excellent antibacterial properties and is a good choice for drinking water. If it has a defect, it is that if it isn't installed correctly, it can reverberate and create a "water hammer" effect. If copper pipe is installed correctly, this isn't a problem.

Plumbing Pipe Sizes

It is far easier to understand the materials plumbing pipes are made from than the sizes of pipes you need for different applications. "Design flow" is a term plumbers use to determine the size of pipe needed for an application. The difficulty in determining the design flow is that there is no one pipe size for each application. Design flow can be different depending on:

  • The time of day
  • The type of building
  • Occupancy rates

Plumbers use formulas to work out the sizes of pipes they need, but first they need to know everything about the piping system. They need to know:

  • The water pressure
  • Pipe friction is caused by the number of bends in the pipes
  • Pipe grade (the steepness of the pipes)

Once these are used, a plumber can figure out the right size pipe for any job. Interestingly, there is not an international standard for the flow rate. In Australia, the correct flow rate is half the flow rate in Great Britain and in the United States, the flow rate is greater than in Great Britain. The reason may be that Australia has water restrictions, so a slower flow rate helps reduce water useage.

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Choosing Water Pipes for Plumbing

Knowing the materials water pipes are made from can help you choose the right pipes for your home. If you have an old home with lead pipes, you should have them replaced. If you have galvanised pipes, you can still use them, but when your pipes clog, you will need to replace them with plastic pipes. It's usually corrosion that clogs galvanised pipes and the corrosion problem can't be solved simply by using a snake to clear the pipes.

If you drink tap water, consider asking your plumber to install copper pipes. They may cost more, but because copper has antibacterial properties, you will know your water is safe for drinking.

You won't be able to choose the diameter of your pipes. While a larger diameter pipe may allow greater water pressure, plumbers have to adhere to Australian standards for pipes. Let your plumber determine the diameter of your pipes and you will know they have chosen the right size for any application.

You should never attempt to lay your own pipes. It's illegal to do so, for one thing. For another, it's too easy to make mistakes. Get quotes from licensed plumbers and choose a qualified plumber to lay any pipes for you.

Garden Plumbing

Plumbing in your garden is different from your interior plumbing. In most cases, plumbers know exactly what to do for interior plumbing. For garden plumbing, they might need more information. Hooking up an outlet for a hose is easy, but today we have more garden plumbing options.

The problem with hoses and standard sprinklers is that they cover the surface of the garden. A lot of water can go to waste due to runoff or evaporation. Many Australians are switching to more sophisticated irrigation systems. A drip irrigation system, for example can be installed at ground level or underground. More advanced systems even have moisture sensors and will turn on automatically when your lawn or garden needs watering.

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You can also save water by installing a rainwater tank and/or a greywater tank. A rainwater tank collects water from your roof. A greywater tank uses waste water. Better greywater tanks have filtration systems to filter out pollutants that could damage your plants.

While your rainwater or greywater tank supplier can install your tank for you, you'll need to hire a licensed plumber to install your pipes. Your supplier may employ a licensed plumber, who can install pipes, or you may need to hire a plumber after the tank is installed.

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Study your options when installing garden plumbing. Drip irrigation systems cost more than a hose and sprinkler, but use less water and more efficiently. Rainwater tanks and greywater tanks don't need to be unsightly cylindrical tanks that take up space in your garden. They can fit neatly against a wall and some can even be installed under your house or underground.

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Putting Your Plumbing Water Pipes Together

The information in this article won't make you a plumbing expert, but it should be enough for you to have an informed conversation with your plumber. You'll know the reason why your plumber recommends replacing lead or galvanised pipes and won't suspect them of trying to make more money from you. You will be able to talk with them about the advantages of copper piping for drinking water.

In the garden, you will be able to talk about all your water saving options. A plumber will be more than happy to install any piping you need for your drip irrigation system, rainwater tank or greywater tank. They will do an expert job and you will forget the cost after years of trouble-free use and savings on your water bill.

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