Can you tell the difference in the plumbing pipes in your home? Let’s explore Water Pipes vs. Waste Pipes

When you are trying to identify whether a pipe inside your home is a water pipe or a waste pipe, the easiest way to do so is by size. The waste system pipes are generally larger in size. Even waste pipes coming from smaller fixtures are quite a bit bigger than water pipes. Most of the water pipes have an inside diameter of ½” to 1”. In a home it is rare for a water pipe to be larger than 1”. The waste pipes are usually at least 1 ½” to 2”, which allows waste to be conveyed away from the house.

In houses that have hot water heating, it gets a little more confusing because hot water heating pipes can be either of those sizes. Often when St Paul Pipeworks plumbers go into homes they find that people are confused about which pipe does what, because they have hot water heating pipes, water pipes and waste pipes for plumbing, and gas pipes, too. Sometimes the plumber will label the exposed pipes to help the customer know what each pipe does and in what direction each is conveying water or waste.

Many of the pipes that are part of the waste drainage system are vent pipes that are hidden inside of the walls. Vent pipes provide air to the waste piping system and without them, odors are not getting carried outside. They help equalize the pressure inside of the piping, assisting the draining function. Vent pipes vary in sizes between 1 ¼” to 4”. You need to have air provided to each plumbing fixture Code for the vent piping is more complicated than for the other piping systems.

Another thing that can be confusing about some of these pipes is now there are many different things that pipes can be made of. Before 1960, all of the water piping was usually threaded, galvanized steel. The old waste piping system was mostly black cast iron pipes with some galvanized steel. Around 1965, most of the pipes for water distribution were beginning to be made of copper. There was also a short period of time where some copper was used for waste and vent piping as well.

Today there is plastic pipe available for waste, vent, and water piping. Cross-linked polyethylene, (abbreviated to PEX) is used for most of the water distribution pipes. St Paul Pipeworks plumbers use the color-coding that is available in water distribution piping because it is easy for customers to recognize. Blue pipe indicates cold water, red pipe indicates hot water.

On the waste and vent side, there are plastic pipes that are white or black and are made of different plastic materials. The white pipes are Polyvinyl Chloride (PVC) and the black are Acrylonitrile-Butadiene-Styrene (ABS). St Paul Pipeworks plumbers generally use the black ABS pipes for waste and vent over the white PVC pipes because the properties of the ABS offer slightly better quality for the customer.

If you have questions about any of your plumbing pipes or are just looking for a quality plumber in the St. Paul and Minneapolis metro area, give St Paul Pipeworks a call today.

Yours Truly,

Matthew Dettwiler

Social Media Manager


Q: What is the difference between water pipes and waste pipes?

A: Water pipes carry fresh water into your home for drinking, bathing, and cleaning, while waste pipes carry wastewater and sewage away from your home.

Q: Can water pipes and waste pipes be made of the same material?

A: Yes, water pipes and waste pipes can be made of the same material, such as PVC, copper, or cast iron. However, waste pipes may need to be thicker and more durable to withstand the pressure of wastewater and sewage.

Q: Can water and waste pipes be connected together?

A: No, water and waste pipes should not be connected together. This can cause contamination of the fresh water supply and can lead to health hazards.

Q: How can I tell if there is a problem with my water or waste pipes?

A: If you notice any leaks, drips, or strange smells coming from your pipes, it may be a sign of a problem with either your water or waste pipes. It is best to call a professional plumber to diagnose and fix the issue.

Q: How often should I have my water and waste pipes inspected?

A: It is recommended to have your water and waste pipes inspected at least once a year by a professional plumber. Regular inspections can help identify any potential problems and prevent costly repairs in the future.

Q: Can I repair my water or waste pipes on my own?

A: It is not recommended to attempt to repair your water or waste pipes on your own, as this can lead to further damage or potential health hazards. It is best to call a professional plumber to diagnose and fix the issue.

Q: What should I do if there is a leak in my water or waste pipes?

A: If you notice a leak in your water or waste pipes, turn off the water supply to your home and call a professional plumber immediately. A leak can cause significant damage and should be addressed as soon as possible.

Q: How long do water and waste pipes typically last?

A: The lifespan of water and waste pipes can vary depending on the material and usage. PVC pipes can last up to 100 years, while copper pipes can last up to 50 years. Cast iron waste pipes can last up to 75 years.

Q: Can I replace my water or waste pipes with a different material?

A: Yes, you can replace your water or waste pipes with a different material, but it is important to ensure that the new material is compatible with your plumbing system and meets local building codes.

Q: How can I prevent problems with my water and waste pipes?

A: Regular inspections and maintenance by a professional plumber can help prevent problems with your water and waste pipes. It is also important to avoid pouring grease, oil, and other substances down your drains, as these can clog your pipes and cause damage.

Water Pipes vs. Waste Pipes: What’s the difference? Ask A Plumber