PVC Pipe Sizes - Both pipes are 4 inches in diameter, but the schedule 40 white one has much thicker sidewalls than the green SDR-35 pipe. If you're trying to draw plumbing plans, you better consult with a master plumber like me. (C) Copyright 2021 Tim Carter
PVC Pipe Sizes - Thickness Matters
QUESTION #1: Tim, I went to buy some plastic drain pipe and after looking at all the types my head started to hurt. I decided to leave the store and do some research. I’ve got several projects where I need a plastic pipe. I need to add a bathroom in a room addition, I need to replace old cracked clay downspout drain lines, and I want to install one of the linear french drains I saw on your website to dry out my basement. Can you give me a quick tutorial on the sizes and types of plastic pipe the average homeowner might use around her/his home? Lori M., Richmond, VA
It’s fairly easy to get flummoxed like Lori did as there are so many different plastic pipes. Just ten days ago, I installed a somewhat special plastic pipe to vent my daughter’s new high-efficiency boiler. It was made from polypropylene and can withstand much higher temperatures than standard PVC that most plumbers might use.
Watch this video of this amazing boiler or water heater vent pipe:
It’s very important to realize that there are lots of different plastic pipes that you might use and the chemistry of them is quite complex. I’m just going to stick with the most basic ones you might run into or may be required to use by your local inspectors.
CLICK or TAP HERE to get FREE BIDS from local plumbers who know plastic pipe sizes.
What are the Most Common Plastic Pipes?
PVC and ABS plastic pipes are perhaps the most common ones you’ll run into when it comes to drainage pipes. Water supply lines are another ball of wax and I’m not even going to try to confuse you further about those!
What's the Difference Between ABS and PVC Pipe?
ABS and PVC pipe look similar, but ABS can perform at a wider range of high and low temperatures. ABS pipe has a higher impact strength than PVC pipe. ABS is about 20 percent more expensive than PVC pipe.
What are the Common PVC Pipe Sizes?
The most common PVC pipe sizes you’d use around your home would be:
- 1.5 - inch
- 2-inch
- 3-inch
- 4-inch
I used PVC for decades and it’s a fantastic material.
What are the Different Sizes Used For?
The 1.5-inch size is used to capture water that might flow out of a kitchen sink, a bathroom vanity, or a tub. The 2-inch pipe is commonly used to drain a shower stall or washing machine and it may be used as a vertical stack for a kitchen sink.
A 3-inch pipe is what’s used in homes to pipe toilets. The 4-inch pipe is used as the building drain under floors or in crawlspaces to transport all the wastewater from a home out to the septic tank or sewer. The 4-inch pipe is also used as a vertical drain stack in a home. Always do this if two or more bathrooms drain into the same stack. Plumbers and inspectors use pipe-sizing tables to tell them what size pipe needs to be used where.
The wye fitting at the bottom of the photo is a 4x3 wye. There are two bathrooms that converge at this point and the pipe you see leaving the bottom of the photo is 4-inch no-hub cast iron. I installed this pipe in my daughter's new home on Mt. Desert Island in Maine in the winter of 2019.
Does the Pipe Thickness Vary?
The wall thickness of the plastic pipes does vary. Plastic plumbing drainpipes for a typical home are schedule 40. This is a thicker material and is designed to withstand decades of use and punishment from metal drain-cleaning snakes.
What is Cellular PVC Pipe?
Cellular PVC pipe looks just like schedule-40 PVC and it's dimensions are the same, but it's lighter in weight. It's not as strong as schedule 40 and it takes far less pressure to burst it if you're trying to build something that will requires the storage of compressed air. Here's an example of a tool made from PVC that uses compressed air. ALWAYS use schedule 40 to build one:
Be sure your local plumbing inspector allows cellular PVC to be used on your job.
What PVC Pipe is Used for Exterior House Drains?
SDR-35 is a popular PVC pipe used for exterior house drains. It's strong and it can withstand far more crushing force than some of the flimsy thin-wall plastic pipes you may see at a home center. SDR-35 is commonly used by plumbers for the drain line that extends from a house to a septic tank or a city sewer.
Give SDR-35 PVC a good look for the outside drain lines you want to install. It’s a strong pipe and the sidewalls are thinner than the schedule 40 pipe. I’ve used the SDR-35 pipe for decades with fantastic success. The last house I built for my family had over 120 feet of 6-inch SDR-35 pipe that connected my house to the city sewer.
A lighter-weight plastic pipe with holes in it will work fine for that buried linear french drain. Be sure the two rows of holes aim down. Don’t make the mistake and point them up to the sky as they may get plugged with small stones as you cover the pipe with washed gravel.
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