DWV stands for Drain, Waste and Vent. But not all pipes are equal!
Today’s wholesale plumbing supply industry offers a huge range of quality plumbing products needed to to tackle almost every type of tough Aussie installation or repair.
There are also many near identical or similar materials, sizes and fittings. You can’t afford to make a mistake. You need to buy the right part for the job.
In this article, we’ll take you through the difference between PVC pipes and DWV pipes, and their individual application.
So you get it right first time.
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What is a PVC pipe and when do you use it?
PVC stands for Polyvinyl Chloride. It’s a rigid and durable form of white-coloured plastic pipe made by combining the chemical liquids of chlorine and ethylene. PVC pipe is typically available from both electrical and plumbing product suppliers.
Advantages of using PVC pipes
A key advantage, particularly in the Aussie environment, is its chemical properties which make PVC pipe:
- Resistant to corrosion and weathering – from air salts, soil acids, and oil contaminants. Typically used in underground systems.
- Non-toxic – and safe for many standard types of applications.
- Lightweight for installing– particularly in high-rise apartments or office tower blocks.
- Easy and straightforward to handle – using solvent welding or adhesives.
- Resilient and long-lasting – cost and maintenance-free.
Common residential and commercial uses of PVC pipes
Typical uses of PVC pipe include:
- Water transportation
- Liquid transportation – including chemicals, heating and cooling fluids, ultra-pure liquids and compressed air.
- Waste disposal – easy and clean maintenance.
- Electrical wiring conduit – non conductive, flame and UV resistant.
What is a DWV PVC pipe: and why you must use the correct PVC pipe to avoid disaster
A DWV PVC pipe is:
- Not made to withstand water pressure
It’s the reason why this class of PVC pipe is assigned as DWV – for the use only of simply transporting Drain, Waste, and Vent water or liquids.
How does it work?
A DWV PVC pipe simply uses gravity in a downward flow along the pipe. Because there’s no pressure in the pipeline, there’s also no stress placed upon the structure of the pipe itself.
This means a DWV PVC pipe is:
- Made with thinner walls
A key advantage is:
- No pressure testing is needed when installing
But the downside is:
- Similarity in size of a DWV pipe end fitting and threading to a Schedule 40 pipe and fittings
This could cause confusion and pose a real disaster risk when ordering at a local trade plumbing suppliers.
It’s essential NOT to inadvertently join a DWV pipe and fittings to Schedule 40 pipe and fittings.
What is a Schedule 40 pipe?
A Schedule 40 pipe refers to the thickness of its walls.
And as defined by its “schedule”, the amount of pounds per square inch (PSI) a pipe or fitting can handle.
While both types of pipe are made from the same unplasticised PVC (PVC-U), Schedule 40 PVC pipes are made with thicker walls designed to:
- Withstand low pressure applications
Compared to DWV piping, which has thinner walls and are not made for carrying water or liquids under pressure.
Advantages of a Schedule 40 PVC pipe
- Ideal for residential / domestic plumbing and irrigation purposes
- A nominal 2 inch (.154 inch inner diameter / 2.375 inch outer diameter) pipe can handle up to 280 PSI (pressure per square inch)
- Usually identified as white – or sometimes, grey – in colour
- Low cost
For industrial, manufacturing and chemical applications, the more expensive Schedule 80 PVC pipe is usually installed.
Its thicker walls (.218 inch inner diameter / 2.375 inch outer diameter) can handle up to 400 PSI.
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Pipe end-fitting and thread – what to look out for
To avoid a plumbing disaster it’s essential to check the different pipe ends and their threads, which can often look identical. Or can be either threaded or socket (also known as “slip”).
DWV pipes and standard PVC pipes:
- SAME size
- SAME socket (“slip”) end fitting
- SAME threading
Schedule 40 PVC pipes:
- Threaded OR socket (“slip”) end fitting
A DVW pipe end socket (“slip”) end fitting is called a “hub” and is usually less pronounced than a Schedule 40 end fitting.
Another vital detail is knowing the difference between BSP and NPT threads.
BSP versus NPT threads
BSP pipe threads
BSP stands for British Standard Pipe, which is a typical thread type available at Australian wholesale plumbing distributors.
Please Note: thread sizes conform to industry classification rather than actual pipe diameters.
Example: Trade Size: 2 = Actual External Diameter: 2.347 inches.
Plus there are two types of BSP threads:
- BSPP – Female and male
- BSPT – Parallel female and tapered male
Both thread types have the same pitch angle of 55 degrees with rounded thread edges.
NPT pipe threads
NPT stands for National Pipe Thread – a US standard for tapered threads and fittings.
Also known as:
- MPT , MNPT or NPT (M) – male external threads
- FPT, FNPT or NPT(F) – female internal threads
As with BSP threads, sizes are also determined by an industry standard in place of actual pipe diameter.
Example: Trade Size: 2 = Actual External Diameter: 2.75 inches
NPT threads have a pitch angle of 60 degrees with flattened thread edges.
Another way to check is by counting threads
Example: Trade Size: 2 =
- 11.5 threads per inch (NPT/NPS)
- 11 threads per inch (BSP)
In a nutshell …
A DWV PVC pipe is only used for transporting Drain, Waste, and Vent water or liquids because it is not made to withstand water pressure.
When a low pressure is required to actively transport water or liquids, a Schedule 40 PVC pipe is made with thicker walls for a safe and secure water flow.
DWV pipes, standard PVC pipes and Schedule 40 pipes all have identical threaded OR socket (“slip”) end fittings. However, a DVW pipe end socket and fitting hub is usually less pronounced than a Schedule 40 end fitting.
Commonly available PVC pipes usually have BSP or NPT /NPS threads, which differ slightly by size, number of threads and pitch angle.
FAQs
Q: What is a DWV pipe used for?
A: To remove waste water, including from WCs, bathtubs/showers, sinks, washing machines and dishwaters.
Q: Can DWV pipe be used underground?
A: Yes. DWV pipes are corrosion-resistant to soil acids, and oil contaminants, and are commonly used in underground systems.
Q: What is the ISO code for a PVC pipe?
A: ISO 4439:1979 is the current standard, first published in 1979 and confirmed in 2020.
Q: What is the Australian standard for PVC pipe?
A: AS/NZS 1477 – which covers Series 1 (coloured white) and Series 2 (coloured light blue) metric size, and both compatible with the outside diameter of Australian cast and ductile iron pipes.
Q: DWV vs stormwater pipe?
A: Both can be used as they are interchangeable. DWV is stronger than a stormwater pipe and their 90 degree elbows are considered to be more efficient.
CLICK HERE for our DVW Master range of low pressure PVC fittings
Need more advice on what DWV / PVC pipe you need for your project?
