There are five main diameters for drain snakes, these are: 1/4″, 5/16″, 3/8″, 1/2″ and 9/16″. Each size has a recommended range of drain pipe diameters they are suitable for.
An easy way to classify and remember these is to separate them into small, medium, large and extra-large categories.
What pipe sizes can they be used with?
Small
The 1/4″ (6 mm) diameter drain snake is advised for pipes that are 1 1/4″ (31.75 mm) and 1 1/2″ (38.1 mm) in diameter.
This is the most common household drain snake and is used for sinks, baths, showers and some drains.
Medium
Both the 5/16″ (7.94 mm) and 3/8″ (9.53 mm) snakes are considered medium sized. They are most suitable for use in 2″ (50.8 mm) drain pipes.
A 3/8″ snake is usually found on toilet augers.
Large
Large snakes have a diameter of 1/2″ (12.7 mm) and are recommended for 3″ (76.2 mm) (usually external) drain pipes.
Extra-large
9/16″ (14.29 mm) diameter drain snakes are extra-large and designed for use on 4″ (101.6 mm) and 5″ (127 mm) drain pipes.
These are usually the sizes reserved for external drain pipes.
It is important to use the correct size drain snake on the appropriate drain pipe because small snakes can become tangled in large drain pipes and large snakes can damage small pipes.
It is difficult to determine what diameter pipes you have, the best things to check are plumbing regulations and local building codes to give you the best idea. Also remember to take in to consideration when your property was built and if the pipes have ever been redone.