A kitchen waste pipe is typically 1 1/2 inches (40mm) in diameter, but 2 inches is often recommended for better flow, especially with dishwashers or heavy use, connecting down from the sink's tailpiece. While 1 1/2 inch is common for basic sinks, using 2-inch piping from the sink trap down to the main drain reduces clogs from food and grease.
the simple answer is that basin wastes are 1¼” BSP (32mm), whereas bath and kitchen sink wastes are 1½” BSP (40mm).
Waste pipe sizes
40mm: Normally used for kitchen sinks, showers and baths. 50mm: A large pipe commonly suited to commercial applications or connecting multiple waste pipes to a single flowing system.
The most common kitchen sink drain size is 1 ½ inch. This is also a common size for larger bathroom sinks and other sinks that hold a larger volume of water and need a larger drainage capacity. Sinks that get more than average use may also be good candidates for this mid-range drain pipe size to keep the water flowing.
The most common size among consumers is 32mm in diameter, but before purchasing, we recommend you check with your qualified plumber, who can advise you precisely what size the waste outlet needs to be.
32mm nominal internal bore (outside diameter is bigger at approx 34.5mm) plastic waste pipe x 1 foot, available in white, black or grey. This size is popular for bathroom basin wastes.
As mentioned, kitchen sinks use a 1 1/2 inch pipe, while bathrooms often utilize 1 1/4 inch pipes. This difference helps in managing the flow of water, preventing backups that can occur in smaller pipes.
Kitchen Sink Drain Sizes
Whether you have a single or double basin sink, the standard, universal drain hole diameter is 3-½”, this size ensures compatibility with other drain assemblies or garbage disposals.
3/8 Inch Supply Line
Common Use: Often used for bathroom sink water lines or kitchen sink water lines with a moderate flow rate.
Kitchen sink P-Traps come in 1-1/2” standard size, while bathroom sinks use P-Traps of 1-1/4” standard size. The traps also come in different material types such as propylene, ABS, brass (chrome-plated or natural), and PVC.
40 mm waste pipes are used in areas where higher volumes of water will be entering the system such as baths, showers and kitchen sinks.
40mm waste system is the common size for bath and kitchen sink installation.
40 mm (1.1/2") BS EN 1451-1 plastic pipe. Do not solvent weld. The actual pipe size is approximately 41 mm o.d. x 36 mm i.d..
A 32mm waste pipe is typically used for appliances that present low volumes of water to the system (e.g. small hand basins), while 40mm is normally used for kitchen sinks, showers and baths. 50mm, on the other hand, is large to suit commercial applications or connect multiple waste pipes to a single flowing system.
1" pipe actually has an outside diameter of 33.4mm. 1" pipes or spigot fittings (measuring 33.4mm outer diameter) will slot inside one end of this socket to be solvent welded, and 32mm pipes or spigot fittings will slot inside the other end.
All basin wastes are the same size at 11/4" or 32mm. All bath /sink wastes are 1½" or 40mm BSP (British Standard Pipe).
The 135 rule of plumbing refers to the placement of drain line cleanouts, which are used to clear any clogs and keep the drains functional. According to the 135 degree rule of plumbing, a cleanout must be present every 100 feet of drainage line and for each cumulative change in pipe direction that exceeds 135 degrees.
9/16”-24UNEF IS THE SAME as 3/8" compression.
Standard pipe size for kitchen sinks: The Uniform Plumbing Code (UPC) requires a minimum 1.5-inch drain pipe, but 2 inches is commonly used for higher water volume.
Pipe Size. According to foundation repair experts, a typical French drain system in a residential home has a four-inch diameter. But if the area experiences a high volume of water, it might be suitable to install six or eight-inch pipes.
What Is Standard About Kitchen Drains? In the United States, the standard kitchen sink drain hole diameter is 3.5 inches (90mm). This size accommodates most common basket strainers and garbage disposal units, which are designed with this specification in mind.
The exact plug size will then depend on what kind of fitting the drain has, but 1 ¾ inches is usually considered the 'standard' size for modern plugs. Most hardware and DIY stores will offer a range of plugs to fit that size, so you can choose whatever style or colour plug that you wish.