Working on your bathroom sink drain pipe is actually a lot simpler than working with ones in the kitchen.
However, to make sure it is going to be fully functional, you need to understand the entire drain pipe sizes and count the number of pipe units to be connected with it. Check out the following guide for bathroom sink plumbing details.
Read also: Bathroom Sink Materials Pros and Cons.
The Standard Bathroom Sink Drain Pipe Size and Setting
Every state may have different code on plumbing and it may affect the required size of the bathroom sink pipe. However, most of the bathroom sinks use 1 ¼ inch drain pipe. This bathroom sink drain size is precisely the diameter of the pipe instead of the length. For installing the plumbing, You can read in this related article, How to Install Bathroom Sink Plumbing.
When you visit a real hardware store or plumbing section, the shop assistant will mostly recommend you to use the same size. This size is actually half as big as one on your kitchen sink drain. It is actually an appropriate size for bathroom sink considering that the duty is smaller as well.
Your plumbing bathroom sink drain will throw away water mostly, or toothpaste and tiny stuffs sometimes. Therefore, bigger diameter of the pipe is actually unnecessary.
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Unlike drain pipe on the shower or tub that will be connected to two units, this sink drain pipe will be connected to only one unit on the drain line. Kitchen sink is commonly connected up to two units or three units for one with disposer.
However with vertical drain stack, this drain pipe size can handle up to two units connection well too. So if you plan to have more than one unit to be connected, stack it vertically.
The Other Bathroom Drain Pipe Size
Even though the above size is the recommended standard bathroom sink drain size, you are allowed to use other sizes too. There are actually several others alternatives available.
The first size to consider is 1 ½ inch drain pipe. This is slightly bigger than the standard yet it offers more connections as well. In horizontal stack, this drain pipe serves up to three units connected.
Meanwhile in vertical stack, it can work with up to four units connected. It is a custom size on private and public restroom for being practical for two or more sinks.
The third size is 2 inch drain pipe. This drain pipe can be connected to up to six units in horizontal stack and up to 10 units in vertical stack. This drain pipe is recommended for all models and types of washing machine. So yes, it is perfect for your laundry.
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The fourth size is 3 inch drain pipe that can be connected to 20 units in horizontal stack and 30 units in vertical stack. This is the minimum size to use for building sewer or drain pipe that is connected to the toilet.
The last size is 4 inch drain pipe that can be connected to 160 units in horizontal stack and 240 units in vertical stack. This pipe size is commonly used for sanitary drainage.
Read also: Bathroom vanity with cooper sink.
So there are many sizes available. Each offers different ability too. However for bathroom sink, you only need 1 ¼ inch drain pipe or the next size if you insist. Bigger pipe costs your more and it offers abilities you don’t actually need for a bathroom sink.