Are All Bathroom Sink Drains The Same Size?

Perhaps you decided it’s time for a bathroom upgrade, which includes the sink. You tossed out the entire dated sink and its drain assembly and respective plumbing, so now it’s time to purchase replacements. You might’ve bought a new sink, so now it comes down to purchasing the appropriate drain and plumbing. 

However, when you go to the hardware store, you notice there are a few different drain sizes available. So, which one should you buy? Aren’t bathroom sink drains all the same size? Well, no, they’re not all the same size, so the correct drain assembly hinges on your sink. Here’s what you need to know. 

Are Sink Drain Sizes Standard?

There isn’t a standard sink drain size, although there are a few common sizes. Some sources state the most common size for a bathroom sink drain hole is 1 ¼ inches, while others claim the standard is 1 ½ inches. Generally, these two are the most common sizes. 

That said, you might come across sinks with a 1 ⅝-inch drain hole. Due to the variation, you need to be sure you purchase the correct size drain assembly. Some manufacturers sell their sinks with the appropriate drain assemblies, so you won’t need to worry about this part. If that’s not the case, double-check sizing before purchasing a drain assembly. 

How Do I Know What Size Drain Do I Need?

Most of the time, newly-purchased sinks have instructions that will indicate the proper drain size. So, you can refer to the owner’s manual or instructions for the correct drain size. However, if you don’t have the paperwork (we get it), that’s okay. 

You’ll need to measure the drain of the sink directly across the center of the drain to measure the diameter of the circle. Once you have the measurement, you can determine what size drain is appropriate for the sink. 

It’s important to understand that your sink drain needs to be the same size or smaller than the drain hole. So, if your sink has a 1 ¼-inch drain hole, it needs to have a 1 ¼-inch drain hole or smaller. Or, if the sink features a 1 ½-inch drain hole, it is compatible with a drain that is 1 ½ inches or 1 ¼ inches.

The reasoning behind the “same size or smaller” rule is due to the measurement of the drain. This measurement applies to the part of the drain that fits into the hole of the sink. Each drain comes with a drain flange, which is the part that rests on the sink and covers the hole. This part is much larger than the threaded portion, so a slightly smaller drain will work. 

Aside from the drain itself, the rest of the plumbing and piping needs to fit the sink drain. You’ll need pipes the same size as the drain hole. If it’s a 1 ½-inch drain hole, use a 1 ½-inch pipe. You can find bathroom plumbing in varying sizes at your local hardware and home improvement stores. 

When you purchase plumbing for the sink, ensure the pipes are the same size, as you don’t want to mix and match (or it can get complicated).

Take Note Of Local Housing Code

As you browse for a new sink and drain assembly, remember to consider your local housing code. Many states and local governments outline codes that are more stringent than the national standards for drain sizing. So, be sure to check local codes before you buy replacement plumbing and drain assemblies.

This doesn’t mean you need to overhaul your entire home with new plumbing – old plumbing can stay. That said, any replacement plumbing needs to meet the most recent local codes. If you can’t find these codes, check with the local building authority or a professional plumber. 

Are All Bathroom Sink Drain Pipes The Same Size?

As mentioned earlier, the drain pipes beneath your bathroom sink should match the drain size. So, if your bathroom sink drain is 1 ½ inches, it should have a 1 ½-inch drain pipe. Again, you can find piping at your local hardware or home improvement store, but remember to stick with the same size plumbing (otherwise, you’ll have to add extra parts to connect the pipes).

Frequently Asked Questions (FAQs)

Do I Need A Sink Drain With Overflow?

The overflow feature on a sink helps prevent the sink from overflowing. These sinks have a small opening near the top of the sink that lets air flow into the drain when the sink is full of water. This helps the sink drain faster when you open the drain, which helps prevent overflow. 

If your sink has an overflow feature, you need to buy a drain with an overflow cutout. These drains feature a small hole drilled in the upper threaded portion of the drain. This allows overflow water (and air for faster draining) to enter the drainage pipe. Be sure to purchase the correct drain type, as this is crucial for proper sink and drain function. 

What Type Of Drain Should I Buy?

Several types of drains are designed for bathroom sinks that come in varying materials, finishes, sizes, and brands. Pop-up drains are one of the most common drain types and open and close via a lever on the back of the faucet. However, you can also find other variations, including push drains, which open and close via a simple push of your finger that engages the mechanism.

Leave a Comment