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How To Measure Bathroom Sink Drain Size; DIY Plumbing


How To Measure Bathroom Sink Drain Size

Installing a sink or any other part of your house that deals with water is crucial, and getting it wrong can be disastrous. 

If you have a leaky sink, you could end up with damaged or slippery floors that could cost a lot to repair.

To avoid these issues, you need to get the installation right. You must get a suitable drain pipe to fit into the sink drain, and to do this; you need to know how to measure the size of your drain. Let us get into the details and help you figure this out;

How To Measure Bathroom Sink Drain Size

You can use a tape measure to measure the sin drain from the middle to get an accurate diameter. The best way to know your drain size is to check the manufacturer’s manual since it has the exact size in the description. 

1 5/8 inches and 1.5 inches are standard sizes, but one and a quarter is the most common and the best choice for most people.

How To Measure Pipe Diameter 

Getting the correct pipe size for your house is crucial in the construction process. You need to get the correct pipe size to fit into the sink and the wall so you don’t have leaks after several months of using the sink.

The sizes of pipes have different properties depending on the material used in the pipe. Different materials have different thicknesses, so the outer size might be the same, but the interior diameter is different.

You can download the pipe measuring tool on the internet and use it to measure diameters for pipes, whether iron, copper, or galvanized. You need to download the tool, print it out then cut the paper into a thin workable size.

If you want to measure a pipe and you don’t want to use a ruler, this will take all the guesswork out of the equation. 

The tool is a sort of scale with marks with different colors. The dashes and colors represent the type of pipe you are measuring.

At the bottom of the paper is a solid black arrow, which is the most critical part of the scale. You need to wrap the piece of paper around your pipe to see where the black line lands on your dotted lines, which is the size of the pipe you have.

Wrap the paper onto the pipe with the blank side making contact with the pipe so you can see the arrow. Take the piece of paper around, and the line closest to the solid black line is your pipe’s size.

Use the dashes depending on the type of pipe you want to measure; if it is an iron pipe, you will need to use the dots for iron. 

The lines will not always be exact since you will need to twist the paper a little bit, but it will always be clear which size. 

If you have other tools that can do the job, feel free to use them. You can use a standard ruler and take the measurements in centimeters, then convert them and round them off to get a standard pipe size. 

How To Install A Drain In A Bathroom Sink

After knowing your drain size, you need to figure out how to install the pipes and get everything running once more. 

This is a guide to installing bathroom sink drains, and they are more straightforward, so you can do them yourself. 

This guide is vital for people installing pipes for the first time or those that need to repair a leaking system. 

The drain collar could crack over time, or the metal cap could rust, and you will need to replace the whole assembly to fix this problem.

You will need a drain, channel lock pliers, plumber’s putty, cloth, and plastic container for this process. 

First, we will discuss how to remove a sink drain to follow the process from where it involves you if you are doing a first-time installation.

1. Disconnect the drain

When working with a sink, there is a chance there will always be some water in the system, so you need to drain it first before going on. Place the plastic container underneath the P-trap and drain water out of the pipes.

You need this to prevent an unnecessary mess under your sink, and you will have an easier time working in a dry environment rather than a wet one.

Use the channel lock pliers to loosen and unscrew the nut at the back of the trap, then unscrew the second nut and remove the trap. 

If you have a P-trap without the drain, you can loosen it and push it out of the way without dismantling everything.

2. Remove the drain

Use the channel lock pliers to open the nut at the base of the drain; you can only access this nut from underneath the sink. Remove the rubber gasket, then pull the drain out from the top of the sink.

Use a piece of cloth and scraper to clean off all the plumber’s putty around the sinkhole, so it holds better when you add a new layer.

3. Install the new drain

This is the first step for those that will be installing the sink drain for the first time. Take a small amount of plumber’s putty, roll it into a stick, then place it around the drain. Make sure you put a tick enough amount all around to prevent leakages.

You don’t need to work about putting in too much putty since you can remove it after the installation

Push the drain into the sinkhole and press it firmly into place, ensuring you don’t leave any gaps on the sides for water to leak. 

Slide the rubber gasket onto the shaft and tighten the nut with your hand before using the pliers to tighten the nut into place. 

At this point, the drain will squeeze out any excess putty, and you can clean it off with a piece of cloth.

4. Reconnect the drain

Reinsert the nut at the bottom of the drain, then reconnect the P-trap and hand tighten the nuts at both ends of the p-trap. Hand-tighten the p-trap release nut since it can leak, and your sink will be ready to use.

Test the faucet and let the water run while the drain is open and closed to see any leaks. 

The Types Of Pipes You Need In Your House

Plumbing is one of the most crucial parts of a house, and it can mess up the comfort and structure of your house if you dint get it right. 

Today we will go over the most common sizes of pipes and where you are supposed to use them in your house;

1. The half-inch pressure line

This is the smallest pipe you will use in plumbing around your house, and you can use CPVC or PEX for this. This pipe will go up to the fixture in all your plumbing systems

This means that the pipes will have to get to the taps, faucets, and showerheads to deliver water at high pressure. 

It is also convenient to install all around the house since it won’t mess with the walls or décor.

2. Three-quarter-inch water line

You can use CPVC or PEX for this as well, and this is the line that will be feeding water to all your pressure lines. 

It also needs to be small enough to keep high pressure on the water to go up in the pressure lines and come out of your fixtures.

3. Drain lines

The smallest option you get for drain lines is the inch and a half PVC pipe, and there are many other styles and materials you can choose to use. 

These pipes don’t need to have a lot of pressure since they will be carrying water from high points in the sinks to the sewage systems. 

However, they have to be large since they don’t always have clean water, and most of the time, there are solids in the system. A thin pipe would get a blockage relatively quickly, so increasing the diameter reduces the chances of a blockage.

4. Toilet and shower drain

The shower and the toilet will have even bigger pipes ranging from 3 inch PVC pipe to 4-inch pipe. 

The toilet needs to have the biggest pipe to ensure you don’t get blockages as they pass many solid items into the sewer line. 

For the shower, you need to ensure that the drain takes out more water than the showerhead releases so you dint end up standing in a pool of water in the middle of your shower.


Drains and pipes are a crucial part of any house, and you need to take a lot of interest in getting the correct sizes of drains for your house.

Measuring your bathroom sink drain is a simple matter that you can accomplish with a ruler and a keen eye. If you want more accuracy, you can look at the manufacturers’ manual to see the size and get the guesswork out.

Jacob Lindsey

Jacob is a home remodeling guru having worked over 15 years in construction in Reno, NV, mainly focused on home renovations. He likes taking ideas from his clients and making them a reality.

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