Are Toilet Tanks Interchangeable? Universal Tank Guide

If you need to replace a damaged or cracked tank, then you may run into a common question: Are toilet tanks universal (i.e. standard sizes)?

Toilet tanks are not universal. Toilet tank sizes vary depending on which of the four flushing systems you have; dual flush, gravity, pressure-assisted, or vacuum-assisted. Generally, toilet tank sizes are universal within these flushing system categories, unless you have a custom toilet. 

Further on in this article, you will find information to help you find, purchase, and install a new toilet tank that is the perfect fit for your toilet. Let’s get to it!

Are Toilet Tanks Universal?

In short, types of toilet tanks are not universal. Three things affect if a toilet tank will fit or not. Those three things are the type of flushing system, the toilet tank brand, and the size of the toilet tank.

These things can all vary but if you match all three to your old toilet tank, you should be able to find replacement parts that fit.

Let’s talk more about each of these three things and then we’ll talk about how you can get the information you need to get a perfectly fitting new tank.

Type of Flushing System

To understand what type of tank you have, first, you need to know the kind of flushing system you have. The four flushing systems are dual flush, gravity flush, pressure assisted, and vacuum assisted.

1. Dual Flush Toilet

Are toilet tanks interchangeable

In this type of toilet, the flushing mechanism is found on the top of the tank in the form of two buttons, one for low flow intended for liquid waste, and one for high flow intended for solid waste.

This type of flushing system allows you to control how much water is being used and can help increase your home’s water efficiency.

You can tell if you have this type of tank if you have two flushing options

So, if you have a toilet that has two flushing options, then make sure that you look for tanks that are compatible with dual flush toilets when you go shopping for a replacement tank.

2. Gravity Toilet

Gravity toilets are probably the model of toilet that is most frequently used in homes today, so there’s a pretty good chance that this is the type of toilet you have.

Gravity toilets flush by using gravity (hence the name) to facilitate the movement of water from the bowl into the sewage system. 

This type of toilet has a rubber flapper inside the toilet tank. To tell if you have this type of tank, take the lid off your toilet tank and look for the rubber flapper usually in the middle of the tank.

If you have this setup, then you have a gravity-flush toilet.

3. Pressure-Assisted Toilet

Pressure-assisted toilet tanks, while similar in build to a gravity toilet, have a mechanism in the tank that pushes the water down the pipe into the bowl and then through to the sewer. 

Instead of your tank being filled with water with a flapper on the bottom of the tank, pressure-assisted toilet tanks will have a device that will look like a block that fills most of the tank.

This builds up some pressure and then uses this pressure to give your flush an extra push.

4. Vacuum-Assisted Toilet

A vacuum-assisted toilet tank is a relatively new development in the toilet world. It’s similar in function to the pressure-assisted toilet but instead of pushing, it pulls.

A device inside the toilet tank builds up a pressure differential that allows the toilet to suck or vacuum the water out of the toilet bowl.

Pretty crazy, right? It’s hard to tell the difference between this type of tank and a pressure-assisted toilet, but since they’re relatively new, they’re still fairly uncommon.

If you’re not sure if you have a vacuum-assisted or a pressure-assisted toilet, you can try looking up the brand and model number online. We’ll talk about how to do that later on.

Toilet Brand

Are toilet tanks universal sizes

Now that you know what kind of flushing system you have, you need to know your toilet brand. Different manufacturers will have different dimensions and plumbing hookups.

This is usually pretty easy to find, a brand label or mark should be on your toilet right in between the toilet seat bolts.

Some of the labels may be the same color as the toilet tank which can make them hard to see, the toilets in my current house are like that, I tried to take a picture to show you but you can’t read the brand in the photo!

Size of Tank

Last but not least, you need to know the size of your tank.

If your new tank isn’t the same size as your old tank, the holes to connect with your plumbing system and toilet bowl may not be in the right place.

You can determine the size of your tank by either googling the brand and serial number of your toilet or by measuring your tank manually.

The next section will walk you through how to do both of those things, let’s get going.

How To Determine Your Toilet Tank Type

There are two ways you can figure out what kind of toilet tank you need. You can find your brand and serial number or you can manually measure your tank. Let’s go over each one.

By Brand and Serial Number

The first thing you need to do is figure out what brand of toilet you have. You can find this either inside the lid of the tank or down right behind the bowl like below:

Are toilet tanks universal sizes

After you have the brand, you also want to know the serial number. I found the serial number for my toilet on the inside of the toilet tank here:

Some toilets will have the serial number listed on the bottom of the toilet tank lid. If you don’t see the model number in the toilet tank, check the lid for it as well.

Now that you have the brand and serial number, you can Google it. If you have a recent model of toilet you’ll likely be able to find a replacement toilet tank online.

If the model is old or discontinued it might be tough to find. In this case, it may be easier to buy a whole new toilet with a tank and toilet bowl together.

You can also go into a local hardware store or home improvement store and ask an associate for help.

If you tell them the brand name and the serial number, they’ll likely be able to help you find the right replacement tank or a new toilet if no replacement tank will fit.

Manually Measuring the Tank

If you’re not confident that you’ll be able to easily find a perfectly fitting replacement tank for your toilet or you can’t find the serial number, then you may want to take a few measurements.

To do this, you’ll need to grab a measuring tape, a pen, and some paper.

You will need to measure the following distances:

  • Depth of the tank
  • The length of the tank
  • The width of the tank

You’ll also want to measure the pipes and fixtures. When you shop for a new tank, you will need to make sure the pipes and fixtures you have fit. Otherwise, you will need to replace those as well.

Now, what about the sizes of the tank bolts (and bolt holes)?

Are Toilet Tank Bolt Sizes Standard?

Just as the tanks vary, so do the bolts and bolt-hole sizes.

Similar-sized toilets may share bolt and hole sizes while a custom toilet may use unique sizes.

But usually, the size of a bolt is 1/4th inch or 5/16th inch.

The size of the bolt hole will match the size of the bolt. When you go to take measurements of the tank, look at the bolts. If they are not too eroded, you’ll be able to read the size right off the markings on the bolts.

Side note: If you also intend to replace your toilet seat, then you’ll need to consider toilet seat sizes as well.

How Do You Install a New Toilet Tank

After you’ve purchased your toilet tank, you’ll need to know how to install it properly. There’s a video below that walks through the process of installing a toilet tank.

If you’d rather read the steps, there’s also a step-by-step guide for how to install a new toilet tank on

Note that the video above doesn’t cover how to properly remove an old toilet tank. However, the article above from does cover that topic.

Are Toilet Seats Universal?

There are two standard sizes of toilet seats in the United States, elongated and round. If you use the same shaped toilet seat, the new seat should be interchangeable with your old seat. However, there are some nonstandard toilet seats. Check out this post for a full explanation: Are Toilet Seats Universal? How to Replace a Standard Seat

What Are the Best Toilet Brands?

The top five most popular toilet brands are Kohler, American Standard, Glacier Bay, AquaSource, and Swiss Madison. For a complete breakdown of each of the most popular brands, check out my other post that has the top fifteen toilet brands: The Top 15 Toilet Brands: Know Who You Can Trust

How Much Do Toilets Weigh?

The average toilet weight is 96 pounds but they can range anywhere from 70-115 pounds. This can be an important factor to consider if you’re buying a new toilet. For more information about toilet weights and what you need to do to replace a toilet, check this out: How Much Does a Toilet Weigh? Summarizing 50 Top Sellers


Leslie has lived in tons of different places that were all in different states of repair. She has experience remodeling and replacing just about everything in a home including the roof. When she's not working on a project, Leslie blogs about home improvement tips to pass on her knowledge to others.

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