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How to Replace a Toilet Water Supply Line (without Tears!)

How to Replace a Toilet Water Supply Line (without Tears!)

The way I see it, your toilet water supply line is either old, it’s leaking, or you’re genuinely interested in understanding how your toilet’s mechanism works.

Whatever the reason, you’re in the right place.

How I can help you:

I battled with this, so I figured that I’d impart my learnings onto others so that they don’t have to struggle as I did.

I’ve always felt quite uncomfortable with this type of work. If I can do it, you can too.


I understand the aversion and general struggle with any DIY situation.

Don’t worry. I’ve worked through this step-by-step and will now be setting you up with a straightforward, how-to guide.

This article will cover:

The steps to change your toilet water supply line and the different types of toilet water supply lines. You’ll also learn lots of helpful snippets of information along the way.

I promise you that by the end of this, you’ll be a whizz at working with plumbing: no pun intended.

Types of Toilet Water Supply Lines

new toilet water supply line

Before I get started, I’m going to give you a summary of the types of toilet water supply lines you might encounter. This way, you can start by identifying what you’re working with.

First, it’s good to know that these supply lines, or hoses, come in three different styles.

The Older “Models”

Supply lines are chrome-plated brass tubes that can be easily identified as they’re incredibly inflexible. They have to be bent into shape and cut the right length to be fitted.

It becomes apparent that:

These supply lines are quite tricky to install, and so if you have to replace yours, it may be a challenge. There’s less room for error.

The main reason you might have to change these supply lines is that brass tends to corrode.

The history of plumbing is quite fascinating. Did you know that toilets were initially only for royalty?

Hold on. I’m deviating—let me get back to where I was.

Modern Hoses

There are two common types of supply lines. They’re both flexible and skip the need for cutting and bending. They’re also easy to install.

The fundamental difference between the two hoses, which are either plastic or stainless steel, is that one is a little cheaper than the other. I’m sure you can gather which it is.

Although a bit more expensive, the stainless steel ones do give you the added bonus of being tougher.

I personally prefer this option because it will last longer. The pricing varies greatly depending on the length and brand.

No matter the case, when yours reaches it’s end-of-life, you’ll get everything from leaks to rusty or mineral deposits that can make your toilet water cloudy…always a cause for concern.

Getting to Work

water supply fitting nut

Let’s see:

Considering that you most likely have either stainless steel or a plastic supply line, I’ll start with how you can go about replacing one of these.

Replacing Modern Types

To install your supply line, you’ll need nothing more than:

  • A new supply line (The most commonly used is 12 inches in length, but measure your current line to be sure.)
  • A wrench
  • A towel (or two)

Step 1: Turning the Water Supply Off

You’ll have to start by turning the water off at your supply valve. My pre-school learning comes into play here: it’s “righty-tighty, lefty-loosey.”

Further, you’ll want to flush the toilet to make sure that the tank is empty. You can now use your towel to soak up the water left in the tank.

This’ll prevent leaks onto the floor upon removal.

Step 2: Removal

how to remove toilet water supply line

Now you’ll need your wrench to loosen the nuts connected to the toilet fill valve and the supply valve.

You might want to use another towel here to deal with water dripping on the floor.

Step 3: Installation

You can do this by maneuvering the new line into the nuts at the toilet fill and supply valve.

You can start by tightening it with your hands. Switch to the wrench if need be.

Step 4: Checks

Start by turning the water back on at the supply valve. You’ll be able to check for leaks.

You may need to tighten the nuts if there’s a leak at one of the connections.

Considerations for Brass Tubes

If on the off chance that you happen to have brass tubes, it’ll be a bit trickier.

This is because you may need to cut and fit it precisely. You can, of course, use your old brass tube to do this.

It may also be that your fittings are just loose, and that’s why there is a leak. In that case, tightening the fittings may fix the issue.

Be careful, though. If you over-tighten it, you may make things worse.

Want to Learn More?

The whole subject of toilet repair and learning how to fix things in my bathroom got me wondering how toilets and other systems work.

I found two different videos settled my curiosity. There’s this video (see below), which summarizes how toilets work pretty well.

I also found another one done by the same YouTuber, which explained home plumbing pretty effectively.


How do I measure the connection size properly if I’m replacing it?

I’ve discovered that toilet supply lines vary in length but are typically 3/8 in diameter.

As for the length, you’ll have to see how long the supply line that you’re replacing is.

When purchasing online, you’ll typically be able to select your desired length, like with this Fluidmaster Stainless Steel Toilet Supply Line.

In-person stores should also allow you the same choice.

Are toilet and faucet supply lines the same? (If so, can they be used interchangeably?)

No, they aren’t and can’t always be used interchangeably. That said, you can buy a universal toilet supply line, like this Fluidmaster Universal Toilet Connector.


Trying to take care of common toilet water tank issues can feel quite daunting.

Hopefully, with the help of this article, it’s been made that much easier.

Of course, as you and I now know, the difficulty depends on whether you have the older or the modern type of supply line. Ideally, it’s the latter.

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