Skip to Content

How to Fix a Toilet Supply Line Leaking [3 Easy Steps]

How to Fix a Toilet Supply Line Leaking [3 Easy Steps]

Repairing a leaking water supply line can be an incredibly frustrating issue, as you probably know.

There are many possible causes for a leaking toilet supply line, and my goal is to help you with this common problem. 

If you’re feeling agitated and like there’s no hope, don’t.

Trust me when I tell you I felt the exact same way at one point, and that’s precisely why I’m writing this article. 

With that being said, hopefully you’ll gain some knowledge on some tried-and-true methods on how to fix your leaking toilet supply line. 

What Makes a Leaking Toilet Supply Line Such a Challenging Problem?

So what actually makes fixing a leaking toilet supply line such a challenging problem to deal with?

There are a variety of factors with the main being troubleshooting the problem.

A question I often get asked is can I use the plumbers’ putty on a leaking toilet supply line? It can be a quick fix and is usually highly effective.

However, be sure that you get to the root of the cause for long term effectiveness. 

Now for a quick insider trick: check your washer fittings. 

The first step is to switch the water off at the shut off valve. Remove the hose from the supply line and of course the toilet tank connection point, and you should now be able to see your washers. 

Finally, remove the washers and replace them. 

Finding the Leak

Now, on to how to actually solve your problem. The absolute first thing that you have to do is to find the leak. You can’t stop the leak if you don’t know where it’s coming from. 

Finding the leak will also be the determining factor in deciding whether you need to replace your toilet supply line or not.

All the information and methods in the world will be useless if your supply line is severely damaged.. 

Have a look where the water is coming from. Is it leaking from the tank itself? Is there maybe a hole in the supply line? 

As I mentioned before, check your washers and their fittings; see if there’s plumbing putty or tape already, which isn’t uncommon. 

Leaking from the Tank

toilet tank water line connection

A common leakage area is from inside the leaking toilet tank itself. If this is the case, you’ll need to disassemble it from above.

You’ll then need to investigate whether the washer on the valve is functioning properly. 

The next step is to have a look at the threaded section and make very sure that there are no cracks or damage in the fill valve body.

If these two aren’t in good shape, the washer must be replaced and reinstalled. 

How to Tighten Water Supply Line Connectors 

If you find that the leak is coming from in or around the vicinity of the fitting itself, this can generally be fixed by simply tightening the fittings. The only tool you’ll need for this is a pipe wrench; the smaller, the better. 

Be cautious when tightening the fitting as damage to it can very easily be incurred.

Note: if your water supply connectors are giving you issues and need to be tightened, the same method can be applied there. 

Leak at Shut Off Valve

If the leak is coming from the shutoff valve, here’s what to do next: close the main water supply to the leaking toilet shutoff valve, and then loosen the bonnet nut on it with an adjustable wrench. 

Use the wrench to tighten the nut again; be very careful to not damage the nut or over tighten it. 

Turn the main water-supply valve back on slowly and wait to see if the leak has been resolved. 

See more details on these steps here, if you run into any trouble.


What if my toilet’s water supply valve is stuck and won’t turn?

Turn off the water supply valve that you’re dealing with.

Then, pour a small amount of oil down the valve’s shaft and allow it to soak for a while. Heat the valve body with a hairdryer and see if your wrench is now effective

What’s the difference between a flexible water supply tube that’s plastic vs braided?

Quite simply, plastic tubes are cheaper but not of the same quality. Braided tubes are more expensive but tend to look more appealing and last longer.

How long do I have until something bursts if it’s leaking now?

It all depends on the severity of the leak. Generally, water in pipes is pressurized so if the leak is spraying out, take action immediately. 


In summary, fixing a toilet supply line leak can be challenging and excessively frustrating,  especially when alarming levels of water are puddling behind your toilet. 

I trust by using some of the tried-and-tested methods mentioned in this article, you can troubleshoot the leak and fix it relatively easily and inexpensively. 

I wish you all the best in your DIY journey!

Sharing is Caring!

Cheryl Epstein

Tuesday 5th of April 2022

My toilet supply line was leaking. I couldn't find where it was leaking. I checked my thread and valve according to your instructions. Later I found out that there was a leak in my valve. Then I followed your shutoff valve instructions & after that, my issue has solved. Thank you for sharing such kind of solution.