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How to stop toilet running once full?

Recently my toilet has started running all the time even when it's full. This overflows into the bowl and only stops once the water is turned off.

I'm not sure of the brand of toilet, it doesn't appear to mention it anywhere. The house is about 15 years old though.

How the toilet looks inside. Side note: Can anyone tell me why one side is clean and one side isn't?

How the overall toilet looks

Video of toilet filling from flush

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JacobZ

Hi @Kalliste,

A warm welcome to the Bunnings Workshop community, it is fantastic to have you with us.

It sounds like your toilet's flush valve (outlet valve) isn't sealing properly, allowing water to continuously leak into the bowl. Since the cistern is constantly emptying, it is also constantly filling to counteract this. This is usually caused by a worn-out or misaligned seating washer, which can harden or become damaged over time. If the flush valve itself isn’t sitting correctly or is worn out, it may not be sealing properly, leading to a constant flow of water. Another possibility is debris or limescale buildup preventing a proper seal.

To fix the issue, start by turning off the water and flushing the toilet to empty the cistern. Inspect the seating washer at the base of the outlet valve—if it looks worn or damaged, replacing it with a new seating washer should solve the problem. Clean any debris or limescale buildup around the valve, as even small particles can interfere with the seal. If replacing the washer doesn’t fix the problem, a full outlet valve replacement may be necessary.

As for why one side of the toilet bowl is cleaner than the other, this is usually due to the way water flows into the bowl. The side receiving more direct water flow, which in your case is the side closest to the inlet valve, stays cleaner, while the other side accumulates grime or mineral buildup over time. This is a common occurrence, especially if the water doesn’t circulate evenly around the bowl.

Let me know what you think, and if you have further questions, please don't hesitate to ask.

Jacob

Jason

Hi @Kalliste,

Let me also extend a very warm welcome to the Bunnings Workshop community. We look forward to reading about all your projects and plans for around the house and garden.

I trust you found Jacob's reply helpful.

Just wanted to add that we have a step-by-step guide How to fix a leaking toilet that you can also consult for assistance.

Please let us know how you go.

Jason

Kalliste

Thanks for your speedy response Jacob.

With the seating washer, is there any way I can tell which one I need or are they much the same?

JacobZ

Hi @Kalliste,

Do you know what brand and model of cistern you have?

This is often the best way to work out what seating washer you require. If you can find the brand and model and let me know, I'd be happy to check for you. There is often an identifying tag on the inside of the cistern.

If you don't have any luck, then removing the old washer and bringing it in-store to compare is another way. I'm sure the team at your local store would be happy to help match it up with a suitable replacement.

Let me know how you go.

Jacob

Kalliste

Thanks for the guide Jason.

I'm going to be grabbing the parts this week. I was just wondering in the guide it mentions:

"If water is leaking from the cistern to the pan, it is leaking from the flushing valve. If the leak stops when the cistern tap is turned off, the leak is coming from the inlet valve."

For me, the leak stops when the cistern tap is turned off and the cistern stays full. Does this mean I should actually be replacing the inlet valve seal rather than the seating washer? Or should I just do both?

Thanks!

JacobZ

Hi @Kalliste,

Apologies for that, I missed that key bit of information.

If the water stops when the cistern tap is turned off, then it is likely an issue with the inlet valve.

With that information, it seems like the best place to start is by replacing the inlet valve seal. Step 4 in How to fix a leaking toilet will guide you through the replacement process.

If you find that the leak persists, you can then replace the seating washer.

Let me know how you go.

Jacob

Kalliste

Hi again team,

I am looking into this today and having some issues getting the top off my inlet valve.

Looking on the website the replacement seal is $6 but I can replace the whole thing for $24. Given the reviews are better for the replacement, it seems like the better way to go.

Just wanted to confirm this is compatible with my cistern. It looks to be, but wanted to make sure before buying it:
https://www.bunnings.com.au/fluidmaster-bottom-entry-toilet-inlet-valve_p4926949

Alternatively this, because reviews seem better overall. The design is different, so just want to confirm it'll still work:

https://www.bunnings.com.au/kinetic-bottom-entry-inlet-valve_p4920265

JacobZ

Hi @Kalliste,

As you have a bottom inlet toilet, either of the options you have mentioned will work.

If you run into any issues along the way, please don't hesitate to reach out.

Jacob

Kalliste

Hi @JacobZ

I've made some progress!

A few questions.

This black rubber that was already there is in the way. edit: I thought I could remove, but I'm guessing I'll need to move it so I can screw it back on. One thing is the rubber is pretty brittle. So, if it's something I need how do I go about replacing it?

Also, I've aligned these based on where the height adjuster is, should I be matching the overall height?

As for water level. Everything I've found has said a couple of cm below the overflow. Is that correct?

thanks for your help!

JacobZ

Hi @Kalliste,

Looking at the instructions for the Kinetic Bottom Entry Inlet Valve, there doesn't appear to be a rubber seal on the outside of the cistern. This tells me you should be fine to remove the black rubber and just use what is provided with your new inlet valve.

It's hard to say exactly where the inlet valve should be set based on the old one, but what you have done looks like a good starting point.

You can always adjust the float once it is in place to adjust to what you are seeing. As there will be a watermark inside the cistern, you can adjust based on it to get your level right.

Let us know how you go, and don't hesitate to ask any further questions.

Jacob

Kalliste

Thanks @JacobZ

I removed it and got everything into place but it leaks from the bottom of the bigger white nut.

JacobZ

Hi @Kalliste,

If you replace the black washer and tighten the white nut, does that fix the leak?

Jacob

Kalliste

Hi @JacobZ

Do you mean to put the old one back or to get something new?

If new, what is the best way to determine what I need to get? It looks like this now that it's off.

JacobZ

Hi @Kalliste,

I meant to put the old one back.

As it was not the cause of the original issue, I imagine it will still work.

If not, can you let me know the diameter of the pipe and the rough measurements of the old washer so I can try to find a suitable replacement?

Let me know how you go.

Jacob

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