The Comprehensive Guide to Gutting Out a Toilet System

April 11, 2016


toilet tank replacement


In this post, we discuss how to replace the internal components of your toilet system. The toilet system is the 'business end' of your toilet as illustrated in the picture above. If your toilet is malfunctioning, the problem is likely due to problems in your toilet system. A running or leaking toilet could cost you a fortune in wasted water and associated damage.

And let's not forget the expense of calling out a plumber. Fortunately, in this post, we outline how you can replace the internal components of your toilet system with only a screwdriver and a wrench.

Skip that plumber's hefty bill and fix the problem yourself even if you don't have any plumbing experience.

Learning objectives

In this guide we've going to show you how to:

  • Dismantle the toilet system
  • Replace all of the parts
  • Put the system back together
  • Check it for leaks

Common toilet faults

The most common toilet fault is when the toilet constantly runs or runs intermittently.

When a toilet constantly runs, the problem is typically due to a faulty fill valve. Specifically, the fill valve isn't completely closing.

If your toilet intermittently runs, the issue is likely due to the flush valve.  Here, the flush valve opens slightly for a few minutes and then closes gain.

The toilet system

The toilet system typically sits at the back of the toilet bowl.

And it's here you're most likely to experience problems.

This is because the toilet system houses the vast majority of a toilet's inner workings.

The inner workings of a toilet system

The toilet system stores water needed to flush away human waste.

Like a car engine, multiple issues can go wrong with a toilet system.

Within every toilet system resides two main components.

These components consist of the following valves:

  1. Fill valve (Ballcock) - this sits within the system and allows the system to fill with water, and then closes the water flow and allows the toilet to refill. The fill valve also sends water to the toilet bowl via the overflow tube. This is also joined to a float cup or float ball system.
  2. Flush valve: this allows water to be released into the toilet bowl. This is attached to the flapper and handle. The flapper is raised when you flush the toilet, allowing water to escape into the toilet bowl.

When your toilet runs constantly or intermittently, you can be sure one of these two valves is at fault.




Is there a problem with the flush valve or fill value?

To determine which valve is causing your toilet to run, you must look within your toilet system.

Specifically, you must investigate your overflow tube (see image above).

When water is spilling over the top and into the overflow tube, you can be sure the problem is because of a faulty fill valve. It's easier to replace the fill value rather than trying to repair it.  You can pick one up at your local hardware store for around £15.

Rule out water level issues before you replace parts

The water may be set too high so the toilet never knows when it's full and never knows when to shut off. Adjust the water level with reference to the type of fill valve you have. So try to adjust the water level before you replace the fill valve.

Rule out a faulty flapper

If water is below the top of the overflow tube, this generally signifies the flush valve is leaking. This leak allows water to trickle into the toilet bowl. This prevents the fill valve from closing, so the toilet is constantly running (put some coloured water into the system and see if it drains into the toilet bowl even though the toilet hasn't been flushed). This may be corrected by purchasing a replacement flapper (see image above). If the flapper is bad, water is constantly leaking into the bowl and so the fill valve never stops trying to fill the toilet.

Alternatively, the problem may reside with the chain that connects the flapper to the handle (see image above). If there is no slack in the chain, the chain may be holding the flapper up allowing water to escape.

If all seems ok, hold down the flapper with your hand. If the toilet stops running, you know the flapper must be replaced. Remove the old flapper and take it to your local hardware store for a like-for-like replacement.




Buy required parts

Now we assume you've taken the above steps and the problem still hasn't resolved itself.

We will thus show you how to replace the insides of your toilet system.

We urge you to replace the following parts:

  • Fill valve
  • Flush valve
  • System gasket
  • System bolt kit
  • New handle

We outline in three easy steps how you can replace the inner workings of your toilet system in less than an hour with little more than a wrench and screwdriver.


remove toilet tank


Step 1: Remove the toilet system

It's much easier to replace faulty toilet system parts when the system is disconnected from the rest of the toilet unit. We shall thus explain how you can remove the system from the rest of the toilet.

Before you start, clean everything.

Remember, you're working around a toilet!

So let's clean it.

Once you've cleaned the toilet, put some towels down and turn the water mains off.

And flush the toilet to remove water from the system.


remove water supply line


Once all water has drained, it's time the remove the water supply line from the system. You may require a wrench to loosen the supply line.


remove wing nuts


Remove the wing nuts from the system bolts located at the bottom of the system that attach the toilet system to the toilet body. Again, you may need a wrench to complete this step.

The system should now be detached from the rest of the toilet.

Tip all remaining water from the toilet system into the toilet bowl.

Now the toilet system is disconnected, remove the old parts by following step 2 below.

Step 2: Remove inner parts from the toilet system


remove fill valve


You will need to remove the fill valve. You may need a wrench to remove the screwed on bolts at the bottom/outside of the toilet. Once the bolt is removed, the fill valve from within the system will slot out.

Also, from within the system, remove the flush valve and throw it away (we remove the flush valve assembly below).


remove bolts


Remove the system bolts at the bottom of the toilet system. These will be very stiff, so use a wrench.


remove gasket


Once off, remove the ageing system gasket and throw it away.


remove flush valve


Remove the flush valve assembly that's was attached by the system bolts/system gasket you've just removed from within the system. An oil filter wrench or jar opener should do the trick.

Lastly, remove the toilet handle and throw it away.


empty toilet tank


Now you have completely gutted out the toilet ready for the replacement parts to be added.

Step 3: Reassemble the toilet with new parts


insert tank bolts


First off, insert new system bolts. Bolts should come with a washer and gasket. Bolts are inserted into the system at the internal rear and attached the toilet system to the rest of the toilet.


insert flush valve


Now, install the new flush valve assembly . - this goes inside the system and marries up to the rest of the toilet unit.


insert flush valve 2


The flush valve assembly is sealed using a large rubber system gasket (see image below).



Install the new fill valve assembly (see image below). This should include a gasket and plastic screw.


fill valve assembly


Now install plumber's tape around inlet thread around the fill valve thread (see image above). This prevents leakage.


install new gasket, washer and nuts on tank bolts


Install the washer and nuts on the system bolts (you will need a wrench for this, but do not over tighten).


Put toilet tank back on body of toilet


And put the system back on the toilet base. Install the system to the base nuts (using gasket-washer-nuts).

Install the flush handle.

Now it's time to reattach the supply line.

Adjust the top of the fill tube to above the fill line (there's a fill line mark inside the system). Please read the manufacturer's instructions.


flap - have some slack on line


Attach the chain between the flapper and the handle. The chain needs just a little slack.

Adjust the water mark of the fill valve to the system mark (read the manufacturer's instructions for this).


attach fill tube


Attach the fill hose (making sure it is clipped in securely or you'll have water squirting everywhere).

Now turn the water back on.

Flush the toilet to see if it works correctly. Look inside the system whilst this happens.

Attach the chain to the leak preventer (with reference to the manufacturer's instructions).

Check for leaks and put the top back on the toilet.

That's it for now

We hope you enjoyed our post on replacing the internal workings of a toilet system. Chech back soon for more articles on related subjects. And don't forget to share this post on social media channels!


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