How do I change a bottom entry fill valve in my toilet cistern?

Fill Valve

Welcome to this guide to replacing the bottom entry fill valve in your toilet cistern. Below you will find step-by-step instructions, a video guide and a list of toilet manufacturers that this fully adjustable fill valve from FlushKING will fit.

Tools You’ll Need

You will find that FlushKING products are simple to fit without tools, however you will need to have tools ready to remove the old valve from the toilet. You will need:

  • Pair of grips
  • Flat head screwdriver
  • Towel

What product do you need?

You can check what product you need by looking at your existing cistern and identifying where the water supply is.

Side Entry Fill valve

If your toilet cistern has a water supply on either side as highlighted, you will need the Side Entry Fill Valve.

Bottom Entry Fill valve

If your toilet has a water supply connecting at the bottom of the cistern, you will need a Bottom Entry Fill valve.

Bottom Entry Fill Valve

Whilst isolating the water supply to the toilet cistern, it is usually a good idea to consider changing the flush valve as well.

Video Guide

If the toilet in these instructions or video does not look exactly like your toilet cistern, don't worry! The mechanics inside are all very similar.


Step-By-Step Guide

Bottom Entry Fill Valve

1. Check that you order the correct fill valve for your cistern type - when you have removed the cistern lid look inside. Does your water connection pipe enter it at the bottom of the cistern? Left or right makes no difference, it will either be from the bottom or the side. Use the comparison above to compare to your toilet cistern. For this how-to guide we will use the Brass shanked, fully adjustable height, bottom fill valve as it's the most universal and robust fill valve.

Bottom Entry Fill Valve

2. When you look inside a bottom entry cistern you will see a fill pipe coming up from the bottom of the cistern with a float of some type either at the end of an arm or built around the pipe itself. If this is not the case, and your water pipe connects at the side of the cistern the principle is the same, but you need a side entry fill valve instead, and follow the instruction guide you will find here.

Bottom Entry Fill Valve

3. Ok, now we are sure we are working on a bottom entry cistern, the first thing you need to do is to switch of the water on the isolating valve on the water connection (if your toilet hasn't got its own isolating valve you may need to locate your stopcock and turn off your water supply). You will need your flat head screwdriver and use it to turn the screw head on the isolator 90 degrees to the off position.

Bottom Entry Fill Valve

4. Flush the toilet repeatedly to drain out any water in the cistern, and ensure the water is fully off by checking the cistern isn't filling again. You will need to use your towel to dry out any remaining water so that it is completely dry otherwise when you remove the old fill valve this water will escape as it is the lowest part of the cistern. Just soak it up and ring it down the toilet bowl, then place your towel under the cistern to catch any trapped water.

Bottom Entry Fill Valve

5. Now you are ready to disconnect the water supply from the fill valve underneath the cistern. Take your grips (or an adjustable spanner) to the nut on the isolating valve or tap connector that is screwed onto the bottom of your fill valve and turn it anti-clockwise till it loosens enough to undo the rest by hand. You will get a small amount of water that is trapped in the pipe leak out, so make sure your towel is below to catch this.

Bottom Entry Fill Valve

6. You are now ready to remove the old fill valve as it is only held into the cistern with a plastic back-nut (normally plastic to prevent the cistern getting damaged). You should be able to undo the back-nut by hand as it only needs to be hand tight, but if it is being stubborn due to old sealants, use your grips to loosen it. Remove the nut completely and discard as your new unit will have its own back-nut in the box.

Bottom Entry Fill Valve

7. The fill valve should now lift out without any resistance at all, and make sure you remove any old rubber washers from inside the cistern that may be perished and stuck around the hole you now have in the bottom of your cistern. Take a bit of time now to clean around the hole inside the cistern and also underneath it, as you will be need it to be smooth and clean to get a good watertight seal when the new FlushKING unit goes in.

Bottom Entry Fill Valve

8. Take out your new FlushKING adjustable fill valve and offer it up to the cistern so you can adjust the height to fit your toilet cistern. To adjust the height, push up the grey clamp ring just above the threaded part of the stem to unlock the adjustment thread, then pull the lower section down until it is at the correct height for your cistern. Once you are happy with the height, pull the locking ring back down to lock it in place. (Don't worry if it's not quite right, this can be done after it is installed.)

Bottom Entry Fill Valve

9. Remove the back-nut from the new fill valve, making sure to leave the coned rubber washer in place as this will create the watertight seal at the bottom. Lower the new FlushKING valve into the cistern making sure that as you lower it the green float that is wrapped around the pipe is free to move up and down as this is the only moving part that needs clearance. Once you have the threaded end through the hole, check and adjust the height of the pipe again to fit under the closed lid.

Bottom Entry Fill Valve

10. Take your back-nut from the FlushKING fill valve and you will notice that it has tabs on it to make it easier to tighten by hand. You shouldn't need to use grips here as the design of the cone washer and the back-nut should create a watertight seal simply by hand tightening. So place the nut over the threaded brass shank and turn clockwise until the slack is taken up, check the cone washer is sitting central in the hole and then nip the back-nut up until it feels tight and offers resistance.

Bottom Entry Fill Valve

11. Now it is time to connect your water supply back to the cistern by reconnecting the nut from the isolating valve or tap connector (although this is the perfect time to add an isolating valve whilst the water is off). Switch on the water and check for any leaks by running your fingers over every joint you have worked on. Once you are happy all is dry and there are no leaks, test the fill valve by flushing the toilet and allowing it to refill.

Bottom Entry Fill Valve

12. At the top of your new FlushKING fill valve you will see a grey arm with a green dial on top of it. This dial is how you adjust the rise and fall of the float to set the water fill level. Keep adjusting this up or down until the water settles at a level just below your overflow pipe, which may be a plastic pipe exiting your cistern to a waste pipe away from the toilet or a modern internal overflow flush valve as pictured here with the FlushKING flex-mount flush unit. Once you are happy with the level, check underneath for any leaks. Now replace the cistern lid and you're done!

Compatible with

Compatible brands

Browse our range of fill valves here

Did you know?

The Environment Agency has developed a methodology for identifying and classifying relative levels of water stress in water company areas in England. The Government has used this map to designate areas of serious water stress for the purpose of accelerating water metering.