How to Replace a Toilet Tank Fill Valve (in Just 9 Steps!)

A toilet whose water continues to run is beyond annoying — it can also indicate a leaking toilet — and might require the replacement of the toilet tank fill valve.

Today, we’re going to learn how to replace a toilet tank fill valve with a modern float cup-style fill valve. Any leaks you have will be long gone. Let’s get started.

What is a Toilet Fill Valve?

A toilet fill valve is a device that controls the water flow that refills the tank and bowl after each flush. Older toilets use ballcocks (plunger-style) for this function.

The toilet fill valve is located inside the tank and can be seen on more modern-style toilets. Most plumbers believe that the fill valve should be replaced every 5 years for the best performance.

how to replace a toilet tank fill valve - illustrated view of fill valve inside tank
A fill valve assembly is a collection of parts that work together to create the largest part inside a toilet tank. They are easy to assemble, disassemble, and install.

How to Replace a Toilet Tank Fill Valve in 9 Steps

Here’s how to replace an old-style plunger-type fill valve with a more modern float-cup fill valve. The process should only take about 1 hour, maybe less.

What You Need to Get Started

  • Float-cup fill valve assembly
  • Sponge
  • Adjustable wrench

PRO TIP: To make sure you’re buying the right part, purchase a universal fill valve kit assembly that fits most toilet models that is high-performance. They are inexpensive ($10-$25) and include everything you need.

Step-by-Step Instructions

  1. Turn off the water supply valve under the toilet tank, flush the toilet, and sponge-dry the tank.
  2. Using an adjustable wrench, remove the top supply slip nut underneath the toilet tank.
  3. Holding the fill valve with one hand, remove the fill valve locknut from under the tank with the adjustable wrench.
  4. Unclip the refill tube from the overflow tube and lift the fill valve straight out.
  5. Purchase a float-cup fill valve at a hardware store or home center. Adjust the height of the new fill valve to fit in the tank by twisting its base. Instructions for this are also on the kit assembly you purchased.
  6. Insert the threaded base of the fill valve through the hole in the bottom of the tank and secure with the locknut.
  7. Clip the refill tube to the overflow tube.
  8. Reconnect the top supply slip nut. Turn on the water supply valve and let the tank fill.
  9. Flush the tank and adjust the float as needed for the correct water level.
You can also watch this video on YouTube. It provides a great overview of how to replace the fill valve.


Here are some great resources related to replacing a toilet flapper. Also included is an in-depth article on how to replace a toilet handle system (which might also fix the problem).

Final Thoughts: How to Replace a Toilet Tank Fill Valve

Knowing how to replace a toilet tank fill valve isn’t hard to learn. Most do-it-yourself homeowners can handle this project in about 60 minutes.

All you need is the most basic understanding of how toilets work, a replacement fill valve kit, and the instructions above.

Call 1-Tom-Plumber

Don’t hesitate to contact us here or call us at 1-Tom-Plumber (1-866-758-6237) if you need help replacing a toilet tank fill valve.

1-Tom-Plumber’s certified team of plumbers and drain technicians respond immediately to any emergency plumbing, drain cleaning, or water damage problem. We also handle the excavation of underground water lines and sewer main lines. Our immediate-response team is available every day and night of the year, even on holidays.

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