How to Replace All the Parts Inside a Toilet Tank

A toilet tank that runs constantly, flushes weakly, or wobbles at the handle usually has more than one worn part inside it. When a tank hits that point, plumbers commonly recommend rebuilding it entirely with a universal repair kit rather than chasing one failure at a time. This guide walks through removing every internal part and installing new ones in the right order, using the kind of full kit sold at most hardware stores.

When a Full Rebuild Makes Sense

Toilets rarely fail all at once. A flapper degrades from chlorine tablets, the fill valve diaphragm stiffens with age, and the flush handle arm loosens from years of use. If your tank is more than eight to ten years old and you are already fixing one part, the other components are close behind. Rebuilding everything in one visit saves you from draining and refilling the tank three separate times over the next year. For a full breakdown of what each component does, see our toilet tank parts list before you start, so you know what you are removing and why.

What a Standard Repair Kit Includes

Most universal kits, including common brands like Fluidmaster and Korky, contain the same core group of parts:

• A fill valve (also called a ballcock) with a refill tube
• A flapper sized to fit a 2 inch flush valve opening
• A flush valve seal or full flush valve assembly for tanks with a leaking base gasket
• A tank to bowl gasket and bolt set if the tank sits separately from the bowl
• A flush handle with trip lever
• A braided supply line

Not every kit includes the flush valve assembly itself, since replacing that piece requires removing the tank from the bowl. Check the packaging before you buy, and confirm the flapper style matches your flush valve seat. If you are unsure which kit fits your toilet, our toilet repair kits guide compares the options by toilet type and tank size.

Tools You Will Need

• Adjustable wrench or channel lock pliers
• A small bucket or towels for residual water
• A sponge to soak up the last inch of tank water
• Plumber's putty or a rubber washer, if not included with the kit

Step 1: Shut Off the Water and Drain the Tank

Turn the shutoff valve behind the toilet clockwise until it stops. Flush the toilet and hold the handle down to drain as much water as possible. Use a sponge to remove what remains in the bottom of the tank, since you will be reaching in past the flush valve opening.

Step 2: Disconnect the Supply Line

Unscrew the supply line nut where it meets the bottom of the fill valve. Have a towel ready, since a small amount of water sits in the line even after draining. Remove the coupling nut that holds the fill valve to the tank from underneath.

Step 3: Remove the Old Fill Valve and Flapper

Lift the old fill valve straight up and out of the tank once the locknut is loose. Unhook the flapper from the two pegs or the ring collar at the base of the overflow tube, then slide it off. If the flush valve seal at the bottom of the tank is also cracked or grooved, this is the point where you would remove the tank from the bowl to replace the full flush valve, since that seal sits on the outside of the tank base against the bowl.

Step 4: Install the New Flush Valve Seal (If Needed)

If your kit includes a full flush valve replacement, drain and disconnect the supply line fully, remove the two tank bolts underneath the tank, and lift the tank off the bowl. Peel off the old spud washer, install the new flush valve assembly through the tank opening, and hand tighten the large locknut underneath before setting the tank back on the bowl with a new tank to bowl gasket. Most rebuilds skip this step because the seal only fails after severe age or a dropped tank lid.

Step 5: Install the New Fill Valve

Set the new fill valve into the tank opening. Most models like Fluidmaster's 400A adjust to the tank height by twisting the shaft, so set it so the top of the valve sits at least one inch above the overflow tube. Thread the locknut on underneath and hand tighten, then give it a quarter turn with pliers. Overtightening cracks the tank, so stop once it feels snug.

Step 6: Attach the Refill Tube

Clip the small refill tube from the top of the fill valve into the overflow tube. Angle it so it points down into the overflow tube opening but does not sit below the tank's water line, which would let water siphon back into the fill valve.

Step 7: Install the New Flapper

Hook the new flapper onto the pegs or collar at the base of the overflow tube. Attach the flapper chain to the flush handle's trip lever with enough slack to leave about a half inch of give when the flapper is closed. Too much slack means the flapper will not lift fully; too little means it will not seal.

Step 8: Replace the Flush Handle

Unscrew the old handle from inside the tank, noting that the mounting nut has reverse threads and loosens by turning clockwise. Insert the new handle, tighten the nut counterclockwise, and reconnect the chain to the flapper.

Step 9: Reconnect the Supply Line and Test

Attach the supply line to the bottom of the fill valve and hand tighten, then add a quarter turn with a wrench. Turn the shutoff valve back on slowly. Watch the tank fill and check every connection point for drips. Adjust the fill valve's water level using the adjustment screw or clip so the water sits about one inch below the top of the overflow tube.

Step 10: Flush and Fine Tune

Flush the toilet several times and watch the full cycle. The flapper should drop and seal fully once the tank empties. If the fill valve keeps running, check that the refill tube is not stuck below the waterline and that the flapper is seated flat over the flush valve opening. A running toilet after a full rebuild almost always traces back to a flapper that is not seating or a fill valve set too high.

Common Mistakes to Avoid

• Overtightening the fill valve locknut, which can crack porcelain
• Leaving too much or too little slack in the flapper chain
• Reusing an old, hardened tank to bowl gasket instead of the new one from the kit
• Skipping the shutoff valve test after reassembly

If you get confused about which part sits where during reassembly, our toilet parts diagram lays out the tank interior piece by piece.

Frequently Asked Questions

Related Guides

• Toilet Tank Parts List
• Toilet Parts Diagram
• Best Toilet Repair Kits