How do I replace a toilet flush valve?

Try the flapper first. Korky says the flapper "is the most commonly replaced part of the flush valve because the rubber can deteriorate and warp over time," and that this causes a running toilet and water waste. EPA agrees that a worn flapper is a common source of leaks and says it should be replaced at least every five years. Our guides on how to replace a toilet flapper or fill valve and how to pick the right flapper cover that repair.

Replace the whole valve when the valve itself is damaged. Korky says that "over time, your valve can become cracked or damaged, creating a pathway for water to leak," and that when this happens, "it is time to replace your flush valve." In less common cases the flush valve can develop cracks, and Korky says you must replace the valve to repair the toilet. Look for cracks in the valve, and for water that keeps leaking into the bowl even after a new flapper.

Since replacing a flush valve is less common than replacing a flapper, Korky recommends replacing the fill valve and the flush valve at the same time, because you already have the tank open. If your toilet runs and you are not sure which part is at fault, see how to fix a running toilet.

The valve has to match the opening in the bottom of your tank. Korky says toilets have two different size valve openings, a standard 2-inch one and a large 3-inch one. It says that if your toilet was made before the year 2000, you will likely need a 2-inch valve, and that a later toilet might need the 3-inch size. Measure the opening rather than guessing from the age.

Some toilets use a valve made for that model. American Standard, for example, publishes separate replacement steps for its Champion two-piece toilet, its Champion one-piece toilet and its VorMax toilet. If your toilet has a brand-specific valve, use the maker's part, and follow the steps for your model. The steps below are for a standard two-piece toilet with a common tank valve.

These steps combine Korky's instructions with American Standard's steps for a two-piece toilet.

1. 1Get the right parts. You need the valve kit, a tank-to-bowl gasket and matching hardware. Buy them before you drain the tank.
2. 2Shut off the water and empty the tank. Korky says to flush once the water is off and, when the water level settles, mark the level with a pencil. That line helps you check the water level later. Then flush and hold the handle down to drain the rest. Use a sponge to soak up what is left.
3. 3Disconnect the supply line. Put a bucket under the connection to catch the water in the line. Our guide on how to shut off water to a single fixture explains the valve you just closed. If the line is old, this is a good time to swap it.
4. 4Unhook the chain and refill tube. American Standard says to disconnect the trip lever from the chain on the flush valve. Detach the refill tube from the overflow tube.
5. 5Unbolt the tank. Korky says to loosen the tank nuts and bolts with a screwdriver and an adjustable wrench. American Standard says to remove the tank from the bowl. The tank is heavy and made of porcelain, so lift it with care.
6. 6Remove the old valve. Take off the sponge gasket and the mounting nut. American Standard says to use channel locks to unfasten the valve nut from the bottom of the tank.
7. 7Install the new valve. For a 2-inch toilet, Korky says to insert the threaded bottom of the valve through the tank hole with the rubber seal inside, place the chipboard washer over the threads outside the tank, hand tighten the mounting nut and set the sponge gasket over it. For a 3-inch opening, Korky says to measure the hole. If it is smaller than 3 and 7/16 inch, insert the base and hand tighten the nut, with an extra quarter turn. If it is 3 and 7/16 inch or larger, place the black o-ring in the groove under the base first.
8. 8Set the tank back on the bowl. Put the bolts through the rubber washers, then the metal washers, and tighten the nuts. Korky says to have a helper press down on the tank evenly and to alternate sides until the tank is level and stable. American Standard says to fasten the tank nuts until there is china-to-china contact between the tank and the bowl. Korky warns: "Do not over-tighten the nuts, as it can cause the porcelain to crack."
9. 9Set the overflow tube height. Korky says the overflow tube should sit 1/2 inch above the water line and 1 inch below the flush lever nut, and warns that if it is too high, water can leak through the hole in the toilet handle and cause flooding. Korky's valves have a telescoping tube you adjust by loosening a lock nut, so no hacksaw is needed.
10. 10Reattach the refill tube and chain. Clip the refill tube to the overflow tube. If it kinks, trim it. Korky says to leave only one or two chain links of slack.
11. 11Reconnect the water and test. Korky says that once the tank fills, you should turn the supply off again and flush. If the water level is within 1/2 inch of your pencil line, you are done. Check for leaks under the tank, at the bolts and at the supply connection, then flush several times.

Brand-specific steps differ. For the VorMax, American Standard says to turn on the water and make sure the tank fills to 1/4 inch below the top of the overflow tube, then flush 8 to 10 times to prime the bowl. Follow the instructions for your model.

Call a plumber if:

• The tank or bowl is cracked. A new valve will not fix a cracked fixture, and the whole toilet may need replacing.
• A nut is stuck or a bolt will not turn, and you cannot free it without cracking the porcelain.
• The tank leaks at the bolts or the gasket after you have reseated it twice.
• The shut-off valve will not close, or it drips when you disconnect the line.
• You cannot find a valve that fits your model.

HQ Plumbing and Air can replace the flush valve, fill valve and supply line in one visit. We are licensed and insured, we give free estimates, and you get the price up front.