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How To Change a Toilet Tank

A toilet is composed of a bowl and a separate tank, in most instances. The toilet tank contains the ballcock, the flush valve, and the flush handle. The ballcock controls the entrance of water into the tank and the resulting water level. The flush valve includes the overflow tube and the flapper. It controls the discharge of the stored water supply into the toilet bowl. The flush handle operates the flapper. You can repair all these components or replace them, as needed. Occasionally, it becomes necessary to remove the entire tank because it has cracked or because the tank mount bolts have started leaking. Follow these simple steps to remove and replace the toilet tank.


Replacing a toilet tank is rarely needed but easily done

Replacing a toilet tank is rarely needed but easily done

  1. Turn off the toilet water supply at the wall. If the valve is corroded, feels rough in operation, or sticks, turn off the water at the house main shut off valve.
  2. Have a shop vacuum, rags, or a sponge handy.

Tank removal

  1. Flush the toilet and hold the flush handle down until almost all the water runs out of the tank and into the bowl.
  2. Use the shop vac, rags, or a sponge to remove the remaining water in the tank.
  3. Disconnect the water supply tube at the bottom of the tank.
  4. Use a screwdriver to hold the tank mount bolts inside the tank.
  5. With a socket and ratchet or an open-end wrench, remove the tank-to-bowl nuts under the back edge of the toilet bowl and beneath the tank. Some tanks are mounted to the bowl with 2 bolts and some use 3 or 4.
  6. Rock the tank gently and lift it straight up until it clears the bowl. Lay the tank down on its side.

Tank installation

  1. Place the large flush valve gasket over the flush valve nut on the bottom of the tank. Make sure that the flush valve nut is tight first.
  2. Verify that the ballcock nut on the bottom of the tank is also tight.
  3. Slide a mount bolt gasket on each mount bolt and up against the bolt head.
  4. Place the tank on the toilet bowl. Verify that the flush valve gasket is sitting squarely in its recess in the toilet bowl.
  5. Install a mount bolt in each hole in the bottom of the tank.
  6. From underneath the toilet bowl, install a gasket, washer, and nut in that order.
  7. Tighten each nut gradually until the tank bottom touches the top of the toilet bowl or the tank is snug and resists movement.
  8. Connect the water supply tube.
  9. Verify that the ballcock fill tube is correctly installed in the top of the flush valve overflow tube.
  10. Turn on the water supply and allow the tank to fill.
  11. Inspect the bottom of the tank and make sure there are no leaks.


If necessary, adjust the fill level with the ballcock adjustment screws.

Do not ever bend the float rod to adjust the water level in the tank.

The ballcock mount stem and nut are plastic in almost all cases. Do not over tighten the ballcock mount nut.

If the mount bolts are too badly corroded to remove, simply slide a hacksaw blade between the toilet bowl and the bottom of the tank and cut the mount bolts in two.

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