How to Install a Toilet Tank on a Bowl

The toilet tank is the part of the toilet that holds the water, ballcock and flushing mechanism for the toilet. It is attached using two bolts, and is aligned so that the water flows out of the tank into the bowl to flush the toilet. Not all toilet tanks and toilet bowls will fit one another, so make sure you have the right tank to attach to your bowl. Most toilet tanks come with the mechanical parts already installed.

The Tank

  1. Assemble the toilet tank by installing the flush valve in the large hole in the bottom of the tank. If your tank came assembled, then you can skip to Step 4.

  2. Install the fill-valve in the smaller hole on the left side of the tank, and the flush handle on the front.

  3. Make sure the toilet bowl gasket is in place on the bottom of the bowl. Place a rubber washer from the mounting hardware on each bolt, and place them through the bottom of the tank.

  4. Position the tank over the back of the toilet bowl, lining up the bolts with the two small holes in the bowl, and the flush-valve with the large hole.

  5. Attach the washers and nuts to the bolts and tighten with a wrench until the tank is secure.

  6. Attach the water supply line to the fill-valve on the bottom of the tank, and to the water supply line protruding from the wall behind the toilet. Tighten hardware until it stops turning.

  7. Turn on the water supply to the tank.

  8. Check for leaks at both bolts and the fill-valve.

  9. Check the fill-level in the tank and make sure the fill-valve shuts off when the tank is full.

  10. Flush the toilet and check for any leaks around the bottom of the tank.


  • Be careful when adjusting the fill-valve to set the fill-level. If you set it too high, water can leak from the flush handle. Do not overtighten the tank bolts. You can damage the rubber washers and cause premature deterioration and leaks.