How to Fix a Running Toilet

1. Get to know what’s in your toilet. Mechanisms vary, but they all work on the same principles. Flush a couple of times while you watch in the tank with the tank lid off and notice the process.
  • When you push the handle, the chain lifts a flapper, letting a tankful of water fall through the opening in the bottom, into the bowl. As the water level drops, the flapper drops and closes the opening.
  • A plastic float drops as the water drains. The float is connected to a valve that lets water into the tank when the float is down and stops (or should stop) when the float is up.
  • In the middle, there’s also an overflow tube that drains water out into the bowl if it gets too high

2. Catch it in the act. If you’ve waited long enough after flushing and the toilet hasn’t quit running, lift the tank lid and look in.

3. Close the flapper. If the tank is not full and it is not filling, chances are that the flapper is stuck open.
  • Reach in and close it with your hand. If it sticks repeatedly, look for the cause. Make any necessary adjustments.
    • Is the chain catching on something or is the flapper catching on the chain? Try threading the flapper chain through a plastic soda straw to prevent a long chain from getting stuck on things and preventing the flapper from seating properly. Or, replace the chain completely with a loop made from dental floss that is the same length as the chain.
    • Is the flapper wedged open on its hinge?
    • Is the flapper aligned with the opening?
    • If you have a ball seal instead of a flapper, is the wire that lifts the ball straight and does it move freely?
4. Check if the water in the tank is at the water line. Not having enough water in the tank will have the toilet run.
  • If the water is NOT at the water line, check your water valve to see that it is on all the way. If it is NOT, turn it all the way on and your tank should start filling up to the water line (unless the Refill Valve or Float are not adjusted correctly). Try this BEFORE changing flapper or anything else.
5. Try adjusting the valve and float.
  • Pull up on the float with your hand. If this action stops the flow, then adjust the level of the float so the tank stops filling when the water is about an inch (2.5cm) below the top of the overflow tube. If the tank level is too high, the excess pressure can cause water to leak through the flapper into the bowl (even with a brand new flapper).
  • If the float is around the valve post, pinch the metal clip and slide the float down on the wire.
  • If the float is a ball on an arm, try turning the small screws on top of the valve. Sometimes, you can also bend the arm further down.
  • Make sure the float ball isn’t touching anything else. Adjust it so it isn’t dragging against the side of the tank, the overflow tube, or anything else.
  • Depending on the design of the float mechanism and how it relates to the fill tube, the fill tube can occasionally go over the float mechanism and hold it down. Don’t move the fill tube while the toilet is filling; you may be in for a wet surprise.
  • A waterlogged float can cause overflowing (even if the valve itself is functioning properly) so make sure the float ball isn’t leaking or filling with water. If you unscrew the float ball and hear water inside when you shake it, replace the float ball.
  • If the ball valve and assembly are covered in limescale then you could try cleaning (descaling) them (suggest you remove them from the tank 1st). It only takes minutes and is well worth the effort. If you have the ball valve out but cannot get it apart to get at the valve washers its often the limescale that’s gluing it together.
  • If pulling the float up gently to the top of its travel does not stop the toilet running and you’ve tried everything above,you may have to replace the whole refill valve assembly. Replacing the whole valve is a bit more of a project, so check the other possible causes and remedies thoroughly first. If you think you need to replace the valve, it is manageable by one person and not too expensive. Ask for advice at your hardware store, and read the directions carefully that come with the replacement valve.
6. Clean or Replace the flapper and/or flush valve. If the toilet stops filling and then starts again intermittently or water constantly runs into the bowl, you have a slow leak from the tank into the bowl. Place a dye tablet or a few drops of food coloring in the tank. Your local hardware store may have free dye tablets for this purpose. If, after an hour or two without flushing, you see this dye in the bowl, you have a slow leak, a small amount of water running into the bowl.
  • Close the water valve and flush the toilet. If the valve is completely closed, the tank will not refill and you will not hear water running after the tank empties.
  • Pop the old flapper off its hinges, disconnect it from the chain, and pop the new one into place.
  • Don’t forget to open the valve all the way when you’re ready for water again.
  • Try flushing a few times to make sure the chain is the right length for the new flapper. It should open when you push the handle and then drop closed all the way when the tank empties. You may have to trim and adjust the chain by trial and error. Also, make sure that the flapper aligns properly with the opening.
7. Troubleshoot other possible problems. Occasionally, something else will cause water to drain slowly into the tank.
  • The small rubber fill tube leading from the valve to the overflow tube and sometimes the valve itself can act as a siphon. In that case, adjust the valve height or tube height up, or adjust the water level down.
  • The valve itself will not stop the water completely. Some valves can be opened and the rubber seals replaced. If not, you may need to replace the whole valve.
  • One or more of the non-rubber components may break in the toilet’s water valve mechanism, such as the lever connected to the plastic ball that shuts off the water by pressing down on a button as the water level rises. If this happens, the best course of action is to buy a replacement, but super glue can work temporarily in some situations.
  • The water pressure at the small rubber fill tube leading to the overflow tube may be too high, preventing the flapper valve from seating. Turn the shutoff valve at the wall partially closed.
  • The most common cause of slow leaks is a leaky flapper. Over time, this inexpensive rubber part may decay or get old and stiff to the point that it needs replacing, or minerals may build up on it and/or the rim of the flush valve where it seats.
  • If the flapper is still in good shape, sometimes all it takes to make it work is to clean it &/or the rim where it seats.Cleaning may work to remove mineral buildup, but it’s usually best just to replace the whole part. There are a few standard kinds, so take your old one with you to the hardware store for comparison (to ensure you get the right kind). To perform a replacement:
    • Run a finger carefully around the underside of the flapper and the rim where it seats. Remove any uneven buildup of minerals that might cause a leak. Use a sponge with bleach or steel wool or #500 wet-or-dry abrasive paper.

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