How to Fix a Running Toilet
If you have a toilet that either sporadically or constantly runs water, even if you haven't flushed it in a while. This is typically caused by one of the following things:
The rubber flapper at the bottom of the tank is bad - The flapper is what seals and holds the water in the toilet tank and keeps it from flowing into the toilet bowl. If this flapper is not fully sealing the water from the toilet tank will slowly and silently leak into the bowl, which eventually lowers the water level in the tank and triggers the fill valve to turn open and refill the tank. So if your toilet starts running sporadically or seems to be topping itself off every few minutes, that usually means the flapper is slowly leaking and once the tank is low enough, the fill valve turns on to refill it. This can be caused by a dirty flapper which you may be able to clean up to get it to seal properly, or the flapper is damaged and needs to be replaced. This is a pretty easy fix, but not what this video is about.
The toilet fill valve is malfunctioning - This is the usual culprit. The toilet fill valve is the valve that triggers the water to flow into your toilet tank and toilet bowl to refill them when you flush the toilet. This valve has a float trigger that turns off the flow of water to the tank and bowl once the water level in the tank reaches a certain level. The typical failure point is the valve not closing completely. This will cause a slow but constant flow of water into the tank, then the overflow tube into the bowl and eventually down the drain.
Here are the step to replace this valve:
Supplies
New toilet fill valve
Channel locks
1. Remove the toilet tank lid and set it on the floor in a safe location. Turn off water supply to the tank by turning the valve to the right, or clockwise, until closed. Flush toilet to drain the bulk of the water from the tank.
2. Disconnect the water supply line from the base of the fill valve at the bottom of the tank by turning the lock nut counterclockwise. Then remove the lock nut that secures the fill valve to the bottom of the tank and remove the valve from the tank. Both of these lock nuts should be only hand tight, but if they are too tight to remove by hand, you can use the channel locks to loosen them. Remove the existing fill valve from the toilet tank.
3. Lay the old fill valve down next to the new valve assembly. Adjust the top of the new fill valve by twisting the top and bottom of the valve until it is the same height as the old fill valve. Make sure the fine adjustment screw if about half way between the highest and lowest setting on the screw so you will have maximum travel up and down to adjust the float.
4. Install the new fill valve in the tank and attach the lock nut to the bottom of the tank. Hand tighten the nut only - make it as tight as you can. If it isn't tight enough to keep it from leaking, you can use the channel lock to assist, but don't over tighten the nut. Adjust the length of the small rubber refill tube to the size you need in your particular tank, and attach the tube to the valve and clip the other end of the refill line to the overflow tube going to the bowl.
5. Attach the water supply line to the bottom of the valve. Again, hand tighten this nut only, but if you don't have the strength to tighten the nut enough to hold the water, you can use the channel locks to finish tightening the nut. Do not over tighten the nut though. Turn the water valve back on and check for leaks at the bottom of the fill tube.
6. When the toilet tank fills completely, make a final adjustment of the float height as needed with the top adjustment screw, to get the water in the tank to the proper level. Flush the toilet to make a final check. Then replace the tank lid, and enjoy your properly operating toilet.