Why Is My Toilet Tank Not Filling?

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The toilet is probably one of the most important items in most people’s houses but probably one of the least talked about and considered. But when you suddenly can’t flush because the toilet tank is not filling with enough water or at all…

Most of the plumbing issues we tackle here at In-House Plumbing Company are not the DIY type of repairs as we handle a lot of underslab sewer and water pipe repairs.

Luckily for you, the toilet is typically pretty straightforward in its design and in troubleshooting problems without calling a plumber.

With toilet problems as with most problems, it’s often about narrowing down the possibilities until you find the culprit.

So if you’ve been asking yourself, “Why does my toilet tank take so long to refill?” Or why it isn’t filling at all, here are some of the most common reasons that you can check for on your own.

Check the Water Supply and the Water Supply Line

Let’s start with something really simple, the water supply and the water supply line.

Make sure the water supply shut off valve is turned on. Sounds too simple but sometimes it really is just that easy.

If the valve is turned on, check for leaks along the supply line. Check the line itself and at the valves where the line connects to the toilet tank and to the cold fresh water line either at the floor or in the wall.

With a toilet supply line leak, the tank still fills up just slower and slower until you get it fixed.

Now if you’re in an older home with older pipes and fixtures, you could have a clog in the supply line.
Turn off the water at the shut off valve and use a wrench to remove the line at the tank.

Position the end that was attached to the tank into a bucket, and turn on the water. If there isn’t any water coming out or it’s coming out at a trickle, then there is something potentially wrong with the supply line, the shut off valve, or the cold water line feeding into the toilet supply line.

If you replace the supply line and/or the shut off valve, and you’re still having trouble with your toilet tank not filling, you might have a blockage or leak somewhere in your fresh water pipes.

If that’s the case, we can always come out and check for a blockage or do a leak test and help you if any repairs are necessary.

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Check the Float

A common problem with a tank that isn’t filling up is the float. If it is too low, it stops the flow of water coming into the tank leaving you with an empty tank or one with not enough water.

Check this by taking off the tank cover. For older toilets, look for a float ball attached to a float arm. Newer toilets often have a cylinder float.

For a float ball, look for screws or dials that you can adjust to raise the arm and the ball. Some people also gently bend the arm to adjust the float ball. For a cylinder float, squeeze the clip to release and move the float to the desired height.

Repair or Replace the Fill Valve

The fill valve is attached to the float. When you flush the toilet, the float sinks to the bottom of the tank opening the fill valve. Water rushes out and up the supply line through the open fill valve into the tank.

As water fills the tank, the float rises until it’s full.

If something is wrong with the fill valve then guess what? You got it, there will be little to no water in the tank.

You want to check for a few things if you think it’s the fill valve. One, old and worn out washers. Two, debris in the fill valve causing a blockage. Or three, a broken fill valve.

For scenarios one and two, either replace the washers or flush out the blockage. And with scenario three, you should replace the fill valve.


Trip Assembly

The trip assembly is part of the handle on the inside of the tank. If this is broken or bent, the tank might not fill when you flush the toilet.

Sometimes you can use a paperclip in a pinch if the chain is broken. But it’s not a permanent solution. In either case, go ahead and get a new trip assembly at the hardware store and replace it.

Be sure to take the old trip assembly to the store with you so you get the right replacement part.


If the flapper isn’t sealing correctly against the flush valve hole, water from the tank will continually run into the toilet bowl.

Make sure the flapper or the chain attached to it isn’t caught on something preventing it from going down all the way.

Older toilets could also have a buildup of debris causing the flapper from sealing. Cleaning it off will solve this problem.

But if none of these problems exist, it might time to replace the flapper all together. Just like with the trip assembly, remove the old flapper and take it with you to the store when you go to buy a replacement.


In-House Plumbing Company

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