Why Won’t My Toilet Tank Fill up With Water? Reason and Troubleshooting

Did it ever happen that you just flushed the toilet, and the toilet tank won’t fill up? Well, pretty much everyone has faced this toilet problem at least once. 

Normally, a toilet tank is designed to be filled within 2 minutes. Within 10 seconds, your toilet tank will fill up to ½ inch after you last use flush. 

But if your toilet tank is not filling quickly, there might be some internal issues. We’re here to get you out of this toilet problem. 

First, let’s know why don’t your toilet tank fill up with water. 

Why Does the Toilet Tank Not Fill With Water?

We are gonna unravel all the possible causes of this problem. You can also learn to troubleshoot the problem. 

Toilet shut-off valve

If you are unsure why the toilet’s not filling up, you should check if the toilet shut-off valve is open or closed. The toilet shut-off valve is generally located somewhere behind the toilet. 

A pipeline is connected between this valve and the toilet tank. Toilet water flows through this water supply valve.

So, if the shut-off valve is not opened properly, your tank won’t fill up with toilet water. You can just open it properly and if it’s clogged, try removing the clog. You can take help from plumbers as well.

Faulty fill valve or misalignment 

Toilets filling problems come from the toilet tank fill valve. It’s responsible for filling up the toilet tank after each flush. A toilet fill valve remains connected with the water supply line and the floating ball or cup. 

When you use flush, the floating ball or cup comes down to the bottom of the tank and empties all remaining water. The fill tube or valve starts its work. First, it starts to fill up the water through the water supply line. As a result, the floating ball or cup starts to gain height, and after a particular height, it signals the fill tube not to supply more water.

Any defects or misalignment of a fill valve can stop the process of filling water. So, if the toilet is not filling up, it may be the result of the toilet fill valve not working properly. Try to readjust it or if you see any fault, replace it.

Debris in the water valve or tank

Another most common problem is debris inside the pipeline or tank. It’s common that your toilet tank or water valve can get stuck by some debris. The debris inside the water valve or tank slows down the refilling process.

You can just clean the debris in this situation to solve this problem. But if the problem remains the same after cleaning the clogged pipeline or tank, you should check for other possibilities too.

See Related: how to fix a slow filling toilet tank

Low water pressure

Another important reason could be low water pressure. Low water pressure is the result of various circumstances. Low water flow, clogged pipelines, debris in the pipeline, and leaking pipelines are the most obvious reasons behind this problem.

If you are using a toilet for several months, ending up with clogged pipelines or debris inside the pipelines is normal. You can just simply remove the pipeline and clean it properly. Moreover, if you see a leaking pipeline, just replace it, and it will solve the low water flow problem.

Defective overflow tube

The toilet tank overflow tube is a vital part of a toilet tank. The work of this overflow tube is simple. It drains the excess amount of water into the toilet bowl to get rid of the overflow.  It’s situated in the middle of the tank.

Now there can be circumstances where the overflow tube can get cracked. If this happens, the water will start to flow into your toilet bowl continuously. To get rid of this, you should replace the overflow tube. It’s an easy process; just remove the old valve carefully and replace it with the newer one. You should be cautious about choosing the right-sized overflow tube, though.  

Float ball or arm misalignment

There’s a float tank ball or float tank cup in pretty much every toilet tank. It is generally connected with a float arm. This arm is adjustable. The floating tank ball, cup, and arm keep connected with a fill valve. 

The arm and float ball or cup jointly help the opening and closing of the filling valve. Now, if the alignment of these parts is kept too low, then the tank water will be so little.

On the contrary, if the float ball or cup is set too much higher, it will let the tank overflow and eventually stop working. Again, any defects in the ball, cup, or arm will stop the regular work of a toilet tank.

You can just manually adjust the float ball, cup, or arm if it seems insufficient to you. Furthermore, if you see any defects in those parts, simply replacing these will get you out of this problem.

Defective flapper valve

A toilet flapper valve is a piece of rubber object which is located at the bottom of a toilet tank. This piece of rubber seal allows the toilet water to flow into the toilet bowl when you use the flush. 

Again it comes down to its own place when the toilet tank starts filling up. It then holds the water till the next flash.

The toilet flapper valve is generally connected with a small chain. If this chain gets stuck somehow, the rubber seal will not sit properly into the hole, and this can cause a water leak continuously. Furthermore, the iron flapper valve is highly corrosive and will rust within months.

So, you should check at least 3 or 4 times a year and clean it properly to get rid of this. And if you see any defect in the chain or rubber seal, you need to replace them with a new one.

Damaged bowl

Damaged toilet bowls can also create this problem. Toilet bowls damages are harder to find. A cracked bowl tends to leak water slowly. You can’t find out where the water is leaking since it’s a defect inside the toilet bowl. You can only find some water on your floor.

In this situation, you cannot solve this problem on your own. Maybe contacting your plumbing service would be the best solution.

See Related: how to fix crack toilet tank


So, you learned about why your water tank is not filling up. Of course, you can solve each of these problems on your own. 

But if it seems critical and you can’t find anything similar to these, then you should contact a professional.


How long should it take to fill a toilet tank?

A toilet tank should fill up within 2 or 3 minutes. But if your toilet takes longer than usual, you should check for problems.

Can I manually fill the toilet tank?

Yes, you can manually fill the toilet tank with a bucket of water. Fill your tank with the expected limit, and it will work perfectly. It’s very much unusual, though.

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