No one likes dealing with broken toilets, but one of the more frustrating and common issues is when toilets stop filling with water. Many homeowners spend lots of money calling out plumbers when actually the issue is cheap and easy to fix.

If your toilet is not filling with water, the most common causes relate to the water supply or the toilet fill valve. A water supply line can become clogged and might need replacing. A fill valve may simply need adjusting or potentially replacing, which costs around $20 and takes 30 minutes to do.

When you activate the flush, the toilet tank’s water is released through the flush valve. There are several reasons that the mechanism can fail. But first, let’s look at how to determine and address the problem.

troubleshooting: why your toilet isn’t filling up with water

The reason why toilets sometimes stop filling up with water is usually either related to the water supply itself or the fill valve. The fill valve is part of your toilet responsible for refilling the tank after it’s been flushed. 

If your toilet is not filling up with enough water, you can simply adjust the fill valve. Whereas if you have a faulty fill valve, you might find that your toilet is slow to fill up and it produces a hissing sound. Sometimes the fill valve simply needs adjusting whereas on other occasions you’ll need to replace it. 

Within this section, I’ll take you through the steps to adjust your fill valve, test to see where the issue is located, and how to replace your fill valve if necessary (don’t worry, it’s easy). 

how to fix a toilet bowl that isn’t filling up with enough water 

Most of this guide is geared toward homeowners whose toilet isn’t filling up with water or is filling too slowly. However, I’ve noticed that many toilets don’t fill up with enough water and homeowners don’t know how simple this fix is.  

It’s easy to adjust how much water enters your toilet bowl. You can simply adjust the float by using a screwdriver, as shown in the diagram below. Twist the screw to the right to raise the float arm which allows the toilet to continue filling for longer. You should hear a clicking noise each time the arm raises. 

Once you’ve twisted the screw right, the water level in the bowl should increase. There might be some trial and error but keep adjusting the screw until the level is correct.

However, if this hasn’t fixed the overall problem, move on to my next fixes. 

discovering the root cause of a toilet not filling with water 

The first thing you should do is test your toilet fittings to figure out the cause of your toilet bowl not filling up with water. I’ll help you figure out if the issue relates to the water supply, the braided hose supply line, or the toilet itself. 

Firstly, test other taps within the bathroom to confirm that the water supply to your house is functioning as it should. 

1. Shut off the water valve by your toilet. It’s normally located to the rear left of the toilet. Turn it clockwise to shut the valve. 

Note: keep twisting the valve right until you can’t twist any more – often these valves are stiff and may not have been moved in years. If it won’t move, another option is to shut off the water to your entire unit or house. 

2. Flush your toilet and hold the handle down to remove as much water from the tank as possible. 

3. Use a sponge to remove any excess water from the tank and squeeze it into a bucket or a drain. 

4. Twist off the braided supply hose from the toilet tank (turn left to loosen) and remove the braided hose. 

5. Once the hose is removed, hold the hose over the bucket and slowly twist it back on the water supply. If water shoots out from the braided hose, you’ve confirmed that the issue relates to the toilet itself. 

If however water does not come from the braided hose, you’ll need to replace the hose, and here’s a video showing you how to do that: 

Once you’ve determined the cause of the toilet not refilling is not related to the water supply line, move on to my next step where I cover the fill valve.

the fill valve fix: how to solve your toilets water supply problem

A faulty fill valve is the most common reason a toilet may not fill up with water. The fill valve regulates water flow into the toilet tank after flushing. 

If the fill valve is damaged or worn out, it may not allow enough water to enter the tank, resulting in a low water level. Over time, sediment, debris, or mineral buildup can accumulate in the fill valve, obstructing the water flow. You may also hear a hissing noise and see water leaking from the top of the valve. 

The best way to test if you have a faulty fill valve is to remove the toilet lid and tap on the fill valve. If it fills, you know the fill valve is to blame. 

The first thing you should do is check to see if your fill valve float is rubbing against the side of the tank at all. The float needs to be unobstructed to work correctly (and tell your toilet tank to fill up with water) and sometimes it can twist and rub against the tank. 

Once untwisted, try flushing the toilet again to see if it refills correctly. If not, you’ll need to replace your fill valve.

Some people will recommend cleaning a fill valve rather than replacing it, but fill valves (on Amazon) are actually very cheap (on Amazon) and easy to replace. It should take less than 30 minutes and here are easy-to-follow instructions: 

disconnect the water supply from your toilet.

Disconnect the water supply first by turning off the shut-off valve. Turn the valve clockwise until it won’t turn any further.  

If the valve can’t be turned then you can always shut off your main water supply. Normally this is located in the basement, by your water meter, or wherever the local supply enters your home.

Then drain off any remaining water from the tank by holding the flush button, and then mop up using a sponge inside the toilet tank. The more water you’re able to mop up here, the less messy the next step is going to be.

Remove the old fill valve

The next step involves removing the existing toilet fill valve from your system. First, you’ll need to remove the nut at the bottom of the toilet as shown in the picture below:

You should be able to loosen this nut with your hand strength but if not you can use adjustable pliers like these (on Amazon).

Then carefully and slowly lift the valve from the tank. Once you’ve removed the hose, the fill valve should just lift right out.

fit new fill valve

Once you’ve removed the old fill valve, make sure you clean the area of the toilet where the old fill valve was located. This will ensure a tight fit with your new unit. Then follow these instructions:

1. Position the valve shank onto the fill valve.
2. Attach the remaining refill tube (a rubber tube that goes from the fill valve to the overflow tube of the flush valve) to your new fill valve.
3. Insert the fill valve base into the opening of the tank.
4. Press down on the valve shank and use a wrench or pliers to securely re-attach the locknut (beneath the toilet that you removed earlier), ensuring that the valve is sealed.
5. Reconnect the water supply line to re-establish the water flow.
6. The marking on top of the valve should be at least 1 inch above the overflow tube. To adjust your new fill valve, follow the manufacturer’s instructions included in your new purchase (but this is likely to be the same instructions I mentioned earlier relating to the screw on top of the fill valve).

I also found this video on how to replace a toilet fill valve that you may find useful: