Why is my toilet tank filling up with water?

If you notice that your toilet tank is constantly filling up with water, even after you flush, there are a few common issues that could be causing this.

Water Inlet Valve

The water inlet valve, also known as the fill valve, is responsible for refilling the tank after the toilet is flushed. This valve is connected to the water supply line and allows water to flow into the tank. Over time, this valve can become worn out or develop mineral deposits and fail to shut off completely after the tank is full. This results in the tank continuing to fill and overflow. Replacing the water inlet valve is usually a quick and easy fix.

Symptoms of a Faulty Inlet Valve

• Water continuously flows into the tank and overflows
• Water trickles into the tank and causes it to fill up over time
• Valve does not completely shut off the water after the tank is full

Replacing the Water Inlet Valve

Replacing this valve is a straightforward home repair that can be done in about 15-30 minutes. The steps include:

1. Turn off water supply to the toilet.
2. Flush the toilet to empty the tank.
3. Disconnect supply line from valve.
4. Unscrew mounting nut holding valve in place.
5. Lift out old inlet valve.
6. Install new valve and reattach supply line.
7. Turn water back on and test operation.

Be sure to get an inlet valve that is compatible with your toilet model. Bring the old valve to the hardware store to find the correct replacement.

Flapper

The flapper is the rubber seal at the bottom of the tank that lifts up when you flush the toilet. When you push the flush handle, the flapper opens and allows the water in the tank to rush into the toilet bowl. The flapper then drops back down and seals the bottom of the tank so it can refill. If the flapper is worn out, it may not create a tight seal. This allows water to continuously leak from the tank into the bowl, causing the fill valve to keep flowing to replenish the tank. Replacing a worn flapper is an easy fix.

Symptoms of a Faulty Flapper

• Toilet continues running after flush
• Tank takes longer than normal to refill
• You can hear water running from tank to bowl after flush

Replacing the Flapper

Follow these steps to replace the flapper:

1. Turn off water supply to toilet.
2. Drain tank completely.
3. Remove old flapper and detach chain.
4. Install new flapper and reconnect chain.
5. Turn water back on and test flush.

Make sure to get a flapper that is designed for your toilet model. The new flapper should create a tight seal and stop water from running into the bowl.

Float

The float is connected to the inlet valve and controls its operation. As the tank fills with water, the float rises. Once the float gets high enough, it causes the inlet valve to close and stop the water flow. If the float is set too high or malfunctions, it may not properly shut off the valve when the tank is full. This results in overflow.

Symptoms of a Faulty Fill Valve

• Tank water level is too high after filling
• Float is set too high
• Float does not drop enough to fully close valve
• Float sinks or floats incorrectly

Adjusting the Float

Try adjusting the float if it is set too high:

1. Flush toilet and let tank refill.
2. Note water level – should be 1 inch below overflow tube.
3. If level is too high, adjust float lower on the fill valve rod.
4. Flush again and check level – repeat as needed.

If the float is damaged or not functioning properly, the entire fill valve may need replacement.

Overflow Tube

The overflow tube is the vertical tube inside the tank that the water flows into if the tank level gets too high. If the tube is clogged or obstructed, water cannot flow through it properly. This causes water to overflow down the sides of the tank instead of the overflow tube.

Symptoms of an Overflow Tube Issue

• Water flowing down outside of toilet tank
• Water on bathroom floor around base of toilet
• Gurgling noises coming from overflow tube

Checking the Overflow Tube

1. Flush toilet and listen for proper flow into overflow tube.
2. Inspect tube for obstructions or clogs.
3. Use a coat hanger to gently loosen any debris.
4. Confirm tube is not kinked or damaged.
5. Straighten tube if necessary.

If cleaning the overflow tube does not resolve the issue, the entire fill valve may need to be replaced. This will include a new overflow tube.

Refractory Period

After you flush a toilet, the tank will immediately begin to refill. Once full, you normally have to wait a few minutes before you can flush again. This waiting period is known as the refractory period. If your toilet has a short or non-existent refractory period, the tank will not have enough time to fully refill after each flush. This can result in a continuously underfilled tank that causes flushing issues. The cause is likely a stuck or corroded flush valve that needs replacement.

Symptoms of a Short Refractory Period

• Able to flush toilet again almost immediately after previous flush
• Tank does not appear to fully refill between flushes
• Poor or weak flush force

Lengthening Refractory Period

Replacing the flush valve should restore the proper refractory period. This will allow the tank to fully refill between flushes. Follow these steps:

1. Turn off toilet water supply.
2. Empty tank completely.
3. Detach and remove old flush valve.
4. Install new flush valve.
5. Reconnect flap chain.
6. Turn water back on and test operation.

Be sure to get a flush valve that is rated for your toilet tank size and model. This will ensure optimal performance.

Conclusion

If your toilet tank is filling continuously or overflowing, the most common causes are:

• Faulty water inlet valve allowing water to leak into the tank
• Worn out flapper that doesn’t fully seal
• Malfunctioning tank float
• Clogged or obstructed overflow tube
• Short refractory period between flushes

Replacing the individual components listed above or replacing the entire fill valve assembly should resolve any issues with the tank overfilling. Taking the time to properly diagnose the specific issue will help you fix the problem quickly and restore normal toilet operation. Always turn off the water supply and empty the tank before any repairs.

Issue	Symptoms	Solution
Faulty inlet valve	Water continuously flows into tank and overflows	Replace inlet valve
Worn flapper	Toilet runs after flush, tank refills slowly	Replace flapper
Malfunctioning float	Tank water level too high, float sticks	Adjust or replace float
Clogged overflow tube	Water overflows outside of tank	Clean debris from tube
Short refractory period	Able to flush before tank fully refilled	Replace flush valve

A continuously running toilet tank is an annoyance and wastes a lot of water. Thankfully, repairing the issue is usually a quick and straightforward DIY project. With a few tools and replacement parts, you can have your toilet working properly again in no time.