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A How-To Guide on Overflow Pipe Leaking: Ways to Fix It

It is not unusual for things to break around your home. Appliances can stop working, or pipes can start leaking and overflowing at any time. Once in a while, you find the water coming out of the overflow pipe. There is always a reason behind the leak, which is essential to identify a solution. This article guides how you can identify leaks and ways to fix an overflow pipe leaking.

Identify the Leak

The first thing you ought to do to fix an overflow pipe leaking is to find out where the leak is. You need to work out which tank or cistern is overflowing. If the overflow pipe is at the ground level, it is probably a toilet cistern that’s leaking.

However, if you find the water coming out of the overflow pipe at loft level or comes out from the eaves of the roof, the source could be your central heating tank or cold water storage cistern. Check the water level to ensure that you have located the leak. If the water is near the overflow point or is higher than the usual level, then that’s where the leak is coming.

Shut Off Water Supply & Drain the Water

If you have identified the source of overflow pipe leaking, you need to stop the flow of water and drain it to fix it. Use an isolation valve to turn off the water in a toilet cistern. For water tanks, turn off the main waters at the stopcock. Then, turn on the bathroom taps to drain the tank.

Overflow Pipe from Toilet

It is easy to detect overflow pipes in the toilet; they would be running outside and located right behind the toilet. These pipes could be made of copper, metal, or plastic. Toilet overflow pipe happens because the water flow at the cistern isn’t stopping. You need to fix the float valve as it could be set too high – try lowering its position. Next, you can also check the water pressure to fix an overflow pipe leaking. If the water pressure is high, lower it by an isolation valve.

Overflow Pipe from Central Heating Tank

The central heating tank is present in the loft of your house. This tank supplies water to the heating system. If there is water coming out of the overflow pipe, it could be because the water feed isn’t stopping due to a faulty valve. It could also be because of any problems with the hot water cylinder. In either case, you will have to replace them to fix them.

Overflow Pipe from Boiler

Combination boilers have a pressure relief valve that releases water when its pressure is high. The pipe is made of copper and leads to the outside. So, the boiler overflow pipe leaking occurs when the pressure inside the boiler increases. It may also happen when the pressure relief valve isn’t set correctly. Lastly, it could be because the boiler is old and has leaks from other parts. So, it is better to call an expert to fix an overflow pipe leaking from boilers to ensure safety.

Overflow Pipe from Copper Cylinder

The overflow from the copper cylinder pipe runs into the cold water feed. This pipe allows the water to expand when heated in the cylinder. One of the reasons for copper cylinder overflow could be that the thermostat is set to a high temperature, and it is leaking because the water is too hot. Lower the temperature on your thermostat to fix this.

Another reason for overflow could be the perforation of the coils, due to which water leaks into the main cylinder. When this happens, the central heating water can mix with the boiler’s hot water. The only solution for this is to replace the copper cylinder.

Overflow Pipe from Sink

Sink or bathroom pipes overflow inside. The overflow pipe of the bathroom sink is located at the back of the basin, below the sink, opening in a drain. Just pull the plug and let the bowl drain if you notice the sink overflowing.


Some issues related to overflowing pipe leaking might require professional help or skills. However, you can fix an overflow pipe leaking in some cases by yourself. Keep checks on water coming out of the overflow pipe, identify its reason, and fix it with the above solutions.