A running toilet wastes a surprising amount of water, up to several hundred litres a day in a bad case, and on a water meter you are paying for every litre.

It is nearly always one of two parts, and both are cheap.

First, work out which of the two it is

Take the cistern lid off and look at where the water is going.

• Water is trickling into the pan continuously. The flush valve is not sealing, or the water level is above the overflow.
• The cistern keeps refilling and you can hear it topping up. The fill valve is not shutting off, or the float is set too high.

If the water level is too high

Water above the internal overflow simply runs into the pan forever. Adjust the float down so the water sits roughly 25mm below the overflow. On modern valves that is a screw or a clip on the float arm.

That alone fixes a good proportion of running toilets and costs nothing.

If the flush valve is leaking

The rubber seal on the flush valve perishes and stops sealing. Turn off the isolation valve on the supply pipe, flush to empty the cistern, and the seal can usually be replaced without removing the whole valve. Seals are a few pounds and match to the valve type, so take the old one with you.

If the fill valve will not shut off

Grit or limescale in the valve is the usual cause, particularly in hard water areas. Sometimes cleaning the diaphragm is enough. Often replacing the valve is quicker and more reliable.

The test that tells you for certain

When to call a plumber

• The isolation valve is seized and you cannot turn the water off
• The cistern or pan is cracked
• Water is appearing on the floor rather than in the pan
• It is a concealed cistern behind a wall or in furniture
• You have replaced the parts and it still runs

How Vantage can help

We cover Hertfordshire, Bedfordshire and Cambridgeshire, and a running toilet is a short job. If it is behind a panel or the isolation valve has seized, that is when it is worth calling someone.

Frequently asked questions

How much water does a running toilet waste?

In a bad case several hundred litres a day, which you pay for on a meter.

Is it the flush valve or the fill valve?

Use the food colouring test. Colour in the pan means the flush valve.

Can I fix it myself?

Usually yes. Both parts are inexpensive and accessible in a standard cistern.

Why does it happen in hard water areas?

Limescale stops valves seating properly. Cambridgeshire and north Hertfordshire are both hard water areas.

Want it sorted properly?

Anything past the free checks above needs a Gas Safe engineer with the right test kit. Ring Vantage on 01462 506374, any hour, any day of the year. You will get an honest arrival time rather than a comforting one, and the price before the work.

Where to next

• Leak detection
• Advice from our engineers
• Talk to a local engineer