Toilet Inlet (Fill) Valve Leaking

Leaking outside the cistern or inside it?

The inlet valve, also called the fill valve or float valve, is the part that lets water into the cistern after a flush and shuts off when the float rises. It can leak in two quite different ways, and they need different fixes.

If water is getting out of the cistern onto the floor or down the pipe, that is an external leak at one of the valve’s joints, and this page covers it. If the valve keeps letting water in so that it runs into the bowl or out of an overflow pipe, the valve is failing to shut off. That is covered in a toilet refill valve leaking.

To tell them apart, look underneath the cistern where the supply pipe meets it. Water there, or on the pipe below, is external. A dry pipe with a constant trickle into the pan is the valve not shutting.

Find the joint in three steps

Turn off the isolation valve on the supply pipe. It is usually a small valve just below the cistern with a screwdriver slot; turn the slot so it sits across the pipe. Dry the valve tail, the nuts and the pipe with a towel. Turn the isolation valve back on and hold a folded piece of dry tissue against each point in turn.

• The connector nut where the supply pipe or flexible hose screws onto the valve tail. A drip here is usually the fibre or rubber washer inside the nut.
• The large plastic back nut that clamps the valve to the cistern. A leak here, or a ring of water around the hole, means the rubber seal inside the cistern has shifted or perished.
• The flexible hose itself. Rust spots on the braid, a bulge or a kink mean the inner tube is failing.
• The isolation valve and its two compression nuts. A weep around the slot shows up soon after someone has turned it.

A flexible hose that is swollen, rusty or spraying is not a tightening job. Leave the isolation valve off, or shut the main stopcock, and replace the hose before you turn the water back on.

Fixing a drip at the connector nut

This is the most common inlet valve leak and the easiest to fix. Most modern flexible hoses have a rubber washer built into the nut. Copper pipes usually connect with a tap connector that takes a fibre washer, which hardens and shrinks as it dries.

With the isolation valve off, flush the toilet and hold the handle down to empty the cistern. Put a small container under the joint, undo the nut and check the washer. If it is flattened, cracked or hard, replace it with one of the same size. Most toilet inlet valves in the UK take a 1/2 inch connection, so a standard 1/2 inch fibre or rubber washer is right in most cases. Refit the nut hand-tight, then no more than a quarter turn with a spanner while holding the valve tail still. Turn the water back on slowly and check with dry tissue.

Resist the temptation to wrap the thread in PTFE tape and crank it tight. On a joint that seals with a washer, tape on the thread does nothing, and over-tightening a plastic tail is a quick way to crack it. A cracked tail cannot be repaired; the whole valve has to be changed.

When the valve itself has to be replaced

Replace the valve if its tail is cracked, if the seal through the cistern still leaks after the back nut has been firmly hand-tightened, or if it is old and also slow to refill. Inlet valves are cheap. A universal bottom-entry or side-entry valve typically costs £8 to £25 from a merchant. Common replacements come from makers such as Fluidmaster, Siamp and Thomas Dudley, and many are adjustable in height to suit different cisterns.

Check which type you have before buying. A bottom-entry valve comes in through the base of the cistern, with the supply pipe underneath. A side-entry valve comes in through the side wall, near the top, and is common on older and low-level cisterns. The two are not interchangeable without changing the pipework. Also check whether your cistern is fed from the mains or from a cold water tank in the loft, because some valves need a different setting or insert for low pressure.

The swap itself is: isolate, empty the cistern, undo the supply connector, undo the back nut, lift the old valve out, fit the new one with its seal inside the cistern, tighten the back nut by hand, reconnect and set the float so the water stops at the fill line marked inside the cistern. How to repair a leaking cistern covers the other cistern parts you may find worn at the same time.

When an inlet leak becomes an emergency

Most inlet valve leaks are slow drips that stop the moment the isolation valve is turned off. It is urgent if a hose has burst, if the isolation valve will not turn or will not stop the flow, or if the toilet is upstairs and water is reaching the ceiling below.

In any of those cases shut the main stopcock. How to turn off a stopcock covers where to find it and what to do if it is stiff. Our toilet repair visit starts with the £60 call-out at any hour, and the repair price is agreed with you on site before any work starts. As a typical market guide, replacing an inlet valve or a flexible hose usually costs in the region of £80 to £150 including a standard part.