Toilet Keeps Running: Causes, Checks & Fixes

Isolate the toilet supply if water is overflowing or leaking continuously

Close the local isolation valve if safe. Do not force seized valves, keep water away from nearby electrics, and stop using the toilet if wastewater or a loose pan connection is escaping.

MOST LIKELY CAUSES

Start with these

Flush valve seal leaking Water passes continuously from cistern to pan.

Fill valve not shutting off The cistern keeps topping up.

Water level too high Water runs into the internal overflow.

Button or cable sticking The flush valve may remain slightly open.

◫ Symptom variations Match the exact cistern or flushing behaviour. ⌄

Water trickles into pan
Cistern refills every few minutes
Running stops when float is lifted
Water reaches overflow level
Button feels slow to return

✓ Quick checks Simple observations before dismantling the cistern. ⌄

Check whether the cistern contains water.
Observe whether the fault happens during filling, flushing or while idle.
Check the local isolation valve and visible inlet connection.
Look for water entering the pan continuously.
Operate buttons and handles gently without forcing them.

If the cause is obvious: keep the water isolated until the correct part is repaired or replaced.

If the toilet leaks or overflows: stop using it and call a plumber if isolation is unreliable.

1 Step 1 — Check the cistern water level Inspect the cistern carefully before replacing parts. ⌄

Process

Remove the lid carefully and observe whether water is entering the overflow.

Success looks like: An overfilling fault is confirmed.

Escalate when: If the level is normal, the flush seal is likely leaking.

2 Step 2 — Lift or support the float gently Inspect the cistern carefully before replacing parts. ⌄

Process

See whether the inlet flow stops when the float rises.

Success looks like: The fill valve can shut off.

Escalate when: If it continues, the fill valve needs cleaning or replacement.

3 Step 3 — Check the flush mechanism returns fully Inspect the cistern carefully before replacing parts. ⌄

Process

Operate the button once and make sure the valve drops back into place.

Success looks like: The running stops after the mechanism reseats.

Escalate when: If not, the seal or button linkage needs attention.

⌁ Common causes explained Why cistern and flush faults develop. ⌄

A toilet that keeps running usually has a leaking flush valve seal, overfilling cistern, faulty fill valve, incorrect float setting or a flush button that is not releasing fully.

Toilet mechanisms use small seals, floats, cables, valves and moving linkages. Scale, wear, poor adjustment and loose connections can produce several similar symptoms.

⌘ Advanced diagnostics Plumber-level checks and repair work. ⌄

Clean or replace the flush valve seal.
Adjust or replace the fill valve.
Check internal overflow height and float setting.
Inspect button cable or pneumatic tube.
Descale valve seats and confirm final shut-off.

▣ Parts that may need replacing Common components linked to this fault. ⌄

Flush valve seal
Flush valve
Fill valve
Button or cable
Pneumatic tube
Cistern washer

! When to call a plumber Conditions that should end basic troubleshooting. ⌄

The isolation valve will not close or is leaking.
The cistern, pan or flush pipe is cracked.
Wastewater is escaping at the toilet base.
The toilet is loose or moving on the floor.
Internal parts are inaccessible behind a concealed cistern.
The fault returns after adjustment or seal replacement.

? Frequently asked questions Common questions about toilet faults. ⌄

Why does the toilet refill every few minutes?

A leaking flush valve usually lowers the cistern level and makes the fill valve open again.

Can limescale affect a toilet cistern?

Yes. Scale can restrict fill valves, prevent seals closing and make moving parts stick.

Should I force a stiff isolation valve?

No. A seized valve can leak or break. Use the main stopcock or call a plumber if necessary.