A running cistern wastes water and an unreliable flush can make a toilet unusable. We look at the symptoms, the type of cistern and the available access before proposing a repair.
Match what you notice to the parts we would check. Toilet designs vary.
1 Fill valve
The cistern won’t fill or won’t stop filling
This valve lets water in after a flush. Its float tells it when to stop. We check the supply if the cistern stays empty, and the float and shut-off if it keeps filling.
Fluidmaster 400UK073 bottom-entry fill valve
This example uses a ½-inch bottom inlet. A cistern fed through the side needs a side-entry type, such as the Fluidmaster 747UK where compatible. We also check the available height and float clearance.
The valve releases the stored water when you flush. If the seal at the bottom won’t close, water can keep trickling into the bowl.
Fluidmaster PRO550UK cable flush valve
This dual-flush example is designed for 1½-inch and 2-inch outlets. We also check the overflow height, lid clearance and how the button operates. A sound valve body may only need the correct replacement seal.
The button operates the flush through a cable, rods or another link, depending on the cistern. We check the control and the connection.
Fluidmaster C220 chrome-effect cable button
The C220 fits the manufacturer’s 550-series cable valves. A similar-looking button can use rods or an air tube instead. We check the existing mechanism and the opening in the lid or panel.
Tell us whether the puddle appears when the toilet is idle, refilling or flushing. The supply, a cistern seal or the waste connection may need checking.
The fill or flush mechanism may be failing. Tell us whether it runs continuously or only after some flushes.
The button or handle does very little
We check the controls and the flush mechanism. A slow refill can also affect the next flush.
Water appears at the base or cistern
A leak when flushing may come from a different place to a leak that continues while the toilet is idle.
There is water on the floor behind the toilet
Water can run down from the inlet hose, cistern or the seal between the cistern and pan. If it appears only during a flush, the flush connection or pan connector may also need checking.
The pan water rises after flushing
Rising water that drains slowly points towards a blockage or a waste problem. Stop flushing while it is rising and mention any other outlets that are backing up.
The toilet rocks or the pan is cracked
A loose WC can strain its waste connection. If the pan is damaged or water is escaping, stop using it and tell us whether another toilet is available.
Where is the water?
01A trickle inside the bowl
If the cistern fills high enough for water to reach its overflow, we check the fill valve and float. If the water level stays below the overflow and the bowl still trickles, we check the flush valve and its seal.
02Water outside the bowl or under the cistern
Whether the floor gets wet while the toilet is idle, refilling or flushing helps separate a supply-side leak from a flush seal or waste connection.
03A flush that is weak or missing
Tell us whether too little water enters the bowl or whether the bowl fills up and then drains slowly. We check how the cistern releases water for the first symptom and look towards the waste outlet for the second.
What we can do
We can replace suitable fill and flush valves, investigate leaking supply connections or pan connectors, and remove, refit or replace a WC to an agreed scope. For a concealed cistern, we check what can be reached through the access panel.
Parts we may check or replace
These are examples. We check what is fitted before choosing a replacement.
Fluidmaster 22103 close-coupling kit
On some toilets with the cistern sitting directly on the pan, water appearing between them during a flush can point to the coupling seal. This kit is for a 1½-inch cistern outlet. We check the seal shape, fixings and where the water starts.
This joins the back of the toilet pan to the soil pipe. If water appears at that joint when flushing, we check the pan outlet, pipe size, offset and available depth. The correct seal and shape depend on the installation.
Tell us if it is your only toilet, whether water is escaping and how the cistern is accessed. A photograph of the toilet or flush plate can help identify the type.
Send a photo of the whole toilet and the flush button or wall plate. It helps us identify the layout and discuss access before a visit.
A cistern you can see
If the cistern sits on the pan or is mounted visibly on the wall, its working parts can usually be reached through the top. The space around it and the pipe connections can still affect the job.
A cistern in a furniture unit
On some back-to-wall toilets the floor-standing pan blocks removal of the front panel. We check the access first. If the pan needs to come out to remove that panel, we agree the extra work and how it will be refitted.
A separate cistern behind boxing or tiles
We check whether the existing opening reaches the faulty part. Some cisterns can take compatible standard valves. If a larger part or the cistern itself cannot come out through the opening, we discuss what needs to be opened and agree the scope before work.
The frame supports the pan and houses the cistern. We identify the model before ordering a part and check the manufacturer’s compatibility list. Some parts can be serviced through the flush plate. Work beyond that opening can require access through the boxing.
The flush pipe carries water from a separate cistern to the toilet pan. Either end can leak, at the cistern outlet or where the pipe enters the pan. We check those seals as well as the separate waste connection. Reaching a hidden seal can mean removing the pan or opening part of the boxing.
Planning your visit
What happens next
01
Describe the job
Send your postcode, what is happening and a photo if it helps. Tell us if water is still escaping.
02
Agree the visit
We confirm availability and explain the basis of any attendance or investigation charge before booking.
03
Agree and check the work
We explain what we find, agree any further work and check the affected plumbing afterwards.
Common questions
Can you replace just the faulty part?
Often that is possible when the fitting is accessible and compatible parts are available. We will explain the options if more of the assembly needs replacing.
What if the cistern is hidden behind the wall?
A photo of the flush plate can help. We’ll check the opening behind it and discuss any additional access required before work.
Can you give me an estimate?
We discuss the work and the basis of any attendance or investigation charge before booking. Where the fault or access is uncertain, we may need to assess it first. We discuss any change to the agreed scope before additional work.