A failing fill valve, the modern replacement for the older brass ballcock, is one of the most common causes of a continuously running toilet, a hissing cistern, and an overflow pipe dripping outside the property. The valve sits in the cistern, opens after a flush to refill the chamber, and closes when the water reaches the set level. When the diaphragm perishes or the float arm sticks, the valve never seals, water continues to enter the cistern, and the surplus runs out through the warning-pipe overflow. Over a year, a continuously running fill valve can waste in excess of 100,000 litres of metered water and is a top-three cause of unexplained water-bill spikes in London property.
We replace traditional brass Part 2 ballcocks and modern WRAS-approved bottom-entry or side-entry fill valves on every cistern type we encounter: low-level, close-coupled, concealed-cistern wall-hung, and the older high-level Edwardian flushpipe suites. Common modern replacements include the Fluidmaster PRO, Torbeck quiet-fill, and Siamp Compact diaphragm valves, all of which fit a standard 15mm tail with a Type AG air-gap to BS6730 to comply with current Water Regulations. Where the float arm or seat is the issue rather than the valve itself we fit a service kit. Where the body is brass with a perished washer we will normally recommend replacement with a modern adjustable diaphragm valve for quieter operation and a longer service life.
Where this service applies
- Overflow pipe dripping or running continuously outside the property
- Cistern hissing or refilling at random times when the toilet has not been used
- Cistern slow to refill, taking 90 seconds or more after a flush
- Water level in the cistern too high or too low for a clean flush
- Brass Part 2 ballcock seized, washer perished, or float arm bent past adjustment
- Concealed-cistern wall-hung WC where access to the valve is through a removable panel
- Cistern water level dropping overnight, fill valve cycling on and off as the flush valve also leaks
- Water-bill spike with no obvious leak, fill valve cycling unnoticed in a guest WC
- Upgrade to a quiet-fill valve where cistern noise wakes occupants at night
How we deliver
No surprises, no upselling. The exact path every job follows.
- 1
Symptom triage
We confirm the fault is the fill valve (rather than a leaking flush valve or a cracked cistern) by isolating supply and watching the cistern level over five minutes. A falling level with the supply off points to the flush valve, a steady level with supply on but no flush points to the fill valve. - 2
Isolation at the service valve
Cistern supply isolated at the in-line service valve (or at the BS1010 stop-tap where no isolator is fitted), and the cistern drained by holding the flush. We fit a new quarter-turn isolator on the supply as part of the visit where one is missing. - 3
Lid off and access opened
Close-coupled cistern lid lifted, or panel removed from a concealed wall-hung frame. We protect the floor with sheet and absorbent matting before disconnecting any supply line. - 4
Old valve removed and back-nut inspected
Supply tail disconnected, the old ballcock or fill valve back-nut undone, and the unit lifted out. The cistern wall around the valve seat is checked for hairline cracking, which is a common find on older porcelain. - 5
New WRAS-approved fill valve fitted
A modern Fluidmaster PRO, Torbeck quiet-fill, or Siamp Compact diaphragm valve fitted with a new top-hat washer on the inside and outside of the cistern wall, and the air-gap maintained to Type AG to BS6730. - 6
Water level calibrated
Service valve reopened, cistern allowed to fill, and the float arm or adjustment screw set so the water sits 20mm below the warning-pipe overflow. Flush volume tested and timed. - 7
Cistern cycled and signed off
The toilet is flushed three times to confirm clean refill, quiet operation, and no continuing trickle into the overflow. The lid is replaced and the area wiped down.