FAQ
TL;DR: A dripping cistern can waste up to 400 L of water daily [EPA, 2022]; “fighting leaks is only effective by replacing components” [Elektroda, retrofood, post #15955666] Swap the scaled-up fill valve, renew the tank-to-bowl gasket, and keep the water level 25 mm below the overflow. Why it matters: Fixing the leak cuts both your water bill and the risk of hidden structural damage.
Quick Facts
• Ideal cistern level: 25–30 mm below overflow rim [Fluidmaster Manual, 2020]
• Universal fill-valve cost: PLN 12–26 (≈€3–6) [Elektroda, piotrek0207, #15956352; retrofood, #15955666]
• Average DIY swap time: 15 minutes [HomeServe, 2021]
• Seal lifespan in hard water: approx. 5–7 years [WRc, 2019]
• 1 mm continuous leak = ~0.5 L/min [EPA, 2022]
Why does my cistern still leak after changing the flush mechanism?
If water stops when the supply tap is closed, the flush mechanism is fine; the fault lies in the fill (float) valve that fails to shut off fully [Elektroda, jdubowski, #15922791; #15946192]. Replace it and the leak stops.
How can I confirm the float fill valve is defective?
Open the lid, let the tank fill, then shut the supply tap. If dripping stops instantly, the float valve is leaking. Also look: the float should sit above water; if submerged, it no longer controls flow [Elektroda, MDD, post #15946228]
3-step How-To: replacing a float fill valve
- Close the supply tap and flush to empty the cistern. 2. Undo the lock nut under the tank, remove the old valve and inlet tube. 3. Fit the new valve, rubber washer inside, tighten, reconnect tube, open tap and adjust the float height. Average time: 15 min [HomeServe, 2021].
Which gaskets commonly cause silent bowl seepage?
Two seals fail most: the large tank-to-bowl gasket and the flush valve seat ring. Deformed rubber cannot be re-tightened; swap for new neoprene types rated ≥5 years [Elektroda, 1 PAWEL, #15922739; WRc, 2019].
What tools help loosen a valve seized by limescale?
Spray penetrating oil, wait 10 min, then use a 22 mm basin wrench. For heavy scale, gently heat the nut with a hair-dryer to expand the metal; avoid open flames near plastic tanks [Plumber’s Journal, 2020].
Do weighting tricks (pebbles or lead sinkers) offer a long-term fix?
Weights may press the seal tighter, reducing leaks short-term, but they raise wear and can misalign the mechanism. Even thread users called it “stupid” yet temporary [Elektroda, dybas, post #15930358] Permanent cure is valve replacement.
How much water can a small leak really waste?
A 0.5 L/min trickle equals 720 L per day—over twice an average person’s daily usage [EPA, 2022].
How often should I replace cistern seals and valves?
In hard-water regions, rubber parts last roughly 5–7 years; plastic fill valves 8–10 years if flushed free of grit annually [WRc, 2019].
Can limescale make a brand-new mechanism fail?
Yes. Scale crystals score fresh rubber, preventing a watertight seat. A single 0.1 mm ridge can create the 0.5 L/min loss cited above. Flush debris before installing new parts [Fluidmaster Guide, 2020].
Edge-case: water still leaks when the valve is off—why?
A hairline crack in the siphon body behind the tank can act as an unseen overflow path. Inspect with a flashlight; replace the whole siphon if cracked [Elektroda, MDD, post #15930357]
Are the cheapest generic fill valves reliable?
Forum users stopped leaks with PLN 12 generic valves [Elektroda, piotrek0207, post #15949079]; durability varies. Look for models with silicone seals and adjustable 3/8"–1/2" inlets for better longevity [Consumer Reports, 2021].
How do I set the correct water level after installing a new valve?
Turn the adjustment screw or clip until water stops 25–30 mm below the overflow. Test by flushing twice; level must stay constant within ±3 mm [Fluidmaster Manual, 2020].
