Toilet Cistern Not Filling or Keeps Running? How to Fix It (2026)
A cistern that will not fill leaves you with a toilet you cannot flush. One that keeps running wastes thousands of litres a month and empties your tank. Both are usually cheap fixes you can do in under an hour.
Quick answer: If the cistern will not fill, check the supply valve, then a blocked or stuck ball (float) valve. If it keeps running, the float is set too high (water escapes down the overflow) or the flush valve seal is worn. A new cistern ball valve costs KSh 350 on Buy More Mall.
Cistern Not Filling: Causes and Fixes
| Check | What you see | Fix |
|---|---|---|
| Supply / angle valve | No water enters at all | Open the valve fully; check the tank is not empty |
| Ball valve blocked | Only a trickle enters | Close supply, unscrew valve, clean out grit and sand |
| Float stuck | Arm jammed against the cistern wall | Free and re-align the float arm |
| Valve washer worn or valve cracked | Hissing but slow fill | Replace the ball valve |
| Low tank pressure | Every tap is weak | See the water-pressure guide below |
Cistern Keeps Running: Causes and Fixes
| Check | What you see | Fix |
|---|---|---|
| Float set too high | Water flows into the overflow pipe | Lower the float until water stops 2–3 cm below the overflow |
| Flush valve / flapper worn | Water trickles into the bowl constantly | Replace the seal or flush valve |
| Ball valve not shutting | Water keeps entering when full | Clean or replace the ball valve |
| Flush lever sticking | Valve stays partly open | Adjust or free the lever and chain |
How to Replace a Cistern Ball Valve
- Close the supply valve and flush to empty the cistern.
- Soak up the remaining water with a cloth.
- Undo the supply connector under the cistern.
- Unscrew the back-nut and lift the old valve out.
- Fit the new valve with its washer; tighten by hand plus a quarter turn.
- Reconnect the supply with thread tape on threads.
- Open the supply and set the float so water stops below the overflow.
- Flush a few times and check for drips underneath.
Parts and Prices
KSh 350
KSh 350
KSh 1,500
KSh 2,000
KSh 3,000
Some photos are reference images of the product type, used under open licences. Image credits are on each product page.
| Part | Use | Price |
|---|---|---|
| Ball Valve-Cistern | Cistern inlet valve | KSh 350 |
| Ball Valve-Toilet | Toilet inlet valve | KSh 350 |
| Top Flush Cistern | Replacement top-flush cistern | KSh 1,500 |
| Asian Toilet | Squat toilet | KSh 2,000 |
| P Trap Toilet | P-trap WC | KSh 3,000 |
Complete toilets: toilet prices in Kenya. Other bathroom fittings: bathroom and kitchen fittings.
Worked Example: A Running Toilet in a Rental Flat
A tenant reports that the roof tank empties overnight. The cistern is full, but water keeps flowing into the overflow pipe. The fix: lower the float arm (bend it gently or turn the adjustment screw) until water stops about 2–3 cm below the overflow. If it still runs, replace the ball valve at KSh 350. That is a small repair compared with a tank of wasted water every day.
Dye Test for Hidden Leaks
Put a few drops of food colour in the cistern and do not flush for 20 minutes. If colour appears in the bowl, the flush valve seal is leaking and needs replacing.
Common Mistakes to Avoid
- Over-tightening plastic nuts until they crack.
- Forgetting thread tape on the supply connector.
- Setting the float so high that water runs into the overflow.
- Ignoring a silent leak (use the dye test).
- Buying a valve without checking whether it is bottom- or side-entry.
Not sure which one fits? Send us your details on WhatsApp or through the product page and we will help you choose.
Frequently Asked Questions
Why is my toilet cistern not filling?
The supply valve is closed, the ball valve is blocked with grit, the float is stuck, or there is no pressure from the tank.
Why does my toilet keep running?
The float is set too high or the flush valve seal is worn.
How much is a cistern ball valve in Kenya?
A cistern ball valve is KSh 350 on Buy More Mall.
Can I fix a running toilet myself?
Yes. Adjusting the float or replacing the ball valve needs only basic tools.
How do I know if my toilet is leaking silently?
Add food colour to the cistern; if the bowl changes colour without flushing, the seal leaks.
Why does my cistern fill slowly?
Usually a partly blocked ball valve or low water pressure.
Prices shown are regular prices on Buy More Mall. Many products are currently on offer, so open the product page to see today's price.
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