NANDIX Repairs · Plumber
Water tank overflowing or not filling
A tank that overflows usually has a worn float valve. A tank that does not fill may have a stuck valve, an air lock or a pump problem.
What usually causes it
- Worn washer or broken arm in the float (ball) valve.
- The float is set too high or is cracked and full of water.
- An automatic level controller with a faulty sensor.
- For tanks that do not fill: a blocked inlet, an air lock or a pump that runs dry.
What you can check yourself
- Lift the float arm by hand: if the water stops, the valve works and the float needs adjusting.
- Shake the float: water inside means it is cracked.
- Check the overflow pipe runs to a drain, not onto a wall.
Parts to ask the shop for
- Float valve of the same inlet size (½ inch or ¾ inch is common)
- Float ball
- Water level controller or sensor, if fitted
Take the old part or a photo of it: sizes and threads must match.
What to ask the worker
- Is it the valve, the float or the controller?
- Can the float be adjusted instead of replaced?
- If you suggest a level controller, which type, and where will the sensors go?