If you can hear the ball valve in your loft tank turning on frequently, it’s usually a sign that something within your heating system isn’t stable. Many homeowners notice this as a repeated clicking or refilling sound, often when the heating has been running.
While it might seem like a minor issue with the tank itself, this behaviour is often a symptom of something happening elsewhere in the system.
Why the Ball Valve Keeps Activating
The ball valve controls the water level in your feed and expansion tank. It opens to allow water in when the level drops, then shuts off once the correct level is reached.
If it keeps activating, it usually means the water level is dropping more often than it should.
This typically happens when water is being lost from the heating system and needs to be replaced.
What This Usually Points To
In most cases, repeated activation of the ball valve is linked to ongoing water loss somewhere within the system.
What happens is:
Water escapes from the system
The tank level drops slightly
The ball valve opens to refill it
The cycle repeats over time
Because this process is automatic, it can continue for a long time without obvious visible signs inside the home. You can learn more about how this develops on our signs of a central heating leak page.
What People Often Assume
It’s common to think the ball valve itself is faulty. While that can happen, a faulty valve usually causes continuous filling or overflow — not repeated activation linked to heating use.
Another assumption is that small top-ups are normal. Occasional adjustment is expected, but frequent or repeated refilling is not.
If the valve keeps activating, it’s usually responding to a drop in water level rather than causing it.
How to Recognise the Pattern
Instead of focusing on the valve itself, look at when and how often it activates.
Ask yourself:
Does it happen more when the heating is on?
Has it become more frequent over time?
Are there other signs, such as air in radiators?
These patterns often point to water loss somewhere within the system.
What to Do Next
If your ball valve keeps activating, the focus should be on understanding why the water level keeps dropping.
The next step is to confirm whether water is being lost and identify where it is happening.
You can read more about the process on our how we find central heating leaks page, or view the full service on our Central Heating Leak Detection.
At The Leak Hunter, we trace the exact source of water loss within the system, allowing it to be resolved properly rather than repeatedly topped up or managed temporarily.
FAQ
Why does my loft tank keep refilling?
This usually happens because water is being lost from the system and the tank is replacing it.
Could the ball valve itself be faulty?
It’s possible, but repeated activation is more often a response to water loss rather than the cause.
Is this something I should be concerned about?
Yes. Frequent refilling usually indicates an underlying issue within the heating system.
Can this happen without a visible leak?
Yes. Many central heating leaks occur in hidden areas and do not show obvious signs.
Do you only cover my area?
If you’re outside these areas, don’t worry — our team covers most of the South East, providing trusted leak detection services throughout London, Kent, Sussex, and Surrey.
Final Thoughts
If your ball valve keeps activating, it’s rarely just a tank issue. It’s a clear sign the system is compensating for ongoing change.
Identifying the cause early allows the system to be stabilised properly rather than repeatedly correcting the symptom.