If you can hear a steady trickle of water feeding into your loft tank, especially when everything else in the house is quiet, it’s usually not something to ignore.
Many homeowners describe it as a faint but constant sound — not loud, but persistent. And while it might seem harmless, it’s often one of the clearest early signs that your heating system is losing water somewhere.
Why This Sound Matters
Your loft tank (feed and expansion tank) is designed to maintain the correct water level in your heating system. Under normal conditions, it should only refill occasionally.
If you can hear water trickling in regularly, it usually means the tank is repeatedly topping up to replace water that’s being lost.
A stable system should not need this level of ongoing adjustment.
What’s Likely Happening Inside the System
When water escapes from the heating system, even slowly, it creates a continuous imbalance.
What typically happens is:
The tank level drops slightly
The ball valve opens to refill it
The system is topped up automatically
The cycle repeats as more water is lost
This process can run continuously in the background, which is why the sound often becomes familiar rather than alarming.
Because much of the pipework is hidden beneath floors or behind walls, the source of the water loss may not be visible.
You can learn more about how these patterns develop on our signs of a central heating leak page.
What Homeowners Often Assume
It’s common to assume the noise is just the tank “doing its job” or that a small amount of refilling is normal.
While occasional topping up is expected, constant or repeated trickling is not.
Another assumption is that the issue lies with the tank or ball valve itself. In most cases, the tank is simply reacting to water loss elsewhere in the system.
How to Recognise the Pattern
Instead of focusing on the noise alone, look at how consistent the behaviour is.
Ask yourself:
Is the sound constant or becoming more frequent?
Does it happen more when the heating is running?
Are there other signs, such as air in radiators?
These patterns usually point to ongoing water loss affecting the system.
What to Do Next
If water is constantly trickling into your loft tank, the focus should be on understanding why the system keeps needing to be topped up.
In most cases, the next step is to confirm whether water is being lost and identify where it is happening.
You can read more about the investigation process on our how we find central heating leaks page, or view the full service on our Central Heating Leak Detection page.
FAQ
Is it normal to hear water trickling into the loft tank?
No. Occasional refilling is normal, but constant trickling usually indicates a problem.
Could this just be a faulty ball valve?
It’s possible, but in most cases the valve is responding to water loss rather than causing it.
Can there be a leak without visible water?
Yes. Many heating leaks occur in hidden areas and do not show obvious signs.
Will this get worse over time?
In most cases, yes. Ongoing water loss can lead to air entering the system and further instability.
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 you can hear water constantly feeding into your loft tank, it’s not just background noise — it’s a pattern.
Recognising that pattern early helps you identify what’s happening within the system and address it before it develops further.