How to Repressurise your Heat Pump

Keeping the right pressure in your heat pump system is essential for efficient heating and reliable operation. Low system pressure can lead to poor heating performance, system shutdowns or increased energy use — but the good news is that, in many cases, you can safely top it up yourself. Below is a clear step-by-step guide on how to repressurise your heat pump system.

Note: Always check your heat pump or system manual for model-specific details before attempting any adjustments.

📹 Watch: How to Repressurise Your Heat Pump

Why Pressure Matters in Your Heat Pump System

Your heat pump circulation system contains water that transfers heat throughout your home. Just like a conventional boiler, this sealed system relies on the correct pressure to circulate water properly:

• If pressure is too low, the heat pump may struggle to circulate heat, radiators or underfloor circuits may heat unevenly, and the system could shut down.
• If pressure is too high, it could stress system components.
  
  For most systems, a cold pressure reading of around 1.0 bar is typical when the system is off or cold — similar to conventional heating systems.

When Should You Top Up Pressure?

You’ll typically need to repressurise if:

✔ The pressure gauge drops below the manufacturer’s recommended level (often ~1.0 bar).
✔ You’ve recently bled radiators or carried out maintenance that let air out of the system.
✔ Your heat pump controller indicates a “low pressure” warning.

Remember — frequent pressure loss can signal a leak or component issue, so if pressure drops often, seek professional help.

Step-by-Step: How to Repressurise Your Heat Pump

⚠️ Safety first: Always switch off your heating and allow the system to cool before topping up pressure. Never hang valves open once the correct pressure is reached.

1. Locate the Filling Loop

Most systems (including many heat pumps with hydronic heating circuits) have a filling loop — a small flexible connector between the mains water and the heat pump’s sealed system.

2. Turn Off the Heat Pump

Make sure the system is off and cool. This ensures you’re reading pressure accurately.

3. Read the Pressure Gauge

The pressure gauge will show system pressure in bars. A typical cold system target is around 1.0 bar (check your manual for your model).

4. Open the Filling Valve Slowly

Open the filling loop valve to allow water into the system. You should hear the water flowing and see the pressure rise on the gauge.

5. Watch the Gauge Carefully

Stop once you reach the recommended pressure. Don’t overpressurise — excessive pressure can cause issues.

6. Close the Valve and Secure It

Once the needle sits at the correct level, close the filling loop valves tightly and remove/disconnect the loop if necessary to avoid leaks.

7. Restart Your Heat Pump

Turn the system back on and check for correct operation.

Tips & Troubleshooting

✔ Check After Bleeding Radiators
If you’ve just bled air from radiators or the system, pressure will often drop — always recheck afterward.
✔ Monitor Regularly
Pressure can drift over time — check the gauge seasonally, especially before winter.
✔ Don’t Ignore Frequent Drops

When to Call a Professional

If pressure keeps dropping despite topping up, or if you notice:

• inconsistent heating;
• visible leaks;
• repeated error codes;

…it’s time to contact a certified heat pump engineer. Persistent pressure issues often indicate leaks or failing components.

In Summary

Repressurising your heat pump system is a simple maintenance task that helps maintain efficient heating and prevents avoidable shutdowns. With the right approach and a little care, you can keep your system running smoothly all year round.