How Do I Top Up My Heating System? | J & S Plumbing and Heating, Lincoln
J & S plumbing and heatings guide – How Do I Top Up My Heating System?
Has your boiler pressure dropped?
Noticed your radiators aren’t warming up properly?
Don’t worry — topping up your heating system is often a simple fix!
At J & S Plumbing and Heating, we help homeowners in Lincoln and surrounding villages keep their homes warm and cosy all year round.
Here’s everything you need to know about how to top up your boiler pressure safely.
Why Does Boiler Pressure Drop?
Over time, it’s normal for your central heating system to lose a little pressure.
Some common reasons include:
Natural water loss over time
Bleeding radiators
Minor leaks or expansion vessel issues
If your boiler pressure is too low, your heating system might stop working properly — or even shut down completely.
What Does a Filling Loop Look Like – and Where Can I Find It?
Before you top up your heating system, you’ll need to locate your filling loop — the part that connects your boiler to your mains water supply.
Here’s what to look for:
In most homes, a filling loop is a small silver flexible hose (similar to a braided shower hose) with two small taps or valves. Top up by turning both valves in-line with the pipe.
Some newer boilers use keyed filling loops or keyless filling links instead. Full instructions on how to use these will be in your installation manual.
- Keyless filling loops: These have a built-in handle or lever that you simply pull without a key.
🛠️ Tip: If you’re not sure which type you have, check your boiler manual or call your local heating engineer.
Where Can I Find the Filling Loop?
Depending on your home and boiler model, the filling loop could be located:
Directly underneath the boiler — especially with combi boilers.
Inside an airing cupboard — if you have a system boiler with a hot water cylinder.
Hidden inside kitchen units — sometimes concealed behind cupboard panels near the boiler.
Attached externally to pipework — especially in older properties.
🛠️ Important:
If you cannot find the filling loop easily or it looks damaged, don’t attempt to top up the pressure — it’s safer to call a qualified engineer to avoid damaging your heating system.
How to Check Your Boiler Pressure
Find the pressure gauge on your boiler — usually a round dial with green and red zones.
Green zone: Ideal pressure (around 1.0 to 1.5 bar when cold)
Red zone: Too low or too high
If the needle is sitting below 1.0 bar, you’ll need to top up your heating system.
How Do I Top Up My Heating System? – Step-by-Step
Important: Always follow your boiler’s manual instructions, or call a qualified engineer if you’re unsure.
Here’s the basic method for most combi boilers:
Turn Off the Boiler
Let it cool for an accurate pressure reading and safe topping up.Locate the Filling Loop
Look underneath the boiler. You’ll find a silver flexible hose with two small taps or valves.Open the Valves Slowly
Gently open both valves to let water into the system.
You’ll hear water flowing.Monitor the Pressure Gauge
Watch the needle rise to between 1.0 and 1.5 bar.Close the Valves
Once you reach the correct pressure, close both valves tightly.Restart the Boiler
Turn your boiler back on and check it’s operating normally.
What If the Boiler Pressure Keeps Dropping?
If you find yourself topping up regularly, there could be a bigger problem, such as:
A hidden leak somewhere in the system
A faulty pressure relief valve
An expansion vessel issue inside the boiler
In these cases, it’s best to call a professional for a full heating system inspection.
Why Trust J & S Plumbing and Heating?
✅ Experienced, fully qualified heating engineers
✅ Fast, reliable appointments with set times (no waiting!)
✅ Honest advice and upfront pricing
✅ Local experts in Lincoln and surrounding villages
✅ Finance options available if major repairs are needed
✅ Qualified in Natural Gas, LPG, Oil, Unvented and Air Conditioning
Quick FAQs – How Do I Top Up My Heating System?
Q: Is it normal for boiler pressure to drop?
A: Small drops over time are normal. Frequent drops mean something needs attention.
Q: Can I top up the boiler myself?
A: Yes, most homeowners can safely top up their boiler following the correct steps. But if unsure, it’s always safer to ask a professional.
Stay Warm and Safe – Call J & S Plumbing and Heating
If you’re not confident topping up your heating system, or if your boiler keeps losing pressure, let the experts at J & S Plumbing and Heating help.
We’ll have your heating back to its best in no time.
📞 Book online today or call us for fast, friendly service!
