Understanding Boiler Pressure in Bordon Homes
Living in Bordon and the wider GU35 area means you rely on a consistent heating system through the colder months. If you’ve noticed your boiler gauge dipping every time the heating comes on, it can be both frustrating and worrying. Pressure fluctuations often point to an internal issue, and one of the most common culprits is a faulty expansion vessel. In this guide, we’ll explain what an expansion vessel does, how it can cause your boiler pressure to drop when the heating turns on, and what steps you can take to remedy the situation.
The Role of the Expansion Vessel
An expansion vessel is a key component in sealed central heating systems. As the water in your system heats up, it expands. Without a vessel to accommodate this extra volume, pressure would spike, risking leaks or damage to your boiler. The expansion vessel contains a rubber diaphragm dividing the internal space into water and air chambers. When working correctly, it absorbs excess water pressure, ensuring your boiler maintains a steady reading, typically between 1 and 1.5 bar when cold.
How Expansion Vessel Faults Cause Pressure Drops
When an expansion vessel fails—often due to a ruptured diaphragm or a loss of air charge—the space that should cushion expanding water fills completely. Once the system heats up and the water expands, there’s nowhere for the extra volume to go. This causes pressure to spike momentarily, triggering the safety valve to release water. After the valve opens, you’ll see your boiler pressure drop below optimal levels, even when the heating is still running. Over time, repeated water loss leads to constant top‐ups and an ongoing pressure issue.
Common Signs Your Expansion Vessel Needs Attention
- Pressure gauge drops below 1 bar every time the heating comes on.
- You hear water discharging from the pressure relief valve.
- Frequent requirement to re‐pressurise the system.
- The expansion vessel feels waterlogged—when tapped, it sounds solid rather than hollow.
Troubleshooting Expansion Vessel Problems
Before calling in a professional Gas Safe engineer, you can carry out some basic checks and simple fixes. Here’s how homeowners in Bordon, Alton or Liphook can troubleshoot:
- Check the Air Charge: Locate the Schrader valve on the expansion vessel and use a tyre pressure gauge to measure the air side. It should be around 0.8 bar. If it’s significantly lower, you can use a bicycle pump or car tyre inflator to top it up.
- Inspect for Waterlogging: Tap the vessel. A hollow sound indicates there’s still air inside; a dull thud suggests it’s waterlogged and needs either recharging or replacement.
- Re‐pressurise the System: If the system has lost pressure, follow your boiler manual to isolate and refill the system to the recommended level. Many boilers in GU34 and GU32 areas come with simple filling loops.
- Bleed Your Radiators: Sometimes trapped air elsewhere in the system causes odd pressure changes. Bleed each radiator, starting at the lowest point in your home, to remove air pockets.
When to Call a Gas Safe Engineer
If your DIY checks don’t resolve the issue, it’s time to get professional help. An experienced Gas Safe engineer can:
- Test the vessel’s internal diaphragm for leaks using specialist tools.
- Replace a faulty expansion vessel or install a larger one if you’ve extended your heating system.
- Perform a full boiler health check to ensure no other components are contributing to pressure loss.
Regular boiler servicing helps catch expansion vessel issues early, reducing the risk of a heating breakdown and unexpected repair costs.
Preventative Tips for Bordon and Farnham Homeowners
Preventing pressure drops is easier with a proactive maintenance routine. Here are some expert tips for homes across Bordon, Farnham, Petersfield and the surrounding areas:
- Schedule Annual Servicing: An annual service by a Gas Safe engineer not only checks your expansion vessel but also verifies overall boiler performance.
- Monitor Regularly: Keep an eye on your gauge. A steady drop over months often signals a slow leak or vessel issue.
- Invest in Cover: Consider a comprehensive boiler cover plan to reduce unexpected costs and ensure priority response in case of emergency.
- Upgrade When Needed: If you’re replacing an old system or rearranging radiators, a new, correctly sized expansion vessel avoids future pressure headaches. Ask about our new boiler installation options.
Expanding to Nearby Areas: Liss, Grayshott and Haslemere
Homes in GU30 and nearby postcodes often share similar heating setups. If your property in Liss or Grayshott experiences unexplained pressure dips, the same expansion vessel checks apply. As always, professional support from a local Gas Safe engineer ensures a safe and reliable fix.
Frequently Asked Questions
- Q: How often should I check my boiler pressure?
A: Aim to check the gauge once a month, especially before and after the heating season. - Q: Can I replace the expansion vessel myself?
A: While you can re‐pressurise the air charge, replacing the vessel involves draining the system and handling gas components. Always consult a Gas Safe engineer. - Q: Does a larger heating system require a bigger expansion vessel?
A: Yes. If you’ve added multiple radiators or extended your home, you may need a vessel with greater capacity. - Q: What happens if I ignore pressure drops?
A: Continued low pressure can stress your boiler, lead to cold spots in radiators and eventually cause a heating breakdown.
If you need help with your heating or boiler, our local engineers are here to help. Call us on (01420) 558993 or book online at embassygas.com/book
Written by Embassy Gas — your local heating experts covering Bordon, Alton, Liphook, Farnham and surrounding areas.