Baxi Boiler Expansion Vessel 10L Replacement Part

This baxi expansion vessel replacement helps absorb water expansion as your Baxi boiler heats up, keeping system pressure steady. Over time the diaphragm can weaken or fail, so pressure rises rapidly when heating, the PRV/discharge pipe may drip, or the boiler may need frequent re-pressurising. Replacing the correct vessel restores stable pressure control, helps prevent nuisance lockouts, and reduces the risk of repeat over-pressure problems.

Compatibility :

• Baxi Instant: 105 HE A
• Duo Tec HE: 24, 28, 33, 40
• Duo Tec HE A: 33 (Before/After Serial BTH1112), 40 (Issue 8)
• Baxi Combi HE: 33
• Platinum Combi HE: 24, 28, 33, 40
• Platinum Combi HE A: 33 (Before/After Serial BNE1112), 40 (Issue 4)

Important fitting advice

We recommend that all parts are fitted by a fully qualified Gas Safe registered engineer. If you need help confirming the right part, contact us our team has 10+ years of boiler spares knowledge and friendly chat support to help you quickly.

Delivery

At Boiler Spares Hub, we dispatch orders within 1 working day (Monday-Friday). Orders placed outside working days will be dispatched on the next working day. For delivery options available for this product, please add it to your basket or check our delivery options page.

Returns

We accept 30-day returns. Returns must be in an unopened, sealed box. If we find the item has been used or installation was attempted, we may refuse the return.

Frequently Asked Questions (FAQs)

1. What does an expansion vessel do?
It absorbs pressure changes as heating water expands, helping the boiler run at a stable pressure.

2. What are the common signs it needs replacing?
Pressure rises quickly when heating, PRV/discharge pipe dripping, frequent re-pressurising, pressure dropping after cooling, or pressure-related lockouts.

3. Does this fit all Baxi Duo-Tec boilers?
It fits the Duo-Tec models and more models listed in compatibility.

4. What does “Before/After Serial No.” mean?
It refers to a production change. The correct part can depend on whether your boiler serial number is before or after the stated serial break.

5. Will the vessel need pressure setting?
It’s pre-charged, but installers usually check/adjust the charge pressure to suit the system during fitting.