Vaillant Boiler Expansion Vessel 10L 181051 with PRV 178985

This vaillant expansion vessel 10l 181051 and prv 178985 absorbs heating-system pressure changes so your vaillant boiler runs safely and steadily. Over time, the internal diaphragm can fail or lose charge, which can cause pressure drops, frequent topping-up, PRV discharge/pipe dripping, and lockouts. Replacing the correct vessel helps stabilise system pressure, reduces nuisance shutdowns, and restores reliable heating and hot water performance.

Compatibility :

• ecoMAX (System/Combi): 613, 613/2, 618, 618/2, 622, 622/2, 635, 824, 824/2, 828, 828/2, 835
• ecoTEC Exclusive: 832, 835, 838, 843
• ecoTEC Plus (System/Combi): 612, 615, 618, 624, 630, 637, 824, 825, 831, 832, 835, 837, 838, 937, 938
• ecoTEC Pro: 22, 24, 28, 30
• Home (Combi/System): Combi 25, 30, 35 | System 12, 15, 18, 25
• Other listed variants: Exclusive 627 | VWZ MEH 61

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 (FAQ’s)

1. What does an expansion vessel do in a Vaillant boiler?
It absorbs pressure expansion when water heats up. This keeps system pressure stable and helps prevent the PRV from releasing water.

2. What are the common signs of a faulty expansion vessel?
Pressure rising close to 3 bar when heating is on, PRV discharge pipe dripping, frequent topping up, and pressure dropping again after cooling.

3. Can a bad expansion vessel cause the PRV to leak?
Yes. If the vessel has lost charge or the diaphragm has failed, pressure spikes can force the PRV to open. After that, the PRV may continue to drip.

4. How do I know if it’s the PRV or the expansion vessel?
If pressure shoots up when heating runs and you see discharge outside, it often points to the expansion vessel. If it drips even at normal pressure, the PRV may be worn or have debris on the seat.

5. Why does my boiler keep losing pressure after I top it up?
Common causes are PRV discharge, a failed expansion vessel, small leaks on radiators/valves, or air being released after topping up.