Vaillant EcoTec Pro | How To Change The Expansion Vessel

Breakdown & Wiring Book: https://book.advancedboilertraining.c...

REASONS WHY YOU MIGHT NEED TO CHANGE THE EXPANSION VESSEL:

- The main reason you would need to change the expansion vessel would be because it has split internally. The expansion vessel should have two sides internally, one full of water and one full of air. When water heats it expands causing the rubber diagram inside to press against the air side. If the expanding water pressure didn't have anywhere to go then it would just activate the PRV (pressure release valve) and then leave the boiler.

This is what happens when the rubber diagram in the vessel splits, it loses the ability for the water to push against the air side and instead when the pressure increases too high it activates the PRV.

Usually the first sign you would notice would be the boiler losing pressure from the PRV. Upon further inspection you would attach a pressure gauge to the expansion vessel and you would notice it's empty.

Another first sign you might notice would be no hot water or heating as the boiler requires some pressure to operate and if most of the pressure has been lost from the PRV (pressure release valve) then the boiler will not operate.

Getting your boiler serviced every year can prevent this as on its annual service the engineer would check the vessel pressure.