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Brian, HVAC Technician
Category: HVAC
Satisfied Customers: 863
Experience:  OFTEC registered oil heating engineer and plumber.
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Vaillant boiler 828e installed new in 2005. still works fine

Customer Question

vaillant boiler 828e installed new in 2005. still works fine but have problem holding pressure. in the last 2 years as indicated on pressure gauge. pressure falls and so have to open valves to pressurise. recently i switched it off while on holiday for i week. on return, pressure this time was high and had to relieve it. pressure is changing nearly ever day now and have to constantly adjust. i can see no leaks anywhere.
Submitted: 2 years ago.
Category: HVAC
Expert:  Brian replied 2 years ago.
Hi this will be the expansion vessel. it either need pressurizing or its perished inside.
Page 9 of this manual will guide you to where its located.
You are looking for the Expansion vessel valve. Its a Car Tyre Valve. you need to take the cap off and push it in as if to let air out if water comes out its broken and needs replacing.
If you just get air out.
Isolate the boiler let the pressure/water out of the boiler and pump the expansion vessel up to what ever it states in the manual. if you cant find it anywhere pump it to 1bar.
Open the boiler valves and refill with water to 1.2 bar, this should then cure the fluctuation in pressure.