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Tim Cooke
Tim Cooke,
Category: Appliance
Satisfied Customers: 1293
Experience:  Owner at Self-employed
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I have a Worcester Greenstar 29cdi combo boiler.There is a

Customer Question

JA: Hi. How can I help?
Customer: I have a Worcester Greenstar 29cdi combo boiler.There is a black unit attached behind the pump which has started to leak.The leak is fairly slow but causes a drop in the pressure even when you build it up.what is that unit called, is it repairable or has to be replaced?Also how do you have to remove the pump and how do you remove it?
JA: How old is your boiler? Where does the leak seem to be coming from?
Customer: About six years
JA: How long has this been going on with your boiler? What have you tried so far?
Customer: this problem has been for maybe a month but was only realised just a week ago
JA: Anything else we should know to help you best?
Customer: There is white button on the unit at the back of the pump.The button is a screw on type.When the button is tightened fully the leaking stops but as you start unscrewing it it starts.The leak is from inside the button.It is only drop a time.As the pressure drops the leak slows down but soon as you raise the pressure rate of the drops increases
Submitted: 14 days ago.
Category: Appliance
Expert:  Tim Cooke replied 14 days ago.

Good morning, and welcome to the Technical section in JustAnswer. My name is ***** ***** I will help you today. There's no time pressure on this topic - it will stay open for many days, and you can reply at any time. I will be away from my desk sometimes, but will respond as soon as I can.

The black unit is an AAV - automatic air vent. It isn't repairable, but it's easy to replace. The steps are:

1. Buy the part.
2. Turn off the boiler.
3. Isolate the boiler at flow and return valves.
4. Drain the boiler.
5. Replace the AAV.
6. Reverse step 3 and increase the system pressure if needed.
7. Turn on the boiler.
8. Have a self-congratulatory cup of tea.

Customer: replied 14 days ago.
To replace the AAV one has to remove the pump.To remove the pump does one have to remove the four Allen key screws and the pin or just the pin be good enough
Expert:  Tim Cooke replied 13 days ago.

You don’t have to remove the pump to replace the AAV on this boiler.