Just moved in and need to re-do air gap, but there are two valves!? Help!

[Gemma_1985]

Hello

I have just moved into my new house and I am a bit confused by the heating system, before I had a combi which I understood ok but in this one I have an Albion hot water tank, that is leaking a little from the pipes circled.

after reading a lot online it looks like I need to re do the air gap, but all the videos etc I have seen only show the cylinder having one valve, but I have two!? why is that? What is the process to do it with two valves? I think the top one says TRV?

any help appreciated

G x

 

[Hugh Jaleak]

You have there an 'unvented' (mains pressure), hot water cylinder. The valves in question are a TRV (Temperature Relief Valve) and PRV (Pressure Relief Valve), you will need a Plumber with a 'G3' certificate which qualifies them to work on unvented hot water systems to look at it I'm afraid.

DIY is not an option with these things for safety reasons.

 

[TCCHeating]

You are allowed to to reinstate the air gap without a g3 certificate.

The top valve is a tprv. It will open in an overheat situation as well as overpressure. (Usually about 9 bar)

The lower valve is a prv. (Usually opens about 6 bar).

Why are there 2? Bolt and braces. Have a look at the myth busters video on YouTube of an invented cylinder exploding and you will appreciate why you cannot have too many safety devices on these things.

Megaflo cylinders have a guide to do this on their website. It should be a similar process on your cylinder,

 

[Agile]

Does it really have an air gap?