Valve replacement on boiler?

[cartman44]

Hi All,

Hope you can help, I have a problem with my boiler in that the valve that's used to top up the central heating pressure has a leak. It,s not leaking from the pipe connections but from the spindal on the tap. It was fine last year, then before winter it leaked when you opened the tap, now its just plain leaking.

I will be able to replace the valve but am wondering if I will have to empty the system to do this. Below are my crude drawings and technical diagrams:

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• cartman44
• 28 Jan 2010
• 2

Here the colours are:
Yellow: Gas inlet
blue: mains in
red: DHW flow
Green: Central Heating return
Purple: Central heating flow
brown: problem valve

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• cartman44
• 28 Jan 2010
• 2

Untitled

• cartman44
• 28 Jan 2010
• 2

I can obviously shut off the mains water at the house stopcock and the stopcock on the boiler.

My question is with the other side of the valve being attached to the central heating flow, will the all the radiators dump their load if I disconnect the valve there????

Thanks

Mark

 

[sourcebranch]

Hi.
Normally the filling loop is between the cold water inlet and the ch return but if have come across them on the flow.
The filling loop will have two valves connected to the filling hose. one of them should be a non return valve. This will normally be slightly longer than the normal isolation valve. If the non return valve is on the heating side then there should not be a problem and you will only have to isolate your cold water. Be advised non return valves have been know to leak!!!! Shut off the valve and slowly undo the hose. Good luck

 

[cartman44]

There is another valve, looks like a standards isolation valve but where there would normally be a screw thread there is not, its just like a nut - would this be it?

If so its definately on the mains side of the faulty valve

There's no other valve I can see between the faulty valve and the flow pipe for the CH before the pipes disappear into the ceiling

What would be the best way to drain the system if I have to do that?

Thanks Mark

 

[sourcebranch]

The one with the nut on sounds as though it is the non return valve.

What is the make and model of boiler?
Is it upstairs or down?

 

[cartman44]

Hi there
iirc the boiler is a vokera 24se compact......... I'll check when I get home. It's downstairs and the CH flow pipes run straight into the ceiling above. Like I say there is no other valve after the faulty one on the boiler side...... Not one that I can see anyway.

Thanks for your help so far

mark

 

[Agile]

Although yours sounds old, the correct position for the double non return valve since 1999 has been on the mains water supply side.

If yours is fitted this way then the Ch has to be pressure reduced to zero and then a new valve can usually be fitted by an experienced persion using a quick snatch change. That has to be practiced but can usually be done without spilling more than about 1/2 litre.

One of my trainees practiced doing rad valve changes like that with two people using a wet and dry aquavac.

Tony