Check Valves - Single & Double

D

DGS

Can somebody please explain the difference between a single and a double check valve. I have a valve in my central heating system that has failed and allows some radiators to become warm when the boiler is in hot water mode only. The valve that is fitted does not have any identification markings at all - any information would be gratefully received.
 
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That sounds like a diverter valve problem. Is it 2 port or 3 port? What make? and it might be just a motor.
 
D

DGS

Not that sophisticated I'm afraid - no motor, no ports - just an in line valve within the 15 mm pipework leading from the 22mm boiler outlet (not the 22mm connected to the pump). The valve has a triangle marked upon it (assume the point indicates flow direction?).
 
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check valves come in various sizes and designs. Sounds as though you have an 'inline check valve'. Some have a single valve seat whereas some may have two valve seats and they will be a little longer. The simplest form is those with a spring loaded ball (or two springs and two balls if double) allowing water in your case to flow in one direction only.
:rolleyes: :rolleyes: :rolleyes:
 
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D

DGS

Thanks - are there any regs that cover the type that should be fitted or any advantages to fitting a double as opposed to a single? I believe the one I have is a single - approx 3cms in length (thread to thread).
 
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DOuble check valves are not used in heating system pipes at all, only tap water. Need to know more about the layout to know for sure what this valve is - is it connected to the cylinder via a wire ? Does it have a handle on it?
 
D

DGS

No handle and no electrical connection and is located in the pipework less than a metre away from the boiler. Only visible "control" appears to be a bleed screw on the side.
 
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The check valve prevents contamination by preventing back flow and the chances of two valves failing are slim.
I came across a heating system where the hot water went along the heating pipes in a reverse direction and the problem was solved by fitting a single check valve and I assume your is fitted for the same reason.
:rolleyes: :rolleyes: :rolleyes:
 
D

DGS

Thanks for all the information - just the matter of replacing the valve then!
 
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You said 3 cms thread to thread, the one I fitted was more like 3 in and was 15mm compression fitting each side. About £5 from Wickes.
:rolleyes: :rolleyes: :rolleyes:
 

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