Airlock in Hot feed pipes?

[kristeva]

Hi all

I have problem with what I think could be trapped air in the pipe work of the hot feed at my mum’s house. About 10 seconds after turning on any of the hot feeds in the house a dreadful, loud groaning noise occurs in the pipe work, along with a fair amount of shaking / hammer I reckon. It’s coming from the upper part of the house – (hot tank on first floor and above). The water runs fine as normal, and the noise can only be avoided if the tap is opened a quarter turn.

The system is gravity fed



I closed the valve gate directly beneath the main tank and tried draining the hot tank but to no effect. I’m not entirely sure I drained it completely as it seemed to take ages to empty. (I understand valve gates don’t completely shut off the water?). Interestingly the noise occurred when I opened the valve gate but only for a few seconds. So I’m wondering is this an airlock of some sort – should I try shooting cold mains up the pipe work? Or should I get someone in to take a proper look?

The only cause we can think of is it started to occur after my mum had switched off the hot water completely during that warm spell we had the beginning of summer. Whether this has any bearing I don’t know.

Any advice appreciated.

 

[Plumbstar Tom]

could it be the fill valve to the cold water tank? That will be on mains pressure and can be noisy when they get old

 

[plumben]

As above it could be the cwsc in the loft that feeds the hot water tank, as when you remove water from the cylinder by a hot tap the cold water level will drop and open the ball valve, if the tap only opens a small amount then only a slight amount of water will be needed to refill and these valves usually cause water hammer when the washer gets old

 

[gassafe]

Yeah sounds like a new float valve needed...

 

[PlumbBobBob]

agree with everyone else ball valve on cold water cistern needs replacing

 

[Unregistered]

Thanks all for the responses.

So you all think it's an issue with the ball valve feed into the main cold water tank in my loft? That's strange because this was replaced only a year or so ago. I'm just curious, why would the noise not occur when I run the cold taps? (apart from the direct feed in the kitchen).

Thanks

 

[Rckape]

It's usual now to have all taps fed from the cold main rather than the tank as shown in your diagram.

This would not affect the ball valve. I agree with everyone else. Have you done any work on the system or has the water board done any work in the street recently? It could be something as simple as a bit of grit in the valve seating. I have also known cheap import valves fail after such a short time.

I'd replace it with a pegler or similar.

 

[kristeva]

It's usual now to have all taps fed from the cold main rather than the tank as shown in your diagram.

This would not affect the ball valve. I agree with everyone else. Have you done any work on the system or has the water board done any work in the street recently? It could be something as simple as a bit of grit in the valve seating. I have also known cheap import valves fail after such a short time.

I'd replace it with a pegler or similar.

The only work carried out was to replace the ball valve feed to the main tank in the loft. This was carried out by a plumber maybe a year ago. Maybe he used a cheap part.