Loud banging in pipe when water is off?

[John D v2.0]

If the lever valve is your stop cock (should be a proper stopcock really with a drain valve after it) then put it directly after that. Ideally straight in line with the incoming pipe, with the pipe going to the rest of your stuff off to the side.
I had another thought, more of a theoretical one though, if it's stopping when your stop cock is off, you could add a pressure reducing valve just after the stop cock. You'd end up with slightly worse pressure and it would be complicated to set up, but in theory it would work.

 

[zenonithus]

Hey John, ok thanks I will look into that. So with the pressure reduction valve would that stop the hammering from below? Also what is the difference between lowering the pressure on the stop lever against having a pressure reducing valve?

So really trying to figure out what changed recently as to why I am getting hammering from the flat below into my pipes. The only thing they have changed below recently is getting a new washing machine. This is the main cause of the constant banging. If they fitted arrestors at the back of this washing machine would the banging stop?

Also someone suggested once my taps are reconnected and switched on they might spit out trapped air which could be a cause.

 

[John D v2.0]

So with the pressure reduction valve would that stop the hammering from below?

Yes, as long as the banging is caused by the pressure wave in pipe work after the vale, and the valve is set lower than the prevailing water pressure.

Also what is the difference between lowering the pressure on the stop lever against having a pressure reducing valve?

You can't lower pressure using a stop valve, you can only lower the flow rate. That would affect the dynamic pressure meaning terrible showers etc. A private should maintain pretty much the same flow rate. Think of it like a surge protector. However I'm not recommending that course of action as it's probably unnecessary and overly complex to set up.

The only thing they have changed below recently is getting a new washing machine. This is the main cause of the constant banging. If they fitted arrestors at the back of this washing machine would the banging stop?

It would stop banging caused by the washing machine and improve banging from other sources. Maybe the old washer had an old baggy supply pipe. Or maybe the old one shut off slower.

Also someone suggested once my taps are reconnected and switched on they might spit out trapped air which could be a cause.

Could be, maybe your taps are absorbing the shock and causing a brief flow in the rest of your pipes.

 

[zenonithus]

great, thanks for answering all that John. I think the next step is to get an arrestor fitted just above the lever valve. Really hope it sorts out the hammering. Also I need to fix the pipes securely somehow as they are just floating like that and can make the banging worse.