Heating Bangs when switching off.

[Paul Cooksn]

Are these bypass valves or air bleed valves. They are a few meters from the boiler.

 

[Last Plumber]

Sorry was checking the wrong one. You are right, no resistance when on. I held it open, turned off and no bang. Can still hear water going into header tank? Does this mean the valve is faulty.

Cheers

It can be a faulty valve yes but in your case I would suspect that the lack of a system bypass is causing the valve to slam shut as the pressure increases on closing. (valve damage may have occurred as a result of not having a bypass).

My advice:-
Install a system bypass (22mm Auto) and see if it stops the bang. If not replace the valve. You need the bypass anyway.

 

[ShaunCorbs]

Agree with the above but as your draining down I would replace the valves at the same time, if you can afford the slightly extra cost

 

[Last Plumber]

Agree with the above but as your draining down I would replace the valves at the same time, if you can afford the slightly extra cost

Good point!
Do that!
Replace valve and install a Bypass.

 

[ShaunCorbs]

Are these bypass valves or air bleed valves. They are a few meters from the boiler.



View attachment 31464

Looks like auto air vents

 

[Last Plumber]

Bit dark but I agree wi Shaun

 

[Paul Cooksn]

Great help guys thanks very much. One more question where should I fit the bypass valve. Close to the boiler or in the airing cupboard.

Cheers.

 

[Paul Cooksn]

Bit dark but I agree wi Shaun

They were hissing air when the system was refilling so guess they are air vents.

 

[ShaunCorbs]

They were hissing air when the system was refilling so guess they are air vents.

Airing cupboard

I would fit it in between the port valve tees and straight onto the return

 

[stratplus]

Airing cupboard

I would fit it in between the port valve tees and straight onto the return

Yes it needs a bypass.
If you try holding the valve open whils someone turns heating off you’ll see if it stops the bang

Wouldn’t the rad in the hall and heated towel rail act as a bypass. Neither of these have trv’s.
So removing that landing rad shouldn’t have made a difference. He also joined the pipes from the rad he removed and it was still banging.

 

[ShaunCorbs]

Wouldn’t the rad in the hall and heated towel rail act as a bypass. Neither of these have trv’s.
So removing that landing rad shouldn’t have made a difference. He also joined the pipes from the rad he removed and it was still banging.

If these are piped in before any port valves yes they would

 

[Last Plumber]

Wouldn’t the rad in the hall and heated towel rail act as a bypass. Neither of these have trv’s.
So removing that landing rad shouldn’t have made a difference. He also joined the pipes from the rad he removed and it was still banging.

Not if they’re after the valve and they most likely are.
The bypass needs to be before the valve for when the valve shuts!

 

[Paul Cooksn]

Not if they’re after the valve and they most likely are.
The bypass needs to be before the valve for when the valve shuts!

Hi

I had a plumber attend yesterday and the valve was faulty, when taken off you could hear it making a grinding noise. He replaced the valve and the banging stopped but did say it probably needs a bypass valve fitting between the pump and valves then into the return. After a few hours the banging returned but it was much quieter. The plumber said the new valve is much stronger than the old one.

The bypass is being fitted Thursday so I will let you know what happens.

Cheers for all your advice.

Regards.

Paul.

 

[WYEO54]

Hi Paul
I would suggest that you check that the zone valves are actually positioned correctly for the differential pressure being created by the pump. The type of sound you have described indicates to me that a zone valve is slamming back when closing - this happens when a valve is positioned the wrong way to the flow - but looking at the photo they seem good to me but obviously I cant see the whole system layout design - so its difficult to be sure whats going on?
Best of luck getting it sorted... Bill

 

[Paul Cooksn]

Hi All,

I had the bypass fitted but there is still a slight bang when turning off. It still pushes water into the header tank as well. I also had fitted a new pump as the old one was nearly blocked. I have fitted a magnaclean on the return to the boiler and you wouldn't believe what muck came out of it in 24 hours.

Should I just put the radiator back.

Cheers.

 

[ShaunCorbs]

I would drain down and wack some x800 in the system for a week then drain it down again and fresh inhb

 

[Paul Cooksn]

I already did flush and the water ran clean. I opened all the bleed valves to get all the water out. The pump was old, dated year 2000 so it needed replacing anyway.

 

[Paul Cooksn]

Just updating again on this. I refitted the radiator and now the heating Bangs even more. Really am at a loss. Anybody with any further ideas.

 

[Frog67]

The fact that you have water flowing out the vent pipe when the system shuts down indicates you still have a fault, probably a blockage somewhere near the expansion pipe. You could try turning the speed on the pump down to its minimum to see if the noise reduces. Another thing to try would be to remove the rad again, empty it, refit, turn on the valves but don't bleed it. (it should act as an expansion vessel).
One thing i noticed looking at the pictures is the vent from the boiler looks like its running horizontal along the ceiling, so it may be possible that the system has an air lock.

 

[Frog67]

Forgot to say, that as you mentioned the amount of muck in the magnet suggests that the system needs a good clean.