Water hammer from unvented cylinder

[dilalio]

New build

Says it all tbh.
Do you speak with any of your neighbours?
Any similar issues?

 

[Taconite5]

Says it all tbh.
Do you speak with any of your neighbours?
Any similar issues?

I know. The plumbers were morons. Taps were fitted with hot and cold wrong way in kitchen. Copper pipes bent with kinks in them.

Yeah but they are all slightly different. Like one similar house has their EV directly off the ICG - mines off a T. It’s hard to understand if it’s the same banging without going inside the house myself!!

 

[Johntheo5]

mines off a T. It’s hard to understand if it’s the same banging without going inside the house myself!!

There is nothing between that T (for the EV) and the cold water inlet to the UVC??.

If you open the outside tap which is fed directly from the mains instead of one of the balanced ones but in the same sequence that produces hammer does it have any effect?

 

[Taconite5]

There is nothing between that T (for the EV) and the cold water inlet to the UVC??.

If you open the outside tap which is fed directly from the mains instead of one of the balanced ones but in the same sequence that produces hammer does it have any effect?

So it comes out of the ICG, T with the EV and then straight into Cylinder inlet. I do wonder if the reason why I don't hear it is if I let the whole thing settle for a bit (and the boilers been heating water) - it's because the heat/pressure is building up in the pipe after the ICG - you can feel the pipe get warm, mostly up the T piece with the EV. If you then run a hot tap cold water then flows through into the cylinder feed cooling everything down and equalising everything again? Does that make sense?

Wouldn't opening the outside tap be the same as running the kitchen cold tap? They both come off the same feed downstairs before it goes into the ICG. I can try it!

Another brainwave....between the balanced cold and the main inlet is there a check valve on the ICG? Or is it just on the cylinder inlet port? Reason I ask if there is a valve and a tap closes there's no where for the pressure to go...just wondering if that also needs a shock arrestor.

 

[Taconite5]

There is nothing between that T (for the EV) and the cold water inlet to the UVC??.

If you open the outside tap which is fed directly from the mains instead of one of the balanced ones but in the same sequence that produces hammer does it have any effect?

I tried the kitchen tap method - didn't do anything!

 

[Taconite5]

Same problem here -

https://www.reddit.com/r/askaplumberUK/comments/1qu5ll2/cold_water_noise

Same cylinder, same multibloc, also a new build!

 

[Johntheo5]

So it comes out of the ICG, T with the EV and then straight into Cylinder inlet. I do wonder if the reason why I don't hear it is if I let the whole thing settle for a bit (and the boilers been heating water) - it's because the heat/pressure is building up in the pipe after the ICG - you can feel the pipe get warm, mostly up the T piece with the EV. If you then run a hot tap cold water then flows through into the cylinder feed cooling everything down and equalising everything again? Does that make sense?

Wouldn't opening the outside tap be the same as running the kitchen cold tap? They both come off the same feed downstairs before it goes into the ICG. I can try it!

Another brainwave....between the balanced cold and the main inlet is there a check valve on the ICG? Or is it just on the cylinder inlet port? Reason I ask if there is a valve and a tap closes there's no where for the pressure to go...just wondering if that also needs a shock arrestor.

OK, so its associated with the balanced cold only, (the kitchen tap is taken off the mains as you said)

There is a check valve (NRV) in the ICG as shown below, this means that the EV if teed off the ICG port is only seeing the UVC pressure and will rise when the cylinder has been heated, EVs are commonly sized to 10% of the UVCs volume so you will probably have a ~ 18L EV, if its precharge pressure is 3bar then, with the PRC set to 3bar, it will rise to 3.79bar after a full 180L reheat to 60C, the expanded vol of 2.97L will have to flow back through the connecting pipe to the EV so will certainly get warm/hot depending on where the bottom of the heating coil is positioned Your T off should behave exactly the same as the ICG internal check valve will work exactly the same way, I have seen installations that don't have a ICG, they have a 3bar PRV, then a check/NRV and then a T off to the EV.

The PRV will prevent the UVC EV acting as a shock arrestor as it will be closed at any pressure > 3.0bar so the pressure really has no where to go, thats why I suggest installing a arrestor at the PRV end or in the balanced cold.

 

[Taconite5]

OK, so its associated with the balanced cold only, (the kitchen tap is taken off the mains as you said)

There is a check valve (NRV) in the ICG as shown below, this means that the EV if teed off the ICG port is only seeing the UVC pressure and will rise when the cylinder has been heated, EVs are commonly sized to 10% of the UVCs volume so you will probably have a ~ 18L EV, if its precharge pressure is 3bar then, with the PRC set to 3bar, it will rise to 3.79bar after a full 180L reheat to 60C, the expanded vol of 2.97L will have to flow back through the connecting pipe to the EV so will certainly get warm/hot depending on where the bottom of the heating coil is positioned Your T off should behave exactly the same as the ICG internal check valve will work exactly the same way, I have seen installations that don't have a ICG, they have a 3bar PRV, then a check/NRV and then a T off to the EV.

The PRV will prevent the UVC EV acting as a shock arrestor as it will be closed at any pressure > 3.0bar so the pressure really has no where to go, thats why I suggest installing a arrestor at the PRV end or in the balanced cold.

Thanks.

But there’s no NRV between the inlet and the balanced cold port? I’m just trying to understand why the arrestor before the inlet had no effect (even trying to make it a bit quieter).