Water hammer

[Taconite5]

Not sure what you mean by the above, its the air end pressure you are checking and setting so losing the water side pressure is correct and the only proper way to check it, what pressure have you set it to with the water side disconnected?.

Hi can you help me make sense of this...

I've fitted a pressure gauge to my system. It reads 4.5Bar initially, but if I open and close the kitchen tap rapidly it goes up to 8bar! It stays there even if I open the kitchen tap fully or close the water meter and run the kitchen tap empty. It only goes down if I run the dishwasher or close the ball valve and loosen the Y piece. I don't get why the pressure doesn't drop down again.....

The red X marks the location of the water hammer, if you open and close the "other taps in house" - is this because of the 8 bar surge?

What do I set the hammer arrestor to?

Does it need another hammer arrestor before the ICG?

 

[Johntheo5]

Looks like there may be another NRV just before the PG.

Just open the outdoor tap and the kitchen tap fully but slowly and note the pressure, it should fall, even if only by a small amount, then shut both taps very slowly and ensure the pressure returns to normal.

I would install a 2L EV precharged to 3.5bar in the place of the 0.16L arrestor, the 2L will accomodate 0.42L (water) if the shock then does reach 8bar which hopefully it now will not if this capacity EV is installed, the 0.16L will only accomodate 0.1L, 10ml, under the same conditions or still only 0.13L, 13ml, if precharged to 4.5bar.

 

[Taconite5]

Looks like there may be another NRV just before the PG.

Just open the outdoor tap and the kitchen tap fully but slowly and note the pressure, it should fall, even if only by a small amount, then shut both taps very slowly and ensure the pressure returns to normal.

I would install a 2L EV precharged to 3.5bar in the place of the 0.16L arrestor, the 2L will accomodate 0.42L (water) if the shock then does reach 8bar which hopefully it now will not if this capacity EV is installed, the 0.16L will only accomodate 0.1L, 10ml, under the same conditions or still only 0.13L, 13ml, if precharged to 4.5bar.

Hi thanks for checking.

I think you’re right that ball valve has a check valve in it!! Missed that!

This that hammer arrestor is under the sink - you still think it needs a 2L vessel?

 

[Johntheo5]

Yes, I would try that, it won't cost the earth.

 

[Taconite5]

Yes, I would try that, it won't cost the earth.

Ok. Just need to do some rerouting of piping.

I only asked because putting it before the ICG would have been easier as it’s in a cupboard upstairs - more room!

 

[Johntheo5]

Try that then, why not.

 

[Taconite5]

Try that then, why not.

Thanks! Fixed it! Hammer arrestor on the inlet before the ICG. Must be because of the PRV stepping it down from 4 bar to 3 bar was knocking it.

 

[Johntheo5]

What capacity EV (arrestor) and precharge pressure??

 

[Taconite5]

What capacity EV (arrestor) and precharge pressure??

It was just a tiny one 0.16L I had lying around just to test it out. It’s charged to 3.5bar.

If it reduces the noise I’m on the right track when will order a bigger one.

I put a gauge on it before the inlet - What was happening it was bouncing from 3-4bar in a sharp spike when a tap closed.