properly stuck on water noise

[still learning]

ok guys, brief background.
we have fitted a bathroom, new heat only boiler and few rads.
it was pumped heat gravity hot and we converted it to fully pumped y plan.


all works fine but we have a whooshing running water sound when on hot water only.
the f&e is in the loft, cylinder in a/c, pump on ground floor 3 meters from the new glow worm heat only.
I have re routed the combined f&e pipe from the cylinder where is was connected and now teed it onto the flow pipe between the boiler and pump hoping it may help… it didn't tho.


on heating and hot all is fine, as is heating only but when on hot water only this sound of glugging is in the pump, pipes down to pump and even gurgling in the cylinder to the point you'd assume there was no coil but there is .
its not primatic
I have checked all pipework apart from 2 meters under a fitted wardrobe for an anti gravity valve and no luck.


ive fitted an air vent to cylinder flow and got a bucket of water out, all rads bled to buggery and still this bloody noise.
customer owes me £3,500 for what we did and wont pay until this noise is gone.
I am at your mercy on this one guys.

 

[ShaunCorbs]

have you fitted a valve to the return of the cylinder as it could be flowing to fast round the coil

 

[Gasmk1]

i had a noise from coil on megaflo once and it was flowing round too fast causing it to vibrate worth a try fitting a valve or turn pump speed down on hot water only see if it stops then you know what the problem is

 

[jtsplumbing]

Did you replace the cylinder or just re-pipe ? much bigger coil inside gravity cylinder not really suitable for fully pumped system

 

[macackau]

Did you replace the cylinder or just re-pipe ? much bigger coil inside gravity cylinder not really suitable for fully pumped system

Yep. They sometimes have a sticker on saying only for Gravity use