Water hammer from part 2 ballvalve

[Timmyturtle]

Went to look at an old ladies overflow

Ballvalve in main loft tank was not shutting off properly

The arm had a large iron nut(like a ch pump extender)with the arm through the middle acting as a weight

when i took the nut off it started water hammering,obviously why someone had put it there

Ive never had a part 2 do this

Any suggestions how to stop it?

 

[bengasman]

Put the weight back on. Not joking, it acts as an inertial dampener something creates a wave in the tank which opens the valve quickly and closes it just as quickly causing the hammer