When AND ONLY when toilet is flushed there is a horrendous loud vibrating/hammering noise.This can last for quite some time and the only way we have found to stop it, is to turn on both cold water taps in the bathroom.

HELP--- SOLUTION PLEASE.

What you hear is the washer vibrating sgainst the ballcock seat. The reason it stops when you turn the water on is that you have lowered the pressure by opening a valve. You can go at this two ways. (1) you can lower the pressure by turning the angle stop located below the tank until the noise stops or, (2) you can shut off the stop and remove the three screws on top and cup your hand over the top and just crack the stop enough to flush out any trash that may be in there. After you do that pull the washer out of its holder and flip it over in its holder and reinstall the top and float. One of the two should do the trick. If not click on back and we will go to plan B. Good luck TOM

Hia Tom. Option 2 did the trick yesterday.Great.BUT today the noise problem has returned albeit its no where as bad as before.]Should I repeat the process?? Or something else. PLUS there is now a small leak coming from the joint--L shaped--directly adjoing the tank.

Yes, Pull and reseat the washer. Press it down tight in the stem. If it still vibrates then you have a faulty ball cock and it should be replaced. Please explain the leak you have. Is it the supply under the tank? Regards, Tom

The leak---light dripping,yes is coming from under the tank,where the water inlet pipe meets the tank at an L shaped joint.
I ll try the washer again later THANKS VERY MUCH

Snug up the nut connecting the supply to the ball cock and see if that doesn't stop the leak. Tom

Hia Tom.Changed the diaphragm washer and hammering STOPPED.WONDERFUL.
Tried snugging the nut but in doing so the ball cock inside moves about.Replaced washer in nut too BUT still got the leak.