Water leak

Hi all

An unusual one. I have a ten plate astra.1.4

I have had a water leak for a number of years. Car has gone in to various garages on a number of times. On all occasions bar the last time nothing can be found. But the last time they said it was the valve at the side of the block. It was replaced but still can be found..

Origionly the leak was a centemter evey 6 weeks then gradually got worse. Now i am putting in about half a pint a week.

I do not have the following..
Milky residue...

Water leak