I started this thread so I thought it best to let you all know how it
is progressing.

The boat in question is now out of the water and the insurance assessor
has completed his survey and estimated damage in excess of 12000 euros.
After listening to the advice on this NG I was worried the insurance
company would not pay out as my friend does not have a vented loop
fitted and yes the toilet manual valve was left open by the last user.

My friend received a phone call to say the insurance company would not
pay out in respect of this claim, expecting them to quote vented
loops...etc, but no! they said they would not pay out this claim
because in the small print of the policy it apparrantly states that
'boats must be lifted out for the winter by the 3rd November'. On
checking the policy my friend was horrified to find out he was not
covered.

Anyway to cut a long story short, the greek insurance company has
agreed to pay out in 'Good Faith' after a lot of pressure from the
Marina owner, but as you can guess the first item to be purchased will
be a Vented Loop!

Thanks to all