I have now topped up the water with about half a litre twice in two weeks but cannot for the life of me find where it is being lost. Can anyone advise me where to look?where is it going?????

 

what engine?
what year?

it's either being sucked into the head or it's pissing out the heater matrix

get one of them sniff tests done for the header tank at a rad specialist or take it to the local mot place to see the reading from the exhaust

 

Hi dojj. Just driven car this morning and noticed water pissing down. I could not believe where it was coming from. A pinhole has been created under the header tank by rubbing on its bracket and when the car gets to pressure it pisses out. Not noticed it before as has been raining where i am. DOH!!!! Never seen this before, has anyone else. Thanks for your reply though. Will keep them in mind

 

I had a brand new top hose on a mini years ago, that had a pinhole in it, only leaked when warm/hot.
tabetha