Little drinking or urinating

Cookie (my 7 year old staffy x) has never drunk vast amounts, however recently he has pretty much stopped drinking and urinating.
He has burns dry food with water (about 50ml at most) on and a small amount of wet to make like a thick gravy, raw for dinner (usually a chicken leg) and then same as breakfast for tea. He also has treats for training and a charcoal boneo or similar before bed.
He used to drink a few bowls full in summer but now I rearly see him drinking anything and the water in his bowl doesn't seem to be going any where. The vet has checked him over and just said he seems fine and to keep a close eye, as he has never been big on drinking lots.
His urine has always been quite strong but now he doesn't even seem to urinate much, he will usually go about 3pm and before bed, even though I take him out much more often, and he will still sent mark on walks. This can't be healthy for him but how do I get him to drink more.
I am tempted to just add more to his food but that's not really teaching him to drink is it?
Please help, this has been driving me crazy and no one seems to have any advice on how to get him to drink more or what it could be.

Well we have 2 adult Boxers & 2 cats who all drink out of the same bowl, it holds 2 litres. Between them on average day the bowl is still nearly full at the end of the day & one of the dogs has renal disease so you would think she should be guzzling water. She does at times to be fair when the renal disease is out of control but on average not much

Our dogs go out to wee at breakfast, 4-ish & bedtime. Our boy doesnt scent mark, he does his wee at home in garden all at once which is very convenient

If hes been checked out by the vet & ok, i wouldnt worry. Hes obviously getting enough to do him

Thank you for your reply Velvetboxers, it just worries me that he doesn't seem to drink anything but if your 4 don't drink much either maybe I am just being overly cautious. I've seen friends dogs empty their water bowls in one go! Cookie at most dips his tongue and walks off again.
I'll just keep monitoring him for now.
Thanks again