Ah, the common urinal, known in the British Army as the 'Gunners Barrel'... Possibly from the tradition of pissing down the muzzles of muskets to clean the caked on powder during battle when stopping to boil a can of water was too lengthy a process but not cleaning the muzzle was too dangerous. A clogged musket barrel will cause a misfire and the thing will explode in your face or project your ball about 3 feet downwards.

LTS