Tap water in pubs - charges

I found out why I was asked about this in the first place. Turns out it was at a junior cert disco - they were charging €2.50 for water and blocked the taps in the bathrooms. Nice.

blocking the taps in the bathrooms used to be a fairly regular occurance in some of the seedier places I used frequent in my youth. I never did understand the point of it as switching off the water meant the toilets couldnt be flushed either and they would end up in a terrible state - in my inebriated youthful state I used to think that they were only shooting themselves in the foot cos theyd have to pay some unfortunate staff member to clean the toilets out.

Now I understand!! It lets them charge a fortune for water!!!

I used to think that blocking the taps was because those on "E" have to drink alot of water and by doing this would cut down on the use of the drug.
Would this be the motivation in the case of a junior cert disco - I hope not.