A lot a fanciers are unaware that many vitamins and medicines loose their efficacy over time when diluted in water especially on warm days.
This leaves a Fancier with an apparent dilemma when administrating medicines or vitamins as when inspecting the water drinker in the evening the drinking water looks clean enough and it seems faster and cheaper to just top up the drinker. This is bad practice as the vitamins or medicines having been in the water all day are probably ineffective and if you top up the drinker with fresh water and medicines you are effectively diluting the new medicine. So to effectively administer medicines and vitamins in water you should preferably provide fresh water and dosages twice per day.
To reduce cost of treatments when doing the evening round you can firstly empty ALL the drinkers in each section and then produce a fresh batch in one drinker.
This single fresh drinker is moved to each section in turn having left the single drinker in each section for say 15 minutes and topping up with fresh treatment if necessary between movement between sections. This drinker can be removed at night from the last section ensuring the pigeons are ready to drink a fresh supply of treated water the produced and supplied the next morning.