The five gallon bucket I used lasts about a week with the 8 chickens we have in that coop (longer on cooler days). When it runs low it's filled with a hose so no dragging a full bucket around.
Gail
Bought four nipples like these on ebay:
https://www.backyardchickens.com/forum/viewtopic.php?id=259012
Took a five gallon bucket, drilled four holes in the bottom, added the nipples, built a small stand attached to the coop, placed the bucket in this, adjusting the height of the bucket upwards...