Picture shows how your tubes can look after twenty years. You see how ferrum and magnesium caused a serious block here at the water trough entry. This caused the water flow to slow down to 3 liters per minute. Not nearly fast enough!
The farmer fixed the problem by instaling new, 3 cm wide pipes, a big entry and a pressure pomp. Now he has a fast drinker with the required flow of 20 liters of water per minute. Great job!
So: check your drinkers! Especially with the summer coming up!