While the water trough in your paddock is just a very large drinking bowl, it comes with a lot of extra bits. Most of these are to control the flow of water into the trough and thus keep water always available for your animals while avoiding overflow and water loss.
The trough itself can come in a wide range of shapes, sizes and materials. Your choice will be determined by the number and kind of stock you have, and the location of the trough in the paddock. The nature of your water supply (gravity feed from tanks, or pumped under pressure) may also affect what kind of trough you choose to buy. Most farm supply firms will be able to help you make a sensible decision. For online advice on design, reticulation systems, tanks, troughs, pumps, and fittings, have a look at the Farmlands Rural Pipelines site.
The major components of the control system in your water trough are: the trough valve or ballcock (like the one in your toilet); a stop valve (also known as an isolating valve); and a check valve or backflow protection valve. You will probably also want a valve protector to prevent stock from damaging the water inlet valve.
The ballcock or trough valve is the bit that prevents overflow. The traditional version is a float (the ball) on a lever attached to a valve on the inlet pipe. When the ball is floating near the top of the trough, the lever holds the inlet valve closed and no water enters the trough. As the level drops, the ball moves down with the water, the lever tilts and allows the inlet valve to open. Water flows in until the ball again floats high enough that the lever pushes the valve shut. There are many variations on the theme, depending on whether the water enters the trough from the top, the side, or the bottom, and on the operating water pressure in the system (which can range from 0.2 to about 12 bar). Trough valves can fail, so regular checking and maintenance is needed to make sure they keep working properly. For a video on how to install one type of valve used in New Zealand, see here.
A stop valve allows you to isolate one trough so you can work on it, while keeping all the other troughs on your property functioning normally. Because the valve is on the outside of the trough, it needs to be housed in a stock-proof box to prevent damage by nosy animals. Again, a variety of types are available, and the one you choose will depend on the size of your system, operating pressures, and local weather conditions.
A backflow prevention or check valve is particularly important if your house water supply is linked to the farm supply, and your house is below the level of the highest trough. The prospect of saliva-laden, algae-filled water trickling from your kitchen tap is nasty, and a check valve acts like the valves in a vein to stop backflow through the system. The valve will also remove any chance of water siphoning out of upper troughs to ones at a lower level.
Water troughs need to be hygienic to support good animal health, and a total cleanout is recommended about every three months (that’s where the isolating valves come in handy). Troughs don’t normally have drains or outlet valves, so the standard technique is to bail out the contents, scrub the walls and scoop out the residue. If you can, choose a warm sunny day and leave the tank empty for a few hours to help kill off the algae before refilling. If you have clean water always available, your animals will drink more (and cows will produce more milk, in compensation for your efforts).
It’s also advisable to make sure your troughs are installed on a solid layer of gravel, so the area around the trough stays as dry as possible and provides safe footing for your stock.
With good installation and regular maintenance, your troughs should provide a reliable, clean water supply for your stock, with minimum water wastage.