While water supply has been on the back of many people’s minds, summertime and warmer weather matching up with cows and ewes hitting peak milk yields will cause a dramatic increase in the volume of water that animals consume.

Ensuring a sufficient amount of clean, fresh water is available to stock is essential.

Two major factors will dictate if the current water system in place is fit for purpose or if modifications are required – the trough size and the flow rate of pipes.

Peak demand for water occurs at peak grazing time which, for dairy herds, is after each milking. Teagasc suggests that up to 50% of the daily water intake of a cow occurs in the three hours after each milking.

It is recommended that 10% of the herd is able to drink at the one time, with each cow requiring 450mm of trough space.

Typically, rectangular troughs have a greater perimeter-water capacity ratio compared to round or elliptical troughs.

A recommendation by Teagasc is for a trough capacity of nine litres/two gallons per cow, equating to a 900-litre or 300-gallon trough for a 150-cow herd.

To encourage drinking, cows should never be more than 250m from a trough, with troughs placed in the centre of paddocks for this reason and to encourage even graze-outs.

Troughs should be situated on an elevated, dry site, and due to the high traffic around them, it is preferential to have a hardcore/gravel base around troughs.

Not only will this prevent the area around troughs from becoming poached and waterlogged, but it will also prevent troughs from becoming unbalanced due to sinking into the top soil.

For other livestock types, a good rule of thumb is that for every 100kg of liveweight, an animal will drink approximately 15 litres of water per day.

For lactating ewes with lambs, this will result in a water intake of nine to 10 litres. For drystock, a reduced rate of seven litres/LU can be used to calculate trough requirements, eg 25 suckler cows and calves= 25 cows @ 1.0LU + 25 calves @ 0.4LU x litres =245 litres/ 53.89 gallons.

Pipe diameter

A far more common issue with water supply on farms is inadequate pipe diameter resulting in poor flow capacity. As dairy herd sizes have increased, so too have milking platforms and the distance water must be piped.

The further the distance water has to travel through a pipe, the greater the loss of pressure due to friction between the water and the internal pipe surface.

For example, at a flow rate of 3m3 per hour (50 litre/min or 11 gallon/min) with a 32mm (1¼ inch) pipe, the pressure is reduced by 4.83PSI for every 100 metres of pipe.

To determine flow rate in a trough, lift the ball cock, empty a fixed amount (eg 50 litres) and time how long it takes the trough to refill. A simple calculation will show the litres per minute flow rate.

Where flow rate is inadequate, a larger diameter pipe can be installed. For herds with less than 150 cows, pipe diameter should be a minimum of 25mm (one inch), and for herds of 150 to 300 cows this should rise to 32mm minimum (1 ¼ inches).

A 40mm (1 ½ inch) pipe should be installed for herds greater than 300 cows.

Pipes carrying water with a high iron concentration can also have a buildup of iron causing a reduced flow rate, especially where the pressure per square inch (PSI) is lower than ideal. Where pipes are checked and found to have iron buildups, the likelihood is that they will have to be replaced.