Of all the things to run out of, water is the last thing you want to be short of. Cattle need ad-lib access to fresh, clean water at all times.
This requirement is exacerbated in hot weather because cows sweat more to keep cool and thus drink more water to prevent dehydration. Typical water intakes during the real hot days can be up to 130l/cow/day.
About half of the total water intake is drunk in the first hour after milking. So if a cow is drinking 120l of water in the day, 30l is drunk an hour after morning and evening milking. This puts a big strain on water supply after milking as not only are the cows drinking more then, but water is required in the dairy to wash the milking plant and the parlour and yards.
On-farm measurement by Teagasc shows that on average 1.28l of water per litre of milk produced are used for washing down yards.
For a typical 100-cow farm, this is about 1,000l of water used for washing down after each milking. A 10-unit parlour should use 380l of water in a rinse/wash/rinse cycle.
So, in the first hour after milking, a 100-cow herd will use 4,380l of water which is a requirement of 73l per minute. If cows were only drinking 60l/cow/day, the demand would be 48l/min in the first hour after milking.
Not only is the demand up in this weather, but in many wells the supply is down. This is because there is less movement of water through the soil and into the well so pumps are working harder to get water to the surface. Where the demand for water cannot be met, water troughs are running empty and the pressure in pipes is reduced.
Some tips
The following tips can help to overcome problems in the short term.
Because there is a huge demand at milking times, a water reservoir is essential in most situations. In the example above, a 5,000l water storage tank from which water was pumped could supply all the water needed for an hour after milking. This water storage tank should be fed from a well or the mains and the outlet from the plate cooler should be fed into this too. While a reservoir mightn’t reduce pressure on a well, it will maintain supply to water troughs during the critical time after milking.While pipe size to water troughs is more important than trough size, the size of the ballcock has a massive bearing on flow rate. No matter how big the pipe to the trough is, it must pass through the ballcock. If cows drink 30l in the first hour after milking, then 100 cows will drink 3,000l in the first hour. If there is 640l (140gal) in the water trough to start with, 2,360l will have to flow into the trough in the first hour, which is 39l/min. Most water troughs in the country have a 0.5in brass ballcock with high-pressure jets. The greatest amount of water that can flow through these is 8l/min, well short of what is required on most farms. Replacing these jets with low-pressure jets will increase the flow rate to 42l/min. The low-pressure ballcocks have a bulkier head and can be bought in most farm stores. Where trough size or flow rate is limiting, including extra water troughs in the collecting yard or as cows walk away from the parlour will take the edge off them before they get back to the field. Adding in a loop will double the flow rate to the troughs. Temporary loops can be added in by laying pipes over ground and across roadways to connect end of lines.
Of all the things to run out of, water is the last thing you want to be short of. Cattle need ad-lib access to fresh, clean water at all times.
This requirement is exacerbated in hot weather because cows sweat more to keep cool and thus drink more water to prevent dehydration. Typical water intakes during the real hot days can be up to 130l/cow/day.
About half of the total water intake is drunk in the first hour after milking. So if a cow is drinking 120l of water in the day, 30l is drunk an hour after morning and evening milking. This puts a big strain on water supply after milking as not only are the cows drinking more then, but water is required in the dairy to wash the milking plant and the parlour and yards.
On-farm measurement by Teagasc shows that on average 1.28l of water per litre of milk produced are used for washing down yards.
For a typical 100-cow farm, this is about 1,000l of water used for washing down after each milking. A 10-unit parlour should use 380l of water in a rinse/wash/rinse cycle.
So, in the first hour after milking, a 100-cow herd will use 4,380l of water which is a requirement of 73l per minute. If cows were only drinking 60l/cow/day, the demand would be 48l/min in the first hour after milking.
Not only is the demand up in this weather, but in many wells the supply is down. This is because there is less movement of water through the soil and into the well so pumps are working harder to get water to the surface. Where the demand for water cannot be met, water troughs are running empty and the pressure in pipes is reduced.
Some tips
The following tips can help to overcome problems in the short term.
Because there is a huge demand at milking times, a water reservoir is essential in most situations. In the example above, a 5,000l water storage tank from which water was pumped could supply all the water needed for an hour after milking. This water storage tank should be fed from a well or the mains and the outlet from the plate cooler should be fed into this too. While a reservoir mightn’t reduce pressure on a well, it will maintain supply to water troughs during the critical time after milking.While pipe size to water troughs is more important than trough size, the size of the ballcock has a massive bearing on flow rate. No matter how big the pipe to the trough is, it must pass through the ballcock. If cows drink 30l in the first hour after milking, then 100 cows will drink 3,000l in the first hour. If there is 640l (140gal) in the water trough to start with, 2,360l will have to flow into the trough in the first hour, which is 39l/min. Most water troughs in the country have a 0.5in brass ballcock with high-pressure jets. The greatest amount of water that can flow through these is 8l/min, well short of what is required on most farms. Replacing these jets with low-pressure jets will increase the flow rate to 42l/min. The low-pressure ballcocks have a bulkier head and can be bought in most farm stores. Where trough size or flow rate is limiting, including extra water troughs in the collecting yard or as cows walk away from the parlour will take the edge off them before they get back to the field. Adding in a loop will double the flow rate to the troughs. Temporary loops can be added in by laying pipes over ground and across roadways to connect end of lines. 
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