Water meters and monitoring
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Water meters are key in managing your farm's water usage. Costing around $350, water meters will help you spot leaks early,track consumption and are a valuable feature of any farm striving for sustainable water use.
Installing a water meter allows you to record actual water use and identify areas where water can be used more efficiently. This page provides information on the different types of meters and their use and installation, as well as regulatory requirements.
Types of water meter
Two main types of water meters are available to monitor shed water use: mechanical and electromagnetic. The cost and accuracy vary between these meters. Mechanical water meters are generally the cheapest upfront, however they need earlier replacement and have poorer accuracy than electromagnetic.
Mechanical water meters
Most mechanical meters have an impeller rotated by water passing through the meter. The amount of turns is translated to a volumetric reading. The meters are available in various sizes, and the pipes on either side of them must be full of water during measurement to ensure they are accurate.
Mechanical water meter.
Advantages
- Reliable and accurate measurement provided the meter is correctly installed.
- Relatively low initial cost compared to electromagnetic,
- In-line maintenance with a simple, efficient mechanism.
- Replacement for parts (e.g. impellers) is readily available.
Disadvantages
- Difficult to detect malfunction or human interference to meter while operating if operated with a data-logger.
- Prone to wear in silty water, potentially resulting in loss of accuracy.
- Some head loss characteristics.
Electromagnetic water meter
An electromagnetic meter consists of a section of pipe with a magnetic field around it. Electrodes determine flow based on how the water flow changes the electrical voltage.
This type of meter is produced in various standard sizes and flow capacities.
Electromagnetic water meter.
Advantages
- High degree of accuracy (+/- 0.15-2%) and consistent over the entire flow range.
- Wide flow range and no obstructions to flow.
- Robust with minimal routine maintenance required.
- No moving parts.
Disadvantages
- Power supply required.
- Electronic components are vulnerable to lightning damage.
Selecting a water meter
Irrigation New Zealand's Water Measurement 'Blue Tick' accredited operators are recommended to install water meters (which may be required by your regional council), and can provide advice on the most suitable option.
When deciding which water meter best suits your farm, consider the following questions:
Is there anything in your water that may affect the meter?
High silt loads, weed issues, sand, pumice, iron or manganese in source water can all affect the performance of a meter. Mechanical flow meters will wear out faster in silty or gritty conditions.
How accurate are water meters?
Selecting a meter with the manufacturer's stated and tested standards is essential if you require a specific data accuracy level. Ensure the meter has a maximum accuracy of five per cent. This means that readings are considered within or minus five per cent of the actual flow.
A meter will only be accurate if the manufacturer’s specifications are met, including flow profile, temperature, humidity, flow range and vibration.
Using and monitoring water meters
Meter location
Place the water meter in a convenient spot to read or attach a data logger or telemetry unit, which will send the data straight to a computer system.
Consider how the meter’s location will affect the data collected. For example, if you install a meter on the line of a slow-filling tank that gravity feeds, it will constantly show low values, and leaks will be hard to detect. If you put the meter (with telemetry) on the outlet of the water tank, it will be more sensitive to changes in flow. Low leaks can then be detected when the flow is seen outside normal animal drinking hours.
Monitoring water meters
Read meters at the same time and day regularly to ensure readings are consistent. Readings can be recorded on DairyNZ's Tracking Water Use form.
At least once a month, read the meter late in the evening and again early the following day to check for small or unnoticed leaks.
Assigning meter-reading responsibility to one person makes it part of a routine and reduces the chance of it being forgotten.
Tracking trends
Record meter readings regularly to track seasonal and yearly farm water use. The industry estimates that typical water use for milking cows is about 140 litres/day (70L for drinking and 70L in the farm dairy).
Weather conditions and feed will affect stock water intake. If overall water use on the farm regularly exceeds 140L/day, it’s worth having a closer look for possible water losses or inefficiencies.
Telemetry monitoring offers continuous electronic monitoring of your water use. Some councils now require this as a condition of consent.
Detecting water leaks
An alert system can tell you if water is flowing when it shouldn’t, allowing quick detection of leaks and speedy repairs. Assign a specific person to monitor the alert devices.
An alert system can be set up using the following methods:
- A pressure gauge on a line feeding water to the farm, that registers lower than normal, is a likely sign water is being lost somewhere in the system.
- If a storage tank and pump provide water down the farm, a pilot light on the pump can serve as a visual alert that the pump is on. If the pump is running when it shouldn’t, there's likely a leak, and you should look for the cause.
- A standard spotlight of an LED variety that is visible from a distance, and also in daylight is worth the small extra cost.
- The ‘click, click’ sound of an in-line dispensing system can alert you that water is running.
- Unexpected fluctuations or records that never return to zero on meter readings may also indicate leaks.
Isolation valves to reduce impact of leaks
The correct number and placement of isolation valves can ease finding and fixing leaks, and shutting off water in an area to assist in repair. They can also be used to turn off water in areas not always in use, such as the calf shed. Mark isolation valves on your farm map so they can be found if the system needs to be modified.
Water metering regulations
Consented water that takes over 5 litres per second or more must be measured and reported to regional councils. The water metering regulations were amended in 2020 and now require water takes to be measured every 15 minutes and reported to regional councils daily, which essentially means a telemetered system. If you are upgrading your system or putting in a new system it will need to be able to comply with the reporting requirements.
See water metering regulations for further information.