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Performing a Field Test for Livestock Water Quality

Updated November 07, 2023
Professional headshot of Robin Salverson

Robin Salverson

SDSU Extension Cow/Calf Field Specialist

Myths About Water Quality

Cattle drinking from a stock pond with two geese resting on the water.
The presence of waterfowl in a livestock water source does not necessarily mean that the water quality is acceptable . Courtesy: Canva

A visual observation of livestock water ponds is not an accurate measurement of water quality. Some common misconceptions when determining water quality include the following.

  • Clear water is good water. Through years of testing, more samples that appear clear tested poorly than samples that appear murky. Why? The quality is so poor nothing else wants to live in it.
  • If waterfowl are on the pond, this means good water. This observation is not foolproof. Poor quality water has been noted on ponds with waterfowl.
  • If it is spring fed, it is good. This is also an incorrect statement.

Conducting a Quick Test

The only way to confirm water quality is by completing a “quick test,” either in the field or in a laboratory. The “quick test” is performed with a handheld electro-conductivity (abbreviated as EC) or total dissolved solid (abbreviated as TDS) meter. SDSU Extension provides this service throughout South Dakota; however, producers can purchase their own meter. It can ride along in the pick-up, side-by-side, or saddle bag to test water sources prior to pasture turn-out.

Meter Selection

Hand holding a TDS meter in a water container.
Many common online supply stores sell EC/TDS meters. Courtesy: Canva

There are several makes and models of EC/TDS meters. Key things to consider:

  • Don’t buy the cheapest one. You get what you pay for. You can also get bells and whistles you don’t need. The average cost for a meter that tests for total dissolved solids and the temperature of water is $70. Meters may be only EC or only TDS, or it may include both EC and TDS. Many common online supply stores sell meters (including, Gemplers, NASCO, Amazon, Hannah Instruments, and others).
  • Do I want an EC or TDS meter? It does not matter. Both types are quick methods to estimate total dissolved solids in water. You may also hear of total dissolved salts. The dissolved minerals in the water conduct electricity. Distilled water is a poor conductor of electricity; however, as more minerals are dissolved, the more readily the water conducts electricity.
  • Select a meter that can test at a high level of total dissolved solids. For example, an electro-conductivity meter should be able to test as high as 20.00 MilliSiemens per centimetre (abbreviated as mS/cm).
  • When looking at a livestock water quality interpretation table, confirm if the values are measured by EC or TDS. If the table is in TDS, and your meter is an EC meter, you will need to convert from EC to TDS. Use Table 1 as a conversion table.

Table 1. Electro-Conductivity (EC) and Total Dissolved Solid (TDS) Conversion Table

Electrical Conductivity
Approximate
TDS
Conversion
Factor*
μmhos/cm
mmhos/cm
μS/cm
mS/cm
mg/l or ppm
-
100
0.1
100
0.1
50
0.50
500
0.5
500
0.5
300
0.60
1,000
1.0
1,000
1.0
650
0.65
1,500
1.5
1,500
1.5
1,050
0.70
2,000
2.0
2,000
2.0
1,450
0.72
2,500
2.5
2,500
2.5
1,850
0.74
3,000
3.0
3,000
3.0
2,250
0.75
3,500
3.5
3,500
3.5
2,650
0.76
4,000
4.0
4,000
4.0
3,050
0.77
4,500
4.5
4,500
4.5
3,500
0.78
5,000
5.0
5,000
5.0
3,950
0.79
6,000
6.0
6,000
6.0
4,740
0.79
6,500
6.5
6,500
6.5
5,135
0.79
7,000
7.0
7,000
7.0
5,600
0.80
8,000
7.5
7,500
7.5
6,075
0.81
10,000
10.0
10,000
10.0
8,200
0.82

*Conversion factor is for natural waters. Source: NDSU Extension: Using Electric Conductivity and Total Dissolved Solids Meters to Field Test Water Quality

Using the Meter

How to use an EC/TDS meter:

  • Construct a simple water dipper for testing your pond (Figure 1). It does not have to be fancy, and could be as simple as a stick with a bottle taped onto it. This allows for the sample to be taken away from the shoreline and that you don’t get bogged in.
  • Dip the jar into the pond to collect the sample for your test (Figure 2).
  • Place the water sample in a container/cup that accommodates the size of the meter. The container can be any clean bottle, jar, cup, or similar container. The electrical probes need to be fully immersed in the water. The meter should not touch the sides or bottom of container.
  • Insert the meter into the sample, making sure the electrical probes are immersed and that the probe is not touching the sides or bottom of the container (Figure 3). The digital reading will settle once it adjusts to the water temperature. Refer to our Livestock Water Quality Interpretation Factsheet to determine quality.

A plastic bottle tapped to a stick.
Figure 1. Construct a simple water dipper.
A young man collecting a water sample from a pond using a water dipper.
Figure 2. Collect a sample from your water source.
TDS meter immersed in a water sample.
Figure 3. Insert the meter into the sample to collect your reading.

Sample Submission

After the quick test is performed, the sample may need to be sent in for further testing. For a list of testing locations, refer to Feed and Water Testing Laboratories factsheet.

If you need assistance selecting a meter or interpretation of results, please contact Robin Salverson, SDSU Extension Cow Calf Field Specialist.