Churn Operation

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Detailed Description

Training video demonstrating proper water quality churn operation.


Date Taken:

Length: 00:06:03

Location Taken: Reston, VA, US

Video Credits

Scott Dennis, Michael Manning, Stanley Strobialowski, Cherie Miller



Welcome to USGS video training for collecting and processing water quality data. The USGS has a reputation for water data that are reliable and impartial.  Our data are used by many agencies and scientists who seek to understand and manage our Nation’s water resources. The water mission area of the USGS has an important responsibility to collect data that accurately describes the physical, chemical, and biological attributes of our Nation’s water systems. To accomplish this, USGS has developed a National Field Manual for the collection of water quality data. The National Field Manual provides documentation, and consistency in our scientific methods. It maintains the accuracy of our data, and it sharpens our technical expertise. This video series supplements the National Field Manual with focused training on selected field techniques.

This video presents the types, limitations and operations of churns splitters.

Churns are simple to operate, easy to clean, constructed of polymer or plastic material

and available in 8 liter and 14 liter sizes.

Churn splitters or churns are used to combine subsamples as they are collected

from several points in a stream or river.

The churn is then used to split the combined water sample into sample bottles that represent

the suspended and dissolved concentrations in the stream or river.

The advantages and limitations of churns are described in table 2.6

in chapter 2 of the National Field Manual.

The plastic churn should be used to process samples for inorganic analysis.

The polymer churn can be used to process samples for either inorganic

or nonvolatile organic analysis.

The original spigot on the plastic churn contains a metal spring

that was found to be a source of metal contamination and must be replaced

if the churn is used to process samples for trace element analysis.

The spigot can be replaced by the manufacturer with non-contaminating components.

There are several limitations to churns – Including sediment size and concentration.

The size of the particles cannot exceed 250 microns.

The total sediment concentration cannot exceed one thousand milligrams per liter.

The maximum volume for the 14 liter churn is 13 liters,


and the maximum volume for the 8 liter churn is 7 liters.

After all samples are withdrawn from the churn

the water level inside the churn should be at least 2 inches above the spigot inlet.

Churns are not approved for some microbiology sample processing.

See chapter 7 of the National Field Manual for additional details.

While wearing disposable gloves, remove the churn splitter and inner bag from the churn carrier

and place it on a level surface.

The dirty hands team member churns the splitter throughout sample processing

at a uniform rate of 9 inches per second by raising and lowering the disk inside

the churn with smooth even strokes.

When churning, the disk should touch the bottom of the churn on every stroke,

and the stroke length should be as long as possible without breaking the water surface.

For proper disk alignment, insert the disk with the grove mated with

the alignment guide inside the churn.

Before withdrawing any sample pre-mix the sample by churning with 10 strokes

to uniformly disperse the suspended material.

The churning rate should be about 9 inches per second.

Inadequate churning can result in non-representative samples.

If the churning rate is significantly greater than 9 inches per second,

or if the disk breaks the water surface excessive air is introduced into the sample

and that could affect dissolved gasses, carbonate, pH, and other sample characteristics.

Do not interrupt the churning or subsampling process.

If an interruption occurs, reestablish the churning rate to remix the sample

by churning ten strokes at the proper rate before continuing.

As the volume of the composite sample in the churn decreases,

adjust the stroke length to maintain a churning rate of about 9 inches per second

and continue to avoid breaking the water surface within the churn.

Samples should be withdrawn from the churn in order of volume, largest to smallest.

Empty the churn after all bottles have been processed.

If the churn will be reused, disassemble it and clean it onsite

while it is still wet, as described in the National Field Manual chapter 3.

If the churn will not be reused during the field trip, rinse it with DI water before it dries out,

Place it in a plastic bag and in the churn carrier for transportation

back to the office laboratory for cleaning.

Complete the field forms and notes to document the type of churn used.

For additional information regarding selection, cleaning, collection, processing and churn splitters

see chapters 2,3,4 and 5 of the National Field Manual.


Voice and Demonstration

Stanley Skrobialowski

Michael Manning

Cherie Miller

Courtney Killian


Video Filming and Editing

H. Scott Dennis