Using Automatic Samplers with Flumes and Weirs

Automatic Samplers (also called autosamplers or simply samplers) collect and store water samples for laboratory analysis without the need for operator intervention. When used in conjunction with a flume or weir, automatic samplers can collect samples that are truly representative of the flow stream.

When a sampler takes a sample, it draws the sample from the collection point through a suction (or sample) line to the pump. The sample flows past a liquid detector, which senses and quantifies the sample. After the liquid detector, the sample is routed via a distributor arm into one or more sample bottles.

For installations where no primary device is present, or where the sampling is only temporary, a weighted strainer may be attached to the inlet end of the sample line. The strainer helps to prevent clogging of the suction line and can aid in keeping the sample line in the right location. Strainers typically have a series of holes down the body of the strainer to reduce the likelihood of solids blinding or clogging the strainer.
When sampling from a primary device (flume or weir box), rigid stainless steel sampler tubes are commonly used. The tubes are attached to the top of the primary device and extend down into the flow stream. The sample line is pushed on to the top of the sampler tube to make a watertight connection. Sampler tubes can be recessed in a cavity down or can be flush mounted against the device wall.

removable stainless steel sampler tube in a fiberglass Palmer Bowlus flume

Sampler tubes can be provided with all flumes except short length Palmer Bowlus styles (where the point of measurement is upstream of the flume itself) as well as in weir boxes.

Examples of automatic samplers include: