Hach DR/2010 Instrument Manual page 22

Figure 3 Installing the Pour-Thru Cell
4. Pour 25 to 50 mL of demineralized water into the funnel and allow the
funnel to drain. If necessary, move the stand pipe up or down to
achieve the proper liquid level. When properly adjusted, the funnel
drains smoothly and stops draining at the correct level.
The drain tube attached to the stand pipe must drain freely. It should
always remain below the outlet of the stand pipe, and should not run
horizontally any more than necessary. Preferably, the tube should be as
short as possible with the outlet end inserted into a drain (or suitable
collecting vessel if treatment is necessary before discharge).
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