> For the complete documentation index, see [llms.txt](https://help.sbtinstruments.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.sbtinstruments.com/troubleshooting/qc-test-fails/check-liquid-uptake.md).

# Check liquid uptake

Make sure your BactoBox® draws liquid from the vial. If not, replace the parts in the flow path one at a time.

Your BactoBox® measures the conductivity of the liquid it draws in. If no liquid comes in, the conductivity reads too low. Then a part of the flow path is most likely clogged. Replace the parts one at a time, so you know which one was the cause. If the QC test fails with another code along the way, follow that code in [Error codes](/troubleshooting/error-codes.md).

## Step by step

{% stepper %}
{% step %}

#### Watch the vial

[Run a QC test](/maintenance/qc-test/run-qc-test.md) again with fresh vials at room temperature. When the measurement starts, watch the liquid level in the vial. It should drop.

* **The level drops.** Liquid reaches your BactoBox®. [Contact support](/troubleshooting/contact-support.md).
* **The level does not drop.** Go on to the next step.
  {% endstep %}

{% step %}

#### Replace the external filter

Replace the [external filter](/item-register/individual-items/external-filter.md), as shown in [Install tubing kit](/getting-started/installation/install-tubing-kit.md). Run a QC test. If it passes, you are done.
{% endstep %}

{% step %}

#### Replace the flow cell

[Install a new flow cell](/getting-started/installation/install-flow-cell.md). Keep the old one, so you can try to [recover it](/troubleshooting/qc-test-fails/recover-a-flow-cell.md) later. Run a QC test. If it passes, you are done.
{% endstep %}

{% step %}

#### Replace the tubing kit

[Install a new tubing kit](/getting-started/installation/install-tubing-kit.md). You can order a spare [tubing kit](/item-register/bactobox-r/bactobox-r/in-the-box/tubing-kit.md) from SBT. Run a QC test. If it passes, you are done.
{% endstep %}

{% step %}

#### Contact support

QC test still fails? [Contact support](/troubleshooting/contact-support.md). Tell us which parts you replaced.
{% endstep %}
{% endstepper %}


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