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Flow meters are used to measure the amount of liquid flowing through a pipe.
It’s not hard to see why this is an appealing proposition for a distillery, which is full of moving liquid that must be tracked and measured constantly.
Unfortunately, most flow meters are unsuitable for spirits. Typical magnetic flow meters will not properly account for the varying densities of your different spirits products. To achieve accurate measurements with spirits, you must upgrade to a Coriolis mass flow meter. These meters have sufficient accuracy to handle the varying density and temperature of spirits in a typical distillery, but typically cost thousands or tens of thousands of dollars.
But even that isn’t necessarily good enough – to achieve accurate performance, you must operate the flow meter at or near its designed flow rate, and you typically need to have a long section of hard pipe before and after the meter, to ensure that your flow is as smooth as possible. These requirements are challenging to meet in a typical craft distillery setting.
In general, TTB standards require you to perform spirit measurements with a high degree of precision, and your recordkeeping will illuminate the issue if you attempt to use an unsuitable flow meter. You will find yourself running into Proof Gallon mismatches where you wouldn’t expect them, and they can be challenging to address, especially if they’re in the past.
With all of this said, the limitations that make flow meters generally unsuitable for spirits do not apply to water. If you are looking to use a flow meter only for measuring water additions, you are much more likely to be successful. Still, flow meters should be periodically checked for accuracy (e.g. by weighing out a known volume).
