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Re: Measuring Flow (was APD V3 #1387

Hello Duane,

The most _covenient_ way to measure water flow is to use indirect
methods that measure some parameter related to flow and then calculate
the flow rate. However, indirect flow measurements are notoriously
inaccurate, even in the laboratory, because of sensitivity to the
geometry of the sampling site. For a hobbyist, the most practical
solution is direct measurement of flow.

Assuming, that a value +/-10%, or better, is accurate enough for you,
the simplest method is to immerse a measuring cylinder, or any container
of known volume, in the aquarium (keeping aquarium water out of it!). If
the container volume is less than 1 % of the aquarium volume, the rise
in water level in the aquarium will be insignificant.

To measure flow, just move the container under the filter outlet and
time how long it takes to fill your container. The water level in the
container and the water level in the aquarium should be kept
approximately the same, if possible. That is your measurement -- time
necessary to fill a known volume. The rest is just arithmetic.



> Date: Fri, 12 Nov 1999 20:56:22 EST
> From: AquaServe at aol_com
> Subject: Measuring water flow
> I know this is not a plant question but I am hoping someone can help me.  I
> would like to measure the total flow rate of a few different filters at given
> times.  What device do I need to do this and where can I get it?  I would
> imagine I need something that would be plugged inline to a filter outflow but
> I would also like to measure flow rates on outside box filters.  Would I be
> able to use the same device for both box and and canister filters?  Thanks
> for any help.
> Duane