unexpected discover on Eheim Pro canisters

nvision

nvision

what the heck is a pl*co?
Dec 11, 2002
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Sunnyvale, CA
jau.smugmug.com
unexpected discovery on Eheim Pro canisters

noticed this while cleaning the filters. on the 2026 and 2028, look thru the outlet spout (not inlet), through the flow indicator ball. now isn't that a 3/8" exit opening? that's quite small compared with the specified 5/8" overall tubing for the return outlet system. i wonder why that is; kinda defeats the purpose and advantages of a wider tube diameter. i would imagine the extra water volume in the hose actually reduces the overall flow? odd.

this may also be found in the original Pro series and wet/dry canisters, not sure. i only own the ProIIs. but anyway, just some thoughts for the day.
 
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the gallons per minute is the same in the smaller part in the housing and the return pipe to the tank. but with smaller diameter the speed of flow is faster and if I remember the fluid dynamics right smaller tubeing section means less pressure on the walls of said tubeing.

with that in mind I might say they designed it that way so the point of failure would be less likely to be inside the filter houseing where a repair would be more expencive.

not that we want it to fail anywhere... would make for a big mess, but from the manufacturers stand point I guess it makes sence to engineer greater stress on a part that is cheaper to repair if..... if it sprouts a leak in the middle of the hose.
 
that's interesting. so to that point, i wonder why eheim selectively implement different sized tubing for their classic canisters? wouldn't the same physics apply? i guess that's what got me wondering in the first place.
 
A small reduction like that will add to the pressure in the system, but it is rather minor compared to the restriction of tubing over a long length. Actually, the friction as flow goes round the ball is probably more important.
 
that's a good point. i'd always thought the ball design is a bit tacky. the rubbery layer of the ball actually wears out over time, and i've had the ball get stuck in its clear compartment chamber. hypothetically, it's not enough to stop the flow, but enough to a small degree to impede an otherwise streamlined path through the remaining tubing.
 
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