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Re: Noisy Cannister Filters

Date: Sun, 28 Oct 2001 12:24:12 -0500
From: "James Purchase" <jppurchase at Home_com>
Subject: Noisy cannister filters

Roger Miller wrote, in a discussion on using a cannister filter as a CO2
"Gas -- I think it's mostly air drawn
through the o-ring seal -- sometimes accumulates at the top of the
canister and that can cause some noise."

I have an Eheim 2260 (the BIG one) that I use on my 130 gallon aquarium. I
don't use it as a CO2 reactor. The intake for the filter is reliably under
18" of water at all times, yet it (the filter) burps and gurgles all the
time. If I shake the unit, a large "burp" of trapped gas will come through
the output tubing and gets released into the tank (it doesn't seem dangerous
and it doesn't smell of sulphur). It has never dawned on me that air could
be being drawn into the cannister through the o-ring seal (its been a while
since I've replaced the o-ring and I don't use any petrolium jelly on the
ring to seal any minor leaks).

Could this be the source of the gas which causes what I have observed?

James Purchase

I have experienced the same thing periodically with my Eheim 2217 filters I 
have on my three planted tanks, but I'd think if air was getting past the 
o-rings that there would be water leakage out of the filter as well.

I surmised that since I get lots of pearling in my leaves with intense light, 
CO2 injection, etc., that the tank water is highly saturated with oxygen and 
that some of this is getting drawn into the intake of the Eheims and collects 
inside the filter, with the requisite burp happening from time to time. Does 
this make sense?

For anyone concerned about airlocking an Eheim cannister, I had a 
conversation with the Eheim North American sales Rep at the 2000 PIDA show in 
Tampa, and he informed me that Eheim Cannisters are engineered with a small 
channel specifically for the purpose of pulling bubbles into the impeller, 
breaking them up, and expelling them thru the output. A huge quantity of gas 
might lock one, but I have been injecting CO2 into Eheims for 2 years now and 
this has never happened to me.