# The ball in a canister filter..



## Teggy (Nov 5, 2010)

Tough to think of a title for the thread on this one lol. I have a quick question about canister filters. I've noticed on the 3 I've used so far that they all have a ball in the outlet that keeps water from siphoning back if there's no pressure pushing it up. I understand how that works and all, but I don't know why it's necessary. I ask because I recently acquired a second hand filter that works like a champ, but the ball inside is making quite a racket just from banging around it's little ball holding area :lol: . I've tested another filter I have previously without the ball, because it had dropped under the washing machine without my noticing.. lol. Anyway I didn't have any problems with it, but I never did use it like that other than overnight testing in the garage. If I were to remove this ball from the filter to get rid of that noise would I be removing an important mechanism in the filter?


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## nodima (Oct 3, 2002)

That ball is what will theoretically keep the contents of your tank in your tank should the main filter spring a leak. It would prevent back siphoning of the water. I say theoretically, as mine always get gummed up by stuff, and it is unclear how good a seal they would still have.


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## Teggy (Nov 5, 2010)

So it's a fail-safe then. Hmm, it is quite noisy. I'm almost tempted to remove the ball and check it regularly to make sure all is well with it lol.


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## Glaneon (Sep 27, 2010)

My fluval's don't have them afaik.
They have quick stop/close valves.


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## Riceburner (Sep 3, 2008)

My Fluval and Marineland does not have them either.....


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## Jmanolinsky (Jun 4, 2010)

Teggy,

My Eheim 2026, which your filter resembles has a little red ball on the outbound hose. From what I have read, it is simply a flow indicator. It has several lines across the little window to use as a gauge. When the ball is not at the top, it is time to give attention to the filter media. If this was designed as a fail safe, it seems to me it would be on the other hose since the intake is usually placed lower in the tank and the spraybars are typically located near the top. Much more water could be accidentally syphoned from the intake before sucking air than the spraybar.

My two cents,
Jman


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## nodima (Oct 3, 2002)

Re read the OP, and realized I was talking about the balls in the intake strainers.

Not sure about the ball on the outlet side of things, but like the previous poster mentions Eheim has a flow rate indicator there.


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## RRasco (Aug 31, 2006)

Never seen one on my Rena XP2. If I had to guess I would have said it was a check valve, but as some other indicated it may be a flow rate indicator. Not sure why a check valve would be needed on a closed canister. They can't really over flow like a sump. Process of elimination and rationality tells me its a flow indicator.


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## Cyclesafety (Feb 8, 2010)

Took out the ball in my Eheim 2128. Marketing gimmick IMHO. Can't see how it could act in reality as an effective check valve - but the comment got me thinking....


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