Eheim still sucking air...

[ericbullock]

I can't figure out why this bloody thing continues to suck air. All of the connections are tight and the gasket is intact. The people at Eheim told me to lubricate the seal with Vaseline but I'm a little leary about using a petrolium based product on the seal. I seem to recall reading someting about a silicon lubricant but can't find anything anywhere that looks to be aquarium safe.

Anybody have any ideas on what to use...or further thoughts on what could be causing the filter to suck air? At times it is noisy enough to wake me up at night, but more distressing are all of the tiny air bubbles that get introduced into the water. I'm also concerned about gas exchange and my CO2 levels dropping.

A public thank you to Jim at TFW for hosting the seminar this past month!

-eb-

[rodcon00]

A possible source for the silicon lubricant could be a local scuba diving shop. I have a container for treating the seal on my underwater camera housing. It looks and feels similar to vaseline. I do know that it is non toxic to humans. I have no idea if it is aquarium safe.

Just a guess about a potential source of the air introduction. It could be a piece of hair or particle of dust on the gasket that could allow air to leak into the unit by going around the hair and bypassing the gasket. A similar but inverse problem happens with a scuba diving mask and one strand of hair. The hair will allow water to enter (i.e. flood) into the mask by flowing around the hair.

[Aaron]

Eric,

I'm sure you've checked this, but make sure there are no kinks anywhere in the hoses; especially the inflow lines. Any kinks will cause air to get sucked into the filter.

[ericbullock]

The hoses are actually pretty short...about 2 feet on both the intake and the outlet, so it is pretty easy to verify they are not kinked. Still...a good thought.

Thanks,
-eb-

[RTRJR]

Is the media clogged? Perhaps the impeller is cavitating rather than external air being sucked in? This is not a high pressure/high vacuum application so long as flow is not impeded.

[ericbullock]

Hi there RTRJR - Please forgive my ignorance, but can you define what impeller cavitating is? I think i have an idea, but this is the second time I've heard it mentioned an dhave no idea what it is!

Thanks a bunch...
-eric-

[RTRJR]

If the intake side is impeded (starved for flow), as from too dense packing, clogged media, or valve/hose restriction, a spinning impeller can physically blast the dissolved gases out of the water (by strongly reduced pressure on the intake side). That produces bubbles in the output, even without any air intake to the canister. Water exposed to the atmosphere always has significant dissolved gases present.

Cavitation is most common in the hobby when folk try to restrict flow by clamping down on the wrong side of the pump. It is also most common from bigger stronger pumps than those in the Eheims, but I have seen Eheims cavitate. Heavy duty pond pumps used to be notorious for it.

Eheim "packing" should never be "packed". The body or the carrier section may be filled, but if media compression is needed to reassemble, it is likely over-packed.

HTH