Dumb sponge filter question

[Parzival]

In keeping with my dumb question series...

I picked up a sponge filter at HAW a couple of weeks ago, but I can't see it actually doing anything. There's lots of bubbles coming up through the lift tube, but if there's any water being drawn through the sponge, it's not much. I was under the impression that if I raise the lift tube to just above the water line, I should be able to see some water flowing, and even measure the flow rate. All I see is bubbles and a little splashing. Is that right? I tried putting a plastic air diffuser inside the filter and I got more/smaller bubbles but no difference otherwise. What's wrong?

I really want this filter to work so I can rely on it during power outages and for occasional hospital tank use.

Oh, this is a Hydro-Sponge (TM) Mini HS900. The lift tube is very short, about 2"

[mnemenoi]

I keep mine below the water line for easy water flow. Mine have always worked terrifically, but the flow rate is not tremendous. They do great jobs once they are seasoned and bacteria begin to colonize it. The older they are the better they work. Sometimes a stronger air pump will help, but as long as you are seeing air, it is working. You'll be fine I'm sure.

[troy tucker]

The up tub should be about 8" to 12" . Soulds like you have the bottom sponge part but need a up tub. even the small sponge filter is 6" up tub.
The sponge filter works by lifting water with air. every bubble lifts the water above it. the up tub is where it works.

[Parzival]

Troy, that's kind of what I was thinking. I think a standard lift tube is 5" or more. I just took another look at this one and it's just over an inch long. This thing came in a plastic bag and there's no chance a much longer tube would have fit in there. There's nothing at the hardware store that fits, either.

In other words, I'd try a longer tube if I could find one.

mnemenoi, I believe you're correct, at least in so far that it's doing something, but I think it could be better.

[troy tucker]

how big around is the tub ?

[Parzival]

It looks like the ID is about 7/8", OD is about 1" ... I can get a 6' section on Amazon for $25

[mnemenoi]

Just swing over to a hardware store and buy some PVC, far cheaper...

[Parzival]

PVC doesn't come in 7/8 ID. That's where I started out. (No way I'm buying that from Amazon. I could just get another filter for lot less...)

[troy tucker]

They do have rubber hose. I think that the up tub on undergrav. filter is 7/8 clear tub All the chain stores have it cheeper then that. I would give you some.

[Parzival]

Dumb sponge filter question

At C&D they didn't have 7/8 tubing. I haven't checked a big box store yet.

[Parzival]

I just got an email back from ATI, the folks who make the filter. They told me that all their filters come with a 5" lift tube and that the length of the tube is "critical to the function of the filter." Then they asked me where I got it. I didn't rat out my favorite LFS to them, but I guess I'll bring it up next time I'm over there.

[mistahoo]

Re: Dumb sponge filter question

I was just about to mention that almost all sponge filters come with the lift tube.

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