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1/4" Auto-Siphon Sucking Air?

We have one of the larger 1/4 inch auto-siphon tubes and racking cane.

When it gets about 3/4 done, the siphon starts sucking bubbles through the tube and makes a hissing noise.

The tip of the cane is fully submerged when this happens and the tube is full of beer the entire time.

It’s just that last short bit during the racking process that it starts blowing the bubbles through the tube and making the hissing noise.

I’m worried that I just oxidized 10 gallons of beer!

Anyone else experience this? Any idea why it would do this?

When I moved into my new house last year, I bought a new racking cane and tubing. I noticed the same bubbles in the line and sure enough tasted oxidation on those first few batches.

Turns out the tubing was just a smidge too large and wasn’t snug enough with the racking cane.

Had to go and buy smaller size tubing.


I take my 3 piece wine thief sanitize it then put a 2 couple inches of wort in the outer tube problem solved.

Sorry…I’m not visualizing how this looks and works?

This works if the problem is that the seal of the gasket between the inner and outer tubes (the piston if you will) is not tight. As the hydraulic pressure of the beer in the upper vessel decreases, but the suction exerted by the syphon remains strong, there is more of a tendency for air to get sucked past the seal. By putting some beer in the outer tube above the gasket, you get small amounts of beer sucked in instead of air.

Another way to address the problem would be to decrease the vertical distance between the two vessels. That lessens the sucking pressure of the syphon thus extends the time until the air will begin to get sucked in.

Or you could buy a new autosyphon and hope it has a better seal.

A bad seal between the syphon cane and the tubing can also cause bubbles, but if that was the cause you would get them right from the beginning - it wouldn’t wait till the end of the racking to start.

Got it. Makes sense now.

I’ll try that next time.


Do not store your auto siphon assembled. Leaving the siphon assembled distorts the rubber at the bottom of the racking tube. This will cause a poor seal.

Yea, we don’t. The tube stays attached to the cane…because it’s on there so tight. But the can comes out of the body and we hang both to dry separately.

Yea, we don’t. The tube stays attached to the cane…because it’s on there so tight. But the can comes out of the body and we hang both to dry separately.[/quote]

I use hot water to make the tubing more flexible to twist off the racking cane. I use Starsan for lubrication to slip it on. Still I always worry my big hands will break the cane some day.

I’ve gone through a few canes over the years. Normal use will cause small microcracks to form which will eventually cause the thing to break. To be expected really.

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