Siphoning is one of the necessary evils for homebrewers. Unless you are fortunate enough to have a large RIMS/HERMS brewing system with wort pumps and conical fermenters, and pumps for transferring between fermenters, you have probably had to siphon your beer at some point. We siphon to move wort to the fermenter, we siphon to transfer beer to a secondary, we siphon finished beer to a bottling bucket or keg. This leaves the trub or sediment behind, but siphons can be a challenge to work with.
The big risk here is oxygen – which is an enemy of finished beer. Oxygen in large quantities will rapidly spoil your beer, but even in smaller quantities it will destroy long term flavor stability and also contribute to chill haze and clarity problems.
Siphoning the Old Fashioned Way
A siphon is an ancient device that uses gravity to transfer liquid from one vessel to another. As long as the liquid level in the destination is lower than the source, it will transfer the liquid until you run dry. The first challenge is that you have to “prime” the transfer tube with some water or wort in order to get the flow started. The second is that you need to prevent the siphon from getting plugged up with trub and sediment, which is an issue both after the boil and after fermentation.
When I started brewing, most of use primed a siphon by filling the hose with some sterile water, and clamping or plugging one end. The clamp was then released once we had both ends positioned, and it would siphon away. The problem with this approach was the difficulty of filling the siphon without contaminating it, and keeping it full while positioning the two vessels. It was not an ideal solution.
The Siphon Cap
In the early 1990’s several companies introduced a cap for carboys that sealed the top of the carboy off but had two holes. One hole was carefully sized to match an average siphoning wand, and you actually blew/sucked air through the other hole to create a vacuum (or overpressure) that would initiate the transfer.
This was a slight improvement over the old manual method of priming with water, but you ran the risk of introducing air (or germs) from your mouth into the beer. Again, not an ideal solution.
Many brewing stores now have a device commonly called the “auto siphon” for sale. These are made from two tubes. The outer tube has a one way valve on it near the bottom and sits in the wort you are moving, and an inner tube has a seal that lets it act as a piston. The hose is attached to the inner tube. To operate it you pump the inner tube slowly which brings wort into the tubes on the upstroke, and forces it into your siphon tube on the downstroke.
With just a few pumps you can get the siphon primed and the wort moving easily, so this seems to be the best of both worlds. However, I’ve had problems with the seal on several of these devices. If you have even a slightly poor seal between the inner and outer tube, that seal will let air in. Once the siphon gets going it can be even worse since the siphon acts under a vacuum – drawing in more air as it goes. This will show up as bubbling in the siphon – and can be a real problem as you certainly don’t want to contaminate your finished beer with air.
A workaround is to add some sterile water to the outer tube outside of the gap – so if your seal leaks it will draw in sterile water instead of air. However, this takes us almost full circle back to the “old fashioned” method since I now need to prime my siphon with sterile water before starting, and also you need to worry about the water in the auto siphon as you pump it for priming.
Minimizing Trub/Sediment Ingestion
The other problem with siphons is that it can be hard to separate the wort from the trub. Earlier in my brewing career I obsessed with minimizing the amount of trub from the boiler and sediment in the fermenter. I used to attach cloth to the bottom of the siphon wands to try to filter out the sediment.
Lately I’ve realized that if I’m careful with the wand when transferring, not that much really comes over. So I’ve given up my cheese-cloth filters and simply try to keep the siphon wand above the sediment as long as possible, and tip the vessel at the end to avoid sucking up too much trub. Also I try really hard not to disturb the sediment when transferring.
A Better Siphoning Option?
So I’ve come to the end of my rant on siphons. Moving to a conical fermenter has helped, at least with fermentation transfers because I can separate the wort from the sediment before transferring, and also don’t need to use a siphon to transfer the wort. Today I still use the auto siphon if needed, but do add some sterile water first as insurance against leaks. Its not ideal, but I like the ease of use of the auto-siphon, and I’ve found a few of them that seal pretty well and don’t leak much.