How to Keg Beer Part 3: The Essential Guide to Filling a Keg

If you’ve read through parts 1 (what you need) and 2 (cleaning and prepping) of our essential guide to how to keg beer, you should be ready to start filling your keg up with your favourite homebrew. While it is possible to muddle through this process by yourself, it’s a good idea to see what’s involved.

Learning how to fill a keg isn’t exactly rocket science, but there certain tricks of the trade that are worth knowing if you want the process to go smoothly each and every time. So, kick back with a cold one and see what it’s all about.

Filling a Keg with Homebrew

How you fill your keg is largely dependent on what type of fermenting vessel you are using. For glass or plastic carboys, or buckets that aren’t fitted with a tap, you will need to siphon the beer off into the keg. For those fermenters that do have a tap, you can run it off directly into the dip tube. Finally, if you use a pressurised fermenting vessel, you can use co2 to push your beer into the keg directly.

How to Fill a Keg Using a Siphon

Glass and plastic carboys are extremely popular fermenting vessels, and filling a keg from one is much like bottling. You will need to siphon the beer into your keg through the lid. This requires you to depressurise the keg and carefully, partially remove the lid. You can cover any gaps with sanitised tin foil or kitchen roll to prevent excess oxygen entering.

Once ready to siphon, insert your sanitised hose, preferably to the bottom of the keg to avoid splashing and introducing excess oxygen. Start the siphon, and carefully monitor how much beer is entering the keg.

How to Fill a Keg Using a Tap

If your fermenting vessel is fitted with a tap, you can fill your keg without removing its lid, reducing the chance of oxidation. You will still need to release the pressure from within the keg before you start filling; if the pressure in your keg is greater than in the fermenter, it will not fill, and is more likely to release a burst of co2 into your fermenter, disturbing the sediment.

Once depressurised, fit a sanitised hose to the tap on the fermenter, and fit the other end onto the beer disconnect on your keg. This will allow the beer to enter the keg via the dip tube, preventing it from splashing. Open up the tap on the fermenter and let the beer flow into the keg. If the flow stops, you’ll need to release pressure from the keg. The easiest way to do this is to fit an open tap or valve onto the gas disconnect, otherwise you can simply pull the release valve when necessary or partially open the lid.

How to Fill a Keg From a Pressurised Fermenting Vessel

This method will entirely remove the risk of oxidation as long as your keg has been purged. Release most of the pressure from your keg, then hook up a hose between the tap on the fermenter and the beer disconnect. Fit a co2 tank and regulator onto your fermenting vessel, set it to around 5 psi, and let the beer flow into the keg.

You will need to release pressure from the keg every now and then to ensure the pressure in the fermenter is always greater. The easiest way to do this is to fit a valve to the gas ‘in’ connector on the keg, leaving it partially open during the transfer.

Avoid Overfilling Your Keg

Many first time keggers fall into the trap of overfilling their kegs. This can have disastrous consequences, especially is beer escapes through the gas disconnect and into your co2 regulator when force carbing — effectively destroying the regulator. You can get a gas disconnect fitted with a check valve to prevent this issue, but it’s best practice to avoid overfilling in the first place.

You need to leave a certain amount of head space in your keg to aid in carbonation and prevent beer escaping out of the gas disconnect. One easy way to do this is to weigh your keg as you fill it; one kilogram more or less equates to one litre of beer.

If you put your empty keg on a heavyweight scale, zero it and start filling, you can keep an eye on how many litres of beer are in the keg at anytime. If you’re using a corny keg, it’s a good idea to stop when you get to around 18 litres. Using scales can also help you keep an eye on how quickly the beer is flowing, or if it’s stopped, either due to a blockage or too much pressure within the keg.

If you don’t have heavyweight scales, you can prepare in advance by ensuring your fermenter is marked to measure the amount of beer inside. In this way, you can simply count down the litres. Alternatively, you can fill your keg at a slight angle. Raise the dip tube side of the keg by around 1 or 2 cm and fit a short hose to the gas disconnect, then fill your keg until beer runs out of the hose. When you put the keg level, the beer will be beneath the gas disconnect, leaving adequate head space.

Seal and Pressurise

With your keg filled up, you will need to seal it up. Sealing the keg ensures the co2 remains inside when carbing your beer, and also prevents any oxygen from getting in. If you transferred under pressure from a pressurised fermenter, your keg should already be sealed — you can check by attempting to push the lid down, if properly sealed, it shouldn’t budge.

If you had to loosen the lid to make the transfer, simply refit it, taking care to sanitise and ensure the gasket is properly seated. Switch on your gas tank and set the regulator to around 10 psi before connecting the gas disconnect. This prevents any foam from potentially entering the regulator if you overfilled.

Connect the gas, and properly seat the lid if necessary, all the while listening for gas leaks. Spray no rinse sanitiser on the disconnects and around the lid to check for any leaks that you can’t hear — if the sanitiser bubbles, co2 is escaping. Finally, purge any oxygen from the tank by releasing it using the pressure release valve. Do this 2 or 3 times to be sure you have only beer and co2 inside.

If all has gone well, you should now have a sealed keg filled with homebrew. The next step is to cold crash and carbonate your homebrew. We’ll cover this in part 4 of our essential guide on how to keg beer.