Project

Building Plastic Mini-Kegs: Projects

The hobbies of gardening and brewing come together on more occasions than simply hop and malt growing. These garden sprayers have been modified to work as kegging systems.

When we start out in this hobby, homebrewers typically package their beers in bottles.  It doesn’t take long for the homebrewer to realize that bottles can be a real pain: they take up a lot of space and are very time consuming to wash, sanitize and fill.  So, the logical choice is to evolve to kegging. Stainless steel kegs are the best choice for long term storage, but there are less expensive alternatives that work well for the short-term (up to three weeks).

Plastic keg systems
Plastic kegs are a good alternative, because although they have a degree of oxygen permeability, they can sustain a beer for up to two weeks (possibly longer) without ill effect. Also, they are available in a wide array of sizes from 1 to 20 liters, so you can choose a size that you and your brewing friends can drink before the beer has a chance to oxidize. Another bonus — many of these kegs are small enough to throw in your kitchen fridge so no need for a kegerator!

All these keg systems work off small disposable gas bottles (soda chargers) that are used in devices such as soda-water dispensers, or those home made soft drink machines you get at department stores. The CO2 source in these keg systems is not meant to gas the beer. The beer gasses itself through priming sugar that you add to the keg, similarly to the priming done in a bottle. The CO2 source that you use helps maintain the pressure once you start pouring the beer. These keg systems have a device that allows you to add small amounts of CO2 to maintain the pressure in the keg when you start pouring. The procedure is simple:

  1. After fermentation is finished the beer is transferred to the plastic kegs.
  2. You add a measured amount of priming sugar to the keg.
  3. Seal the keg and let stand for two weeks to naturally carbonate.
  4. After two weeks the beer will be carbonated and you put the keg in the fridge.
  5. Pour from the keg through its tap, adding gas from your CO2 source to maintain the pressure.


Homemade plastic kegs

It may surprise you that these kegs are the plastic spray bottles you find in the gardening section of any hardware store. They are the ones made of thick food-grade plastic that have a pump in the center of the lid. Be sure to find one that has an opening at the top big enough to get your fingers in. This is necessary to fit a tire valve.

With a few quick modifications, your sprayer can function for short term storage.

Modifying the plastic kegs
The first job is to fit a tire valve to the keg above the liquid line (tire valves can be found at any tire store). To do this, drill a hole equal to the size of the tire valve, then fit the valve into the hole, being sure to create an air-tight seal with a rubber washer and food-grade glue. You need to get the chrome plated or stainless steel valves that are safe for beer. You normally should replace the rubber washer that seals it to the container with a new one available from any hardware store.

Next job is to check the lines. You should take them apart and remove any inbuilt filters. These filters will cause the beer to foam up. Be sure to replace the lines with foodgrade lines if the hoses from the sprayer are not adequate.

Change the fittings
I have found that in many of these containers the fittings do leak over time. The original fittings are not designed for long-term pressure and most will slowly leak. What I recommend is to remove all the original fittings and replace them. Buy some hoses from your brew shop (or use the ones that came with the sprayer if they are adequate) and crimp them on to the keg (if you don’t have the tools to do this, most homebrew shops can help you out). As for the tap, picnic taps, also available at brew shops, will do the job nicely. Fit one of those as a tap and crimp this as well.

The next job is to modify the pump mechanism. You don’t want to use the pump built into the sprayer as it will oxidize your beer and has a lubricant on it that will impart funky flavors. To modify the pump you remove the pump mechanism from the lid. Take out the pump handle, then use cleansers and sanitizers to get all the grease out of the pump housing. At the bottom of the housing you will find a one-way valve. Remove it and seal the hole with a screw and a washer. Another way to seal the valve is to use a food grade glue. This is what we have done in this example. Either way, seal the pump and sanitize it — that’s it!

These kegging setups dispense with the use of C02 injectors like soda-streamers.

Supply of CO2
The final item needed is a source of CO2 for your keg. We opted for a soda-stream dispenser that takes a small CO2 cylinder available in most department stores. All you do is modify the dispenser by fitting a tire valve to its hose. This valve can then be used to pump CO2 from those disposable CO2 sources into your keg through the tire valve you installed earlier.

Using the system
Let’s start with cleaning the keg. First, never scrub the keg as it will scratch and these scratches will harbor germs. The kegs clean very easily with either a hot caustic solution or bleach. Just add the solution and hot water and seal the keg. Make sure it gets into the top and runs through the line as well. Also, be sure to rinse the keg thoroughly to remove all traces of the cleaner before use (don’t forget to rinse the line).

Next you will need to prime the keg with sugar. This will depend on the volume of the keg, but a heaping teaspoon of priming sugar per quart or liter of beer is not a bad place to start. Transfer your beer to the keg after it has finished fermentation. Let the plastic keg sit at your fermentation temperature for about two weeks to build up pressure. After two weeks it can be poured as you wish, just put it in the fridge first to chill. As you pour your beer you will notice the pressure will drop and the pour will slow. This is when you will need to put more CO2 into the keg to maintain the pouring pressure.