Buying lots of soda or sparkling water can get a bit expensive and it is back in vogue.    I remember years ago there was a DIY soda machine you buy at K-mart.  I had one which my be where my love of soda water started.   

One of my favorite drinks is Amoretto and soda water. 

I developed a taste for it when I was stationed in Rota, Spain during Desert Storm/Desert Shield in Oct 1990  After staying in the BOQ for months, but figured IF I am stuck in spain for the duration of war, (who knows how long it might last),  I decided to move outside the base to the local down of Rota.  

A hotel was found on the beach.  What fun!  My room overlooked the beach,  with a balcony, with a great view.  Yes there were topless sun bathers (not many but a few and those.....well not).  Overlooking the beach is where I sipped Amoretto and soda.   I guess I mostly liked the refreshing taste of the almond flavoring.  I have since substituted Almond flavoring and Sweet & Low.  Just as good but a lot less heady refreshment. 

Back in 1976 when my  Soda Stream machine broke down, I just took it apart to figure out how to fix or re-engineer it.  I came up with an extremely cheap method of making it at home.   

Strangely, after the 70’s the Soda Stream just seem to disappear from the commercial on tv and the stores.  Now 30 years later, I found at Office Max that the SodaStream company had redesigned their product and the are actively marketing again.   They also package many favorings to go along with it.   It certainly has a much better designed than the original.

OK, I KNOW you just want the details of how to make yours so here it is.

Basically, it is a small CO2 tank, a regulator, hose Schrader valves, and used water bottles.  It takes no time to assemble.

You could buy a bunch of equipment (I did from ebay) or scrounge around for parts.  The most expensive part is the regulator and bottle but you can find them just about anywhere, new or used.   It is the easiest, the cheapest and best way to go... Ya!

Grab your soda bottle and caps for conversion.  Any bottle which held carbonated soda in it is a good candidate for being able to handle re-pressurization.

You'll need to purchase some Universal Clamp in Schrader Valves  (PEP boys or any auto parts store) the ones I acquired was Camel 30-445,  $6.00 for 4 ea.  A compressor type tire fill valve from Home Depot, a CO2 tank and a regulator.

First take the top from the existing bottles and drill a hole about 7/16" insert the  tire fittings and tighten them up.  Try to find SS if you can, as the brass ones discolor with the carbonic acid (yes that is what carbonated water is...grasshopper)

Just insert the valves into the drilled caps.   Tighten them up and hard work is done. 

Grab the tire fill valve (you bought at Harbor Freight), fabricate a hose of your choice (I use 1/8” plastic piping) to connect the fill valve and the CO2 regulator.    If you need more help than this to explain how to do it, ask a friend or maybe it is just too complex a project.

Set the CO2 regulator for 50-60 psi and you are good.  I have tested (hydro'd) a plastic soda bottle to over 200 psi (filled with water and in a steel containment box) and it did not burst. 

Generally, when you buy soda water at the store, the bottle is only under about 20-30 psi.  Commercial carbonators use about 100 psi.  I cant assure you the bottle has over a 200% safety margin (commercial) and a 6 to 1 safety margin.  50 psi at the regulator is just fine for our needs, I have filled hundreds of bottles which good results.

Here is the best way to do it to make your carbonated elixir of choice.....

The biggest insight I can give you is:  COLD water traps much more CO2 gas than warm water.  

The best results happen when the water is ice cold.  The primary purpose McDonalds fills the TOP of the soda machines is to make cold water for the carbonation process.  The top is actually a heat exchanger to quickly chill the supply water to ice cold water before the carbonator pump.  The secondary purpose of the ice dispenser is to (of coarse) to fill your cup

I usually fill the bottle with water up to the top of the label (leaving a smaller head space for the gas) then put it in the frig to cool.  Loosen the top, to squeeze out all the air and then fill the bottle with gas.  Shaking bottle will mix the gas and water.   Repeat a few times until you get a nice firm bottle.  Done.

Here is a hint:  The more head space you leave in the bottle the less iterations of Fill ‘n Shake you do.   You can even do a one fill method. 

Fill 2/3 full tap water, squeeze out the air, fill to pressure.  Chill in frig and shake before use.  The larger headspace (less water) makes the difference.  It doesn't have a much entrained CO2 as the cold water method, but is still very good.

For favorings, you can use anything!  I used, water, wine, you can make alcoholic sodas, lemon juice and Sweet n Lo, Kool-Aide, repressurize half used cola, hell once I tried to carbonated the wonderful laxative solution you have to drink prior to getting a Colonoscopy...... tasty, but I dont recommend it.