co2 tank sizes for kegging startup

I'm going to start kegging my 5 gallon batches. I've already bought a reconditioned corny keg. And I'm fairly certain I'm going to get a dual gauge regulator so that I can eventually hook up two kegs and control the pressure separately. However, I'm having trouble deciding on co2 tank sizes. I'm open to suggestions and curious what the ideal setup is. But here is what i'm leaning towards.
20lb aluminum tank to force carbonate and then 20 oz co2 tank to maintain pressure and for use as a more portable option. thoughts?
or
10lb co2 tank to force carbonate with 20 oz to maintain pressure

However, I've heard various things that 20oz paintball tanks aren't safe. Is this a misconception? Are the tanks themselves food safe or is the gas they put in the tanks not foodsafe? If you have a tank that has had non food safe co2 in it and you empty it and fill it with food safe co2 will it be food safe?

I don't really get the popularity of the 5lb tank. the 10lb tank is really not that much bigger in comparison however, you get twice as much space. What are everyone elses opinions in regards to co2 sizes and the ideal set up? Perhaps someone can convince me to just buy a 5lb co2 tank and just use for for carbing and portable use.

 

Why the two cylinders when you've only mentioned one dual-body regulator?
I'd go with a Craig's List 10 pound tank that's fit to be exchanged and call it a day...

Cheers!

 

There is no such thing as food safe co2 it's all the same.

I use a 20 to force carb and a 5 to serve in my kegerator at home. I then use a 20oz paintball setup for my portable. I just posted a pix of that setup here: http://www.homebrewtalk.com/f51/looking-quick-cheap-co2-rig-480221/

Where I live gas for a 20lb is about the same as a 5 lb but you get more gas. 20oz costs even more at $3.50 a fill. Since I use my
Portable a lot, I'm going to convert one of my 20lb tanks into a siphon and use a fill station adapter. But I just happen to have a bunch of cylinders.

normal setups are 5lb. If you can go 20, do it. It saves $$$, but it all comes down to space.

 

I have a 20# attached to my keezer, and a 10# & 5# for everything else. All craigslist finds. I paid less than $100 for all 3.

I have issues trading my 10# tank though. They're not real popular, and no one seems to stock them. I have to call a few days in advance to make sure one is available for a swap. Hmmm... I guess it's not that big of a deal.

If you plan on purging, carbing, and serving with one tank, I'd recommend the 20#. Get a 5# and use it only for travel.

 

A 5 lb costs $15 to fill vs. $18 for a 20 lb where I'm at, so I recently acquired a 20 lb....however a gas leak will now cost me a few bucks more....haha.

 

Like insanim8er, I have a 20lb, 5lb and use a 20oz for portable serving. I use to have a 10, but one day when I went for a trade they were out of 10's and gave me a 20 for almost the same price. But I'm old and weak. I bring my 5lb up from the basement on transfer days to purge and push. The 20 is too heavy to move around, so it's only used to serve and force carb. It lasts a long, long time even though it supplies gas to multiple keg in both basement and upstairs beer fridges. A 20oz is the way to go for serving away from home.

 

Thanks for the help! Sounds like 20oz, 5lb, 20lb is the way to go. There is a new 20lb co2 tank on ebay now for $109 and free shipping is that a good deal? My craigslist here in saint louis is pretty bare as far as co2 tanks though. I also like the idea of filling rather than swapping a whole lot more seeing that i'm most likely going to buy new.

Also, If i get a 20lb tank and use it for force carbing and then I want to fill up my 5lb or 20oz tank from my 20lb will I be able to do that? or do I need this syphon thing you speak of. not exactly sure what it is use for.

 

Unless you've already identified a convenient location that will refill tanks on demand, you'll likely end up swapping tanks, in which case it's best to go as cheap as possible on the front end...

Cheers!

 

Co2 tanks are filled with liquid co2. The head space is filled by gas from the liquid and dispensed out.

A dip tube will dispense liquid co2 out of the tank because it draws from the bottom. This allows you to transfer liquid co2 into another vessel

It also means you can't (well shouldn't) use it for gas. Some will tip the cylinder upside down... Not safe.

So really it's best to just pay to swap/fill the 20lb unless you have two 20s to convert one. (That's what I'm planning)

It's also best to swap tanks vs fill, so you don't pay for hydro. But paintball tanks are always filled.