Welding Tips and Tricks

Hi all, first time poster here, been listening to the podcast for the last year and am learning a ton!

I'm looking for advice on what size tanks to buy for GMAW, I'm between picking up a 125cf 75/25 tank off Amazon for $365, otherwise my local supplier sells an 80cf 75/25 tank for $205. Would I be better off picking up 2 80cf tanks for just over the price of a 125?

My thoughts of the 125: more gas capacity in a single tank so don't have to swap out as often, cons it's harder to move around and I do some mobile mig repairs, but those could likely be handled with flux core as they tend to be light duty repairs (metal barricades, bird baths, etc).

My thoughts on 2 80's: more capacity between the 2 tanks, but would have to swap them more frequently at home, they are easier to move around though, higher cost up front with purchasing 2 tanks.

Another concern I have is when I get down to about a 1/4 tank or less, would I have any flow rate issues? I've noticed it with my tig welder that when I start running low on gas I'll have some porosity issues due to what I assume is lack of pressure in the tank. I'm wondering if my actual performance rate of 2 80cf tanks would be less than a single 125, or if I'm just really overthinking it. Would love any insight from all you welders out there!

Thanks!

I don't know how much welding you intend to do but I would think that one 80 CF would be fine

I would ask the supplier you plan to swap with what they charge to swap each size.

A lot of places charge approx the same amount for an 80 vs 125, so you'd be paying more up front and down the road with 80cfg tanks. If its less than I'd probably go with the 80 cfg tanks. You'd be supporting the supplier and they'd remember you and likely give you a better price on gas down the road.

Also you can break down your cost per hour.

80cf at 30 cfh would give you 2.6 hours tank.
125cf at 30 cfg would give you 4.2 hours per tank.

Then you can calculate roughly your hourly cost per bottle.

For my tig bottle.

125 cfh at 15 cfh ~ 8.4 hours per tank. 80 bucks a tank when I filled it up a year ago, means its about $10 per hour.

I'd go 2 bottle route. It allows either a full spare, or a separate mix to be carried about (75/25 or 100% O2). I have an 80 I use for mobility. I can get a lot more than 2.5 hours out of it, even on MIG.

Not what you asked, but I would also consider a 20 lb CO2 tank. It's about the same size as an 80 cu ft tank but the aluminum CO2 tanks are much lighter. A 20 lb CO2 tank holds 178 cubic feet of gas, and is anywhere from 1/4 to 1/2 the price of a C25 refill. If you are doing mobile work, the weld quality difference between CO2 and C25 is negligible to none. That is going to be a much better answer for mobile work. Plus lots of gas shielded flux core runs fine on CO2, and CO2 gives your MIG gun a higher duty cycle due to better cooling than C25

Oh, and CO2 tanks can be had for $100 or less.

I almost bought the 125 off Amazon but a quick call to my LWS found I was able to get an 80 for way less, got my face known, and supported my local guy.

If you do a lot of welding, I would buy 2 80s so if you're in the middle of a job and the tank runs dry you can swap it out and finish the job.

This is one of those questions that's almost impossible for someone to answer for you. Will your LWS even fill a bottle you bought somewhere else? Will they fill a 125? Some places won't sell individuals bigger bottles, but might lease them...that sort of thing. It really just depends on the shops around you more than anything.

I like having multiple tanks so that when one gets low you can switch to the other and not have as much pressure to get the first one swapped. If you have just one tank, when it gets low you don't have the option of waiting a day or two until it's more convenient.

Generally speaking, the bigger the bottle the lower the cost per CF of gas. It only costs me around $20 more to get a 300 filled than it would be for a 125....so all but one of my bottles are 300s. I keep an 80 for mobility (rarely do that) or if I want to set up a machine in my basement (TIG).

Definitely look into what your LWS charges to fill/swap an 80cf tank vs a 125cf. It's not unusual for an 80cf to cost like $30 while a 125cf might be $35. So you could be paying $60 for 160cf of gas as opposed to $35 for 125cf of gas. If you're doing a lot of welding the price difference would add up fast.

Personally I would probably advise getting a single 125cf or 80cf cylinder and then a 20lb Co2 cylinder if you can find one reasonable cheap. If I'm remembering correctly a 20lb Co2 cylinder holds around 175CF of gas, and Co2 is dirt cheap.

Although I personally don't think it's as noticeable as on tig, things will start to get a little squirrely flow wise once you hit the 200-500PSI range. So if getting both a 75/25 bottle and a Co2 tank is out of the question I would suggest getting a single 125CF bottle and If you find you're running low fairly often then saving up for a second 125cf tank. It will be a lot more efficient in the long run.