If you're building an offset out of a used propane tank, the tank is your first big buy.
Here's what I'd tell you before you hand anybody money for one.
Buy it already purged with the valves out. Size it by grate area, not gallons. Look for 3/16" wall or heavier. A rough, pitted tank cleans up. A tank that isn't purged is the one you walk away from.
This page gets you to the point where the tank is home, purged, with the valves out. From there, the build order picks up here: How to Build a Smoker: The Build Order, Start to Finish.
Where to find a used propane tank
A tank refurbisher or a propane company is probably your safest bet.
The tank shows up already purged with the valves taken out. That's the whole reason to go that route. The dangerous part is already done for you.
If you find one somewhere else, figure it's not purged and the valves are still in it. That puts you right back in the next section.
More on finding one: How to Find A Propane Tank for Your StickBurner Build and Where can I buy a used propane tank for building a homemade smoker?
Check #1: purged, with the valves out
This is the check that matters most.
The tank in that picture still has its valves in. That's not ready to buy for a smoker.
Look where the valve was. It should be an open hole. If the seller can't tell you it's been purged and the valves are out, walk away.
A couple of things to know about why:
- The gauge doesn't tell you what you think. The gauge on a propane tank shows how full it is of liquid. It doesn't show pressure. A reading near zero does not mean the tank has no pressure in it.
- It's not just the propane. Even with no pressure left, there can be mercaptan sitting in the bottom of the tank as a liquid, with propane vapor still mixed into it. The heat from cutting makes that mercaptan and propane vaporize fast, and it flashes off. If the tank doesn't have a big enough opening in it, it could rupture, depending on how much is sitting in there.
If purging a tank scares you, don't do it. Buy one that's already done. If you want to see how I do it, watch these instead of reading steps off a page:
Hauling it home
Hauling a tank with the valves still in it under pressure is illegal here in the US. That's hazmat.
The tank will need to be open and purged before you can legally transport it.
Buy it already purged with the valves out, and the hazmat problem never applies to you.
What size tank to buy
Gallons don't feed people.
Most guys shop by gallons. A 250, a 500… bigger must mean more food. That's the wrong number for that question.
Grate area is what tells you how much meat fits. Take the square inches of grate, divide by 144, and that's square feet. Figure about one pork butt per square foot. Gallons still matter, they're what the firebox and stack get sized to. They just don't tell you how many people you can feed.
Weight determines the axle. The axle gets decided the day you buy the steel.
- 250 gallon: a 3,500 lb single axle
- 500 gallon: I'd never put a 500 on anything smaller than a 6,000 lb axle
- 1,000 gallon: a 10,000 lb axle or heavier
So before you buy, put a tape on it. Length, and diameter.
Wall thickness to buy
A tank in the 3/16" to 1/4" range is where you want to be. 3/16" or heavier is a good buy.
Air and water tanks usually run about 1/8". They'll work. They lose heat quickly in the rain.
Here's the honest part. You usually can't measure the exact wall on a tank sitting in somebody's yard. Even I can only guess at it by eye. So you buy by the kind of tank it is, not by measuring the wall at the sale.
Thicker isn't automatically better either. In my experience a 5/8" pit doesn't cook any better than a well-built 1/4" one.
Hemispherical or elliptical heads
Look at the ends. A hemispherical head is a deep half circle. An elliptical head is shallower.
Neither one is a reason to pass on a tank. It changes how far in from the end your cuts land when you lay it out, so just know which one you're buying.
Rust, pitting and dents
Surface rust and pitting are cleanup, not a dealbreaker. I've built on a rough, pitted car wash tank that needed a lot of cleanup.
Every tank also has bungs and fittings on it. Those get cut and plugged during the build, not when you buy it.
What to walk away from
A tank that isn't purged, or still has its valves in and pressure in it.
You can't legally haul it, and the residue hazard is real. Pass on it and buy one that's already purged with the valves out.
Where to go from here
Once the tank is home, here's the order I build it in: How to Build a Smoker. And if you haven't picked a design yet, start here: Smoker Designs.
If this is your first build, you can follow a full 500 gallon build inside SmokerBuilderU step by step, and bring your tank questions to the live Q&A every Wednesday night at 7pm Central.
Join SmokerBuilderU
If you already know your tank size, every plan set I've drawn is at smokerplans.net, laid out by tank dimensions. Fully dimensioned, ready to download.
Browse smoker plans
PS. Put a tape on it before you pay. Length and diameter.
Questions builders ask
Where can I buy a used propane tank for a smoker?
A tank refurbisher or a propane company is probably your safest bet. The tank shows up already purged with the valves taken out.
Is it legal to haul an old propane tank?
In the US, hauling a tank with the valves still in it under pressure is illegal. That's hazmat. The tank needs to be open and purged before you can legally transport it.
What size propane tank do I need for a smoker?
Size it by grate area, not gallons. Square inches of grate divided by 144 is square feet, and figure about one pork butt per square foot. Then check the axle: a 250 gallon on a 3,500 lb single axle, a 500 on 6,000 lb or more, a 1,000 on 10,000 lb or more.
How thick should a propane tank be for a smoker?
3/16" to 1/4". A tank that's 3/16" or heavier is a good buy. Air and water tanks around 1/8" work but lose heat quickly in the rain.
Is a rusty propane tank OK for a smoker?
Surface rust and pitting are cleanup, not a dealbreaker. The tank to walk away from is one that isn't purged or still has its valves in.
