I'm looking to buy a 200 to 350 gallon elevated, gravity feed fuel tank to store non-oxy gas for saws, generator, mowers, Polaris Ranger, etc., with the thought of (infrequently) using it for daily driver fuel to keep it rotated. Been planning to do this long before the pipeline issue, now we just live in a rural enough area with a big enough property that we can make it work.

Looking online for used tanks, what do I need to watch for? I don't mind sanding and painting, replacing the hose/handle/fittings, and other cosmetic things, but what's a deal breaker? Holes, obviously, but how do I check for small leaks? I'm assuming a welder could repair small pinholes but would I have to test with water then drain and dry before filling with gas if it needs to be welded?
What about the interior? Is a little rust a no-go?
Any information would be appreciated.

Elevated = target, keep that in mind.

I did not want to go elevated, i wanted my tanks under roof and out of sight, and as low as possible.  I have electric pumps installed now, with 1 rotating and 2 lever style manual pumps for backup in case electric becomes unreliable.  Under roof to help prevent condensation and water infiltration.  Out of sight because I value my privacy and have no desire to have my tanks visible from distance or air.

As far as acquiring a tank, farm sales, fuel dealers (who is going to fill your tank - check with them).  I have some from auctions and some from a local tank dealer.

A failure with a fitting on a gravity feed system can make for a really bad day. I personally wouldn’t have gravity feed.

So for those saying ground-mounted: do they make reliable 12v pumps? Because this thing is going in a very secluded area of my property, under heavy tree canopy, and nowhere near electricity.
I'm not against ground-mounted, but I can't afford new in either instance and  want to know what to look for in used, regardless of which style I buy.

Hand pump...

If you are using a 12 volt system, a solar panel might give you what you are looking for in power.  This would also give you the option to run a set of cheap LED lighting for the building.

A good hand pump might be the best solution for fuel transfer.  I would still have the tank raised a bit (inches) to prevent contact to the ground (rust).  But 300+ gal sure weights a lot so that might not be a good idea.

A small setup of 100 gal system you might want to look at boat fuel tanks.   Another option is heating oil tank and you will see some options from Lowes / Home Depot.

So just how are you going to fill up that tank?   You might need a smaller tank to fill up at the gas station and then transfer pump that to the holding tank.  

Not sure about bulk fuel storage and such laws, so there can be issues with that from insurance to other regulations.  

Farm supply places might be another good location for supplies / info.

If you run it off 12 volts, you should have a source for 12 volts handy at all times.....the vehicle or equipment you are filling. Just make sure the wires to the pump are long enough.

In my area, lots of farmers have fuel storage and the raised fuel tanks are the most common. I can see the concerns of a raised fuel tank leak but if you have a leak in a ground level tank, it's all going to leak out too. A reliable shut off at the tank and maybe a second shutoff for redundancy (and then USE it) should be part of your plan. Also, raised tanks need some protection from vehicles and/or tractors running into them (and knocking them down....not a good day) so take that into consideration as well.

I use a Holley electric fuel pump and a 12v battery to move fuel.  It isn't that fast, but it does what I need.  Filter on the input and output.  The entire unit is mounted in an old orange Homey D toolbox.  The pump is the blue pump which is supposed to be 120Gph.

This is an earlier design, I use a smaller battery now and another filter.  Securing the battery is a good idea if you move it around with the battery installed.

I have a smaller 275 gallon tank set up with a 12 volt pump and a marine battery.  We use this tank to take out for field work.  It is light enough when full that it is easy to lift with a machine and set on a farm trailer.  We built a skid for it to set on so we can drag or lift by the skid and not the tank.  This tank is for fuel transfer out in the field, or for situations where we need limited fuel at another location.  We also use it for filling other tanks at remote locations that a fuel truck can not get to certain times of the year.  I keep a trickle charger on the battery, when it is in the storage shed on the farm, but I think a solar charger would also work fine if it was away from power.  I would still have it under cover of some sort.

In your situation, I would probably look into a good quality hand lever or rotary pump if this would be for limited use.  Fill-Rite would be a good brand to look at, but that brand will cost more than the Chinese copy of it.

Yes, they make reliable 12V pumps, and they also make hand crank pumps. FillRite or GPI both are excellent brand 12V pumps. Cut off a section of jumper cable and wire it into the pump so you can power the pump from the vehicle you're filling. This is very common on construction sites. You can also build up a solar powered battery system and use the jumper cables as backup. Keep the tank in a well-ventilated place so you don't risk igniting any gas fumes. Diesel won't have ignitable fumes.

If you buy an old heating oil tank, make sure it has at least two bungs on the top. Many kerosene tanks only had one, because they were gravity fed. You'll need one for fill cap, and one for the pump. If you are storing gasoline, you need a vent, too. You don't need a vent for diesel/kerosene. If you only have two bungs, you can use a wye fitting to incorporate a vent and a fill port in the same bung, but you'll have to be careful not to overfill (heat can cause expansion = spillover). Three or more bungs is best, but these tanks are harder to find. If you've got extra

All tanks will have a drain plug at the bottom. I'd recommend against gravity feed for a different reason: water. Petroleum floats on water, which means water settles to the bottom of a tank. The drain plug that often is used for gravity feed will let that water get into your engine. Water can come from an improperly doped fitting, from condensation, from ethanol gas breaking down, or very rarely from bad gas at the pump/delivery.

I'd look for heating oil tanks being given away. Pay as little as possible. There's bound to be some "haul it off and you can have it" deals in your area. Once you get it, dope off all the fittings and then stuff an air hose wrapped in a wet rag in the drain plug, and pressurize the tank. This will help you find any leaks. If there's a leak, scrap the tank and start over.

Use Gasoila brand pipe dope, it's petroleum resistant.

I'll add more if I think of it.

I agree with those that say install a ground tank and put a pump on it.  I have this GPI hand lever pump that works surprisingly well.  I've replaced it with a Fil-Rite 120 vac pump on my diesel tank, so I'll be putting the GPI pump on my new fuel transfer tank that I'm getting.

About $200 from JMESales or Amazon; cheaper if you find them already attached to some farm tank off of CL or FB.

The problem right now is that everyone has the same idea you have and the pickings on CL can be few and far between.  

Bought an old shabby looking 300 gal with 6' stand at a farm auction. I think it was about $80.
Wire brushed it, painted it JD green (mistake, should have kept it reflective silver), bought a new valve with filter/water trap and new hose/nozzle. Still had under $200 invested, back in the 1980s.
Used it about 15-20 years with no issues. Replaced the hose once in that time. Kept a padlock on the valve, never had gas stolen from the tank, but did have my pickup siphoned once when it was parked within sight of the big tank (which had diesel in it by then, I almost wouldn't have minded the crooks filling their car with that). Fuckers stole or threw away my gas cap when they siphoned me, so I put locking caps on everything when I bought a new cap for the truck. PITA sometimes getting it unlocked at gas stations, but never got siphoned again.

For overhead ask your gas supplier. They may give or lease you a tank for buying gas through them.

For an on ground tank tractor supply has 12 volt fuel pumps.

Another option is to find an old propane tank. Decommissioned tanks are available at propane supply companies. They will usually damage a fitting so it can't be used for propane any more, but you can have a welder put new fittings to convert it to store gasoline.

You need a dip leg to attach your hose to and a way to fill the tank. Make sure to put valves on all fittings so you can pressurize the tank. 5 psi of propane will make it a long term storage option. Under pressure the gasoline will not boil off the light fractions, keeping it fresh for as long as you need.

Propane tanks are rated for 225 psi service so 5 psi is nothing to the tank. I've seen this done at a propane supplier for their forklift gas. On a sunny day the heat of the sun will build pressure. They use gas fast enough they don't worry about it spoiling.

Cannot comment on where to purchase used tanks but I do agree with not getting gravity feed tanks.  

If you must get a gravity feed tnak make sure the first connection is to a good quality shutoff valve so if any hardware fails you can easily stop the environmental police from visiting you.

Bill

I have a 275 gallon tank that I got brand new.... but I got mine from my buddy who sells them and it was half price.

The same guy also sells barrels of non-eth gas... he is a fuel supplier.

steel barrels are perfectly fine to store gas in and that is the route i would take if I had to pay retail.   rotary hand pumps work well.

keep them in a shed.

Thanks for all the info.

@OverScoped

For steel barrels, would a quality pallet work for the storage platform?  I’m getting pallet forks for my tractor so I could put it into my truck or on my trailer to refill it.

The problem is it's not real stable when you start moving it around with forks.
I would definitely use ratchet straps to secure it's on the  pallet before I moved it.