Degreasing a fuel tank

Would like to use a 275 gal fuel tank as a catch basin for rain water off roof. Is there a commercial grade degreaser that would work keeping in mind I'm using the rain water for my garden.I have been using food grade 55 gal barrels for this but this year I doubled the size of my garden and need more holding capacity.

Thats going to be a toughie.
I am thinking any degreaser industrial enough to clean the fuel out, can't be any better for ya with the residue it will leave.
Unless you can get something like brake cleaner in a drum. It cleans then evaporates. Good luck on this project.

If a degreaser won't work I have another project that I'm going to use this tank for. A secondary burn chamber for my shop stove. Might work, might not but I'm gonna try.

I was going to use one for a trash burner, and try and incorporate a secondary burn chamber inside at top back. But, the OL decided to pay for trash hauling service, so I don't burn much bu cardboard shipping boxes now.
They also make great smokers, but first you would have to carefully burn the crap that is in it out first.

Why not burn the heck out of it, power wash it, and use if for rain?

I would think a heavy duty steam cleaning and then wash with detergent.
Ed

I pulled the suction tube and plugs out today. It was dry. No fuel. But there was an awful lot of residue kinda like burnt on grease on the tube. I think I'm gonna use this for a burn chamber on the shop stove. Thanks for the ideas though. I was kinda afraid whatever I cleaned it with might be as bad for the garden as the fuel. I don't feel like sacrificing the garden especially this year.

My giant pumpkins only get the best, when it hails I call the wife and tell her to throw the twin boys on top of 'em. Joking....kind of at least! I'm doing the 55 gal barrel string tied to the gutters with an ac clear water pump, works good so far for the last year or two. How big is the garden Lee?

Exactly, do a small controlled burn and then wash it out(rinse/swish/whatever) with Dawn dishwashing liquid. Maybe a half a bottle and clean it that way. I have a 65ft truck and have found that Dawn kicks azz. The best degreaser out there. And isn't harmful to your garden

Dawn is a great degreaser however, it will never get it all out. I'll venture a guess that you will get your share of iron supplement from all the rust in the water over time. Do yourself a favor, find a good large non-contaminated poly tank and save the hassle and your health. Sorry to be devil's advocate.

Do a search - a while back there were some posts on someone that was giving away, or selling for short bucks plastic tanks that were on skids - I think 2-300 gallons each. They had been used as raw stock containers by some plastics company IIRC, but were safe to use for this kind of application, they were being used for water capture and garden irrigation by the user that was talking about them...

Gooserider

How about just tap the water out a little above the bottom to avoid the gunk down there, and the oil residue will float on top, out of your way, killing mosquito larvae until it evaporates.
If the water still is too rank just use it on the lawn until it clears up with time. There will not be any particularly toxic materials in the tank, just fuel oil residue, dirt and rust. Avoid spraying it on edible parts of your plants and you should be okay. Small amounts of fuel oil are soon biodegraded.

Might wanna try this http://www.parish-supply.com/automated_cleaner_degreaser.htm