I have an old 150gallon fiberglass tank that I want to get back into operation. I'm tired of having 20 5 gallon jugs laying around. It's not overly large, but it is awkward, and it's just inside the double doors in a shed, and 6' in the air. It hasn't been filled in 20 years, and it is currently empty. Im not sure my bulk fuel guy will fill it due to regulations, but if he can, I would like to clean it out prior to filling.

Are there any cleaners that will dissolve any solids and kind of clean out the inside of the tank a bit? If this was an ATV tank, I'd just take it off and dump some lacquer thinner in and swish it around, but thats going to be tough and expensive.

Any ideas? Or...fill it up, change the filter, full send?

Being old and fiberglass, are you sure it's sound enough to hold that weight? I'm not a fiberglass expert so you guys correct me if needed but if it is in poor shape would the fiberglass pieces clog the fuel injection?

Came here to say denatured alcohol then saw that it's a 150 gallon tank.

S.A. Aggie said:

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Being old and fiberglass, are you sure it's sound enough to hold that weight? I'm not a fiberglass expert so you guys correct me if needed but if it is in poor shape would the fiberglass pieces clog the fuel injection?

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Yeah, it's basically on a framed timber 'shelf'. So, the underside is completely supported continuously everywhere by 2x4 side by side. Good question and catch though.

SanAntoneAg said:

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Came here to say denatured alcohol then saw that it's a 150 gallon tank.

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Lacquer thinner isn't 'that' expensive. Probably a gallon of it poured in the bottom and 'swabbed' around would do the trick. I really need to pull it down if they agree to fill it because I want to make sure the bung seal underneath is totally sound. That would suck to put 100 gallons of gasoline in it and have it drip out the bottom. LOL.

Not a huge deal to keep using gas cans but people give you funny looks when you pull up to the pump, lower the tailgate, and the bed is filled front to back in gas cans and they realize this is going to take a while and they take up a lot of space filled.

I think that's what I'll do. I'm gonna dump some of this purple degreaser **** in it. That stuff will eat the paint off an an engine block. Should do the trick!!

I have cleaned some older 75 & 100 gallon polyurethane marine gas tanks with a solution of Naptha and a couple of gallons of Chem-Tool. I use a 10 gallon 12volt electric pump sprayer to spray the sides best I could....let it soak a bit...then do that three or four times. Then rinse with Naptha.

I have all of that on hand as well. My parts washer uses Naptha. I'm slightly worried that the gas man won't fill it due to some ridiculous law that has changed or they are now following that changed in the last 20 years. LOL.

Might be best to make a call to find out before you put in a lot of time and expensive chemicals?

Will foberglass stand up to gas?

Fiberglass will deposit in engine cylinders and cause failure. Through it away.

Its not the fiberglass fibers that is the issue but the resin used to bond the fiberglass, and if gelcoat was used over the resin. Depending on the brand of resin used it is usually not permeable by gasoline. Even more so if the resin has gelcoat on it. Fiberglass boats, if constructed correctly with a quality resin and gelcoat, have to be impermeable to fuels.

Good explanation. I'm skeptical a decades old tank that's been in a barn has a good finish on the inside. Or if it ever did, seems unlikely to still be intact

I agree. We sure don't build any of our gas tanks in the boats out of fiberglass.

I would be very hesitant to try an old fiberglass tank. Just go buy one of these and call it good.

https://a.co/d/0guXhHqf

Gunny456 said:

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I agree. We sure don't build any of our gas tanks in the boats out of fiberglass.

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Yes, I imagine for boats this is a poor choice since they will shatter and basically explode if they crash. This is why they were phased out of motorcycle use, but in the 60's-70's they were pretty popular. These were popular and very good for underground tanks and stationary applications since they don't rust. They stopped using them due to safety concerns and with upgraded regs for underground tanks, they were phased out of that too.

I was told this was for gasoline for decades, but the liquid in the bottom now is definitely some sort of fuel oil and the fact of the matter here is that there is no telling what the tank is or what or where it came from. This ranch is over 150 years old and if I told you things were thrown away and not repurposed for everything necessary….that would be a dang lie. Nothing was wasted. lol.

Probably best to abandon this idea and use my 250G overhead for gasoline and kick the diesel in it to my 1200G tank.

I am so getting one of these. I can't believe I've been oblivious to their existence until today.