I set up a 110 gallon fuel transport tank late last fall, filled to about 100-105 gallons, treated with Stabil, etc.

The filler cap is a "vented" cap, with a spring powered valve/gasket thing, that will open if the pressure gets too high, and it is not frozen, it operates under thumb pressure.

The hand nozzle side was alll threaded with plumber's tape, and torqued down tightly.

On inspection last week, there is heavy gas residue spatttered all down the side of the tank on the fill nozzle side, with traces showing leaking fuel at the base of the handpump, and at most other joints along the line, pump/filter fitting, both sides of the bowl/paper/ater filter, both sides of the flow meter, and at the nozzle.

When I pop the filler cap, a healthy burst of over=pressure exits the tank, understandable since the temperature is warming up and expanding the gas since it was filled in November.

Three questions:

1. Is this normal? Are fuel tanks expected to seep fuel as temps rise and fall?

2. Was plumber's tape a bad idea for fuel fittings? The instructions explicitly recommended using it, and didn't specify special tape for use with gasoline.

3. Are there fire or explosion risks here? There is vapor present around the tank, not too bad but you can smell it. The tank is grounded, but I'm uncomfortable even being around it, much less opening it up. It's a bomb and I continually worry that even a small spark will set it off.

Thanks for any help you can give.

the fuel tank should not leak.... does your vehicle gas tank leak????  no..  im blaming most of the problem with the tank being too full......although, if its leaking at ALL the joints, its also most likely the thread sealer was not rated for gasoline..it should be replaced.

the plumbers tape should be good for pressure, we have water pressure at 70 lbs and no leaks. however ,the tape might very well be eaten up by the gasoline.  im doing a fuel storage project, and im going to be using ptf, pfe paste, ( cant remember the exact name), its a thread sealer that says on the tube that its good for acids, and fuels, etc.
         
          it could also be leaking around the vent cap. the fuel level can easily rise when the temps rise, and if it runs out of room for expansion, it will leak everywhere, from being pressurized...... i would keep less fuel in the tank from now on, maybe 95-100 gallons max, and possibly redo the connections with another  thread sealer.  im going to be adding a vent to my tanks, but it will probably be 6-8 feet higher than the tank, to let fumes leave as high from the tank as possible. im going to have a tank in a small out building im building just for my fuel tanks...... good luck......

can't help you with the venting problem but will add that regular teflon thread tape will not stand up to gasoline/diesel etc. They do make a yellow gas tape that should work or you could use a pipe dope paste  or rector seal paste.

That said the absolute best stuff that I have found to seal threads on a fuel system is Permatex #2. It is a form in place gasket material but it works awesome on threads. It cures to a flexible seal. I have used it on my Diesel for both fuel and oil lines and have never had a leak since going to it. The stuff works so well I have started to use it on threads of my house plumbing that ends up behind a wall (like a shower stub out). I had one stub that no matter what I did it had a very slow leak. Used the Permatex and it has not even been moist for the past 7 years.

Get it at any auto parts store and I pretty much gaurentee that if the leak was from a threaded joint that it will not leak after you use the prematex.

Hope this helps

J-

After 20 years in plumbing fuel tanks, this ^ is correct.Ops

Permatex #2...check.

What are the odds that re-sealing five or ten metal threaded joints will pop a spark big enough to ignite fumes and...

fuel vapor for from a vent will make a damp like stain on tanks. Diesel is 10x worse then gasoline when it comes to vent stains

At my job we routinely fill large diesel storage tanks(150 to 500gal). They are all welded steel construction and have open gooseneck style vents. Our rule of thumb is to never fill the tank closer than six inches from the top. I have never seen one of them leak due to pressure build up.