Should I vent diesel storage

[Coyote machine]

I've got a 300 gallon gas tank on skids that I cleaned out and put a new plastic suction pipe in the end that has a metered gas pump on it. The tank is vented to the outside of the building year round via an iron pipe of around 2" diameter, with a cap to keep water from getting in.. This tank is stored indoors in my heated barn, and I had it spray foamed when I was doing my barn's walls. I use two filter's on the outlet pipe after the pump; one is a TSC fuel filter, and the other is a fuel water separator. I mark both for date and # of gallons so I know when to change them out. I buy ONLY winterized fuel due to my climate, and do not add any additives to the mix beyond the fuel being winterized already prior to delivery. I've never had a fuel issue since 2009, and probably 900 or more gallons to date.
I'd check the gallons used on the meter but I'm 5,083 miles away in the Turks and Caicos!

 

[TractorGuy]

I decided to just leave the caps loose for now. I ordered a pair of compressor filter/mufflers that were advertised as 3/4 but they were 1/2" npt. I might get some bushings and use those but I like the radiator cap idea.

The pickup tube to supply my genset is a few inches from the bottom like any other fuel pickup should be. I will pump some off the bottom periodically to check for water.

Had a 5 gal oil can with some diesel in my garage and discovered today it split the top seal from expansion. Leaving fuel in a container that can't vent seems to be a bad idea.

 

[DaveK OR]

I ordered a pair of compressor filter/mufflers that were advertised as 3/4 but they were 1/2" npt.

I'll take a wild guess and say that they used the thread-diameter as their sizing, instead of the NPT spec. I've run into that with hydraulic systems, as well, with 1/2" JIC (more properly JIC-8) being called 3/4" JIC.

 

[TractorGuy]

I thought I would do an update on this. I decided to leave the bungs loose to allow fuel to expand and contract. Drums were filled January 2nd. I pulled about 30 gallons out of one a couple of months ago. Emptied it today and took a few gallons out of the other drum. Before I started today I took a sample off the bottom of both drums and have no water or sludge. When drums were filled I added an once of Killem Biocide in each one and half a bottle of Stanadyne lubricity formula.

 

[fried1765]

I thought I would do an update on this. I decided to leave the bungs loose to allow fuel to expand and contract. Drums were filled January 2nd. I pulled about 30 gallons out of one a couple of months ago. Emptied it today and took a few gallons out of the other drum. Before I started today I took a sample off the bottom of both drums and have no water or sludge. When drums were filled I added an once of Killem Biocide in each one and half a bottle of Stanadyne lubricity formula.

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I wonder if that is what they do to store their diesel in Bangladesh?

 

[Raspy]

A common problem with diesel powered boats is condensation in the tanks that leads to algae buildup. I had that problem on my sailboat with two 50 gallon tanks that were always vented.

Out in the high desert with lower humidity, it might not be as much of a problem. I have two 300 gallon fuel tanks for my oil boiler that show no signs of any water or algae after just two years of sitting with open vents.

I also have six 55 gallon drums full of stored fuel for heating later. They are all tightly sealed. No problem with them either. They will build up some pressure but they are designed to deal with it. A nice idea is to paint them white or keep them out of the sun, but it's not necessary.

One other problem is if they are upright and collect water around the bungs, where the tank seal can be higher than the bung opening. Or have melting snow sitting on them. Be sure to have them absolutely tight and sealed or the water will get in when they cool. I used steel bungs and wrapped teflon tape over the top of the o-rings before I installed them.