diesel fuel... what do you do?
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condensation theory
Not sure if the theory has ever been proven but alot has been written about what is best to avoid condensation in the tank. Conventional wisdom is to fill or at least partially fill it - an empty tank can allow more condensation to form. It's pretty simple to either drain or pump a small sample from the bottom come spring time to ensure little or no water has colleted. Just make sure your fill pipe cap has a good seal.
Not sure if the theory has ever been proven but alot has been written about what is best to avoid condensation in the tank. Conventional wisdom is to fill or at least partially fill it - an empty tank can allow more condensation to form. It's pretty simple to either drain or pump a small sample from the bottom come spring time to ensure little or no water has colleted. Just make sure your fill pipe cap has a good seal.
I find these discussions about diesel fuel storage
intriguing. About half of the homes in north america are heated with number 2 fuel oil, aka diesel fuel. many of the storage tanks are outside of the buildings they supply and there is never any problem with condensate of contamination of the fuel. There is always a fuel filter installed close to the oil burner and there is a jet that atomizes the fuel going into the combustion chamber. All of these supply tanks draw the fuel from the bottom of the tank so that if any water was present it would interfer with the fire and the operation of the oil burner. The tanks are generally 275 gallons and are refilled about once a month. I am beginning to believe that the source of water in diesel fuel tanks on boats has an origin other than condensate, such as a leak at the filler cap.
intriguing. About half of the homes in north america are heated with number 2 fuel oil, aka diesel fuel. many of the storage tanks are outside of the buildings they supply and there is never any problem with condensate of contamination of the fuel. There is always a fuel filter installed close to the oil burner and there is a jet that atomizes the fuel going into the combustion chamber. All of these supply tanks draw the fuel from the bottom of the tank so that if any water was present it would interfer with the fire and the operation of the oil burner. The tanks are generally 275 gallons and are refilled about once a month. I am beginning to believe that the source of water in diesel fuel tanks on boats has an origin other than condensate, such as a leak at the filler cap.
Condensation in diesel tanks
Like you, Ross, I too wonder. We brought our boat 5 years ago and I syphoned all the fuel out at that time- not much- 5 gal or so- as I did not know what the conditioon of the tank was. I found no water in it- no idea of how long since the tank had been empty. A year ago I cut an opening port and thorughly leaned the inside. Lots of gunk- probably about 23 years worth- the boat is an 83. I filtered the fuel back in through a WM funnel filter and again found no trace of water. This is a climate that has temperatures from 90 F to -10F and very high humidity in the summer. Sounds ideal for condensation. I wonder if condesation really is the problem it is said to be- I dont remember my farming relatives making much fuss about it.
Like you, Ross, I too wonder. We brought our boat 5 years ago and I syphoned all the fuel out at that time- not much- 5 gal or so- as I did not know what the conditioon of the tank was. I found no water in it- no idea of how long since the tank had been empty. A year ago I cut an opening port and thorughly leaned the inside. Lots of gunk- probably about 23 years worth- the boat is an 83. I filtered the fuel back in through a WM funnel filter and again found no trace of water. This is a climate that has temperatures from 90 F to -10F and very high humidity in the summer. Sounds ideal for condensation. I wonder if condesation really is the problem it is said to be- I dont remember my farming relatives making much fuss about it.
Condensation Questioned
I'm siding with the non-condensation group, as we have a polyethelene tank and I believe the fuel and tank are always at nearly the same temperature and that the winter temperatures dont hold much moisture. I no longer top off the tank and I don't drain it. Aparently low sulfur diesel dosen't age well and I'd rather add fresh fuel in the spring and keep only as much on board as I reasonably expect to use. I also added an inspection port and found that the pick-up tube is 1/2" or more above the bottom witha 45 degree forward facing bottom edge. The access opening allowed me to completely clean the bottom and al sides of the tank. I'll keep an eye on the 'O' ring on the deck filler cap as that can typically be the biggest single source of water intrusion.
I'm siding with the non-condensation group, as we have a polyethelene tank and I believe the fuel and tank are always at nearly the same temperature and that the winter temperatures dont hold much moisture. I no longer top off the tank and I don't drain it. Aparently low sulfur diesel dosen't age well and I'd rather add fresh fuel in the spring and keep only as much on board as I reasonably expect to use. I also added an inspection port and found that the pick-up tube is 1/2" or more above the bottom witha 45 degree forward facing bottom edge. The access opening allowed me to completely clean the bottom and al sides of the tank. I'll keep an eye on the 'O' ring on the deck filler cap as that can typically be the biggest single source of water intrusion.
Condensation experiment
The worst thing about this recurring thread is that it is a good indication of the approaching end of the season. I think this winter I will try an experiment. I'll seal bucket and add a vent hose of about the proper size, maybe one with a little fuel, another empty, both plastic and metal for a total of four buckets. Then I'll see if the condensation that is frequently visible on all exterior surfaces occurs inside the tank too. Surely somebody has done this in the past.
The worst thing about this recurring thread is that it is a good indication of the approaching end of the season. I think this winter I will try an experiment. I'll seal bucket and add a vent hose of about the proper size, maybe one with a little fuel, another empty, both plastic and metal for a total of four buckets. Then I'll see if the condensation that is frequently visible on all exterior surfaces occurs inside the tank too. Surely somebody has done this in the past.
Inside a bucket different than outside a bucket!!!
My car gets covered with dew because of radiational night time cooling. The outside surface is exposed toa virtually unlimited amount of cool humid air. You may have noticed that the inside of your car doesn't get covered with dew. Because there is a limited amount of air in your car and that small amount of air in a car does'nt hold much water. The same thing happens in our fuel tanks!!! Even with extreme temperature changes the volume of air moving from outside the tank to inside the tank is small. With gasoline the effect is much greater because gas vaporises when it is warm and condenses when it is colder. It is prossibly a good idea to keep a gasoline fuel tank full unless you have a valve in your vent line. I guess a valve in the vent line of a diesel tank would also reduce the exchange of air. The valve allows air in to relieve a vacum but stops air from leaving resulting in a small pressure increase when the tank is warm.
My car gets covered with dew because of radiational night time cooling. The outside surface is exposed toa virtually unlimited amount of cool humid air. You may have noticed that the inside of your car doesn't get covered with dew. Because there is a limited amount of air in your car and that small amount of air in a car does'nt hold much water. The same thing happens in our fuel tanks!!! Even with extreme temperature changes the volume of air moving from outside the tank to inside the tank is small. With gasoline the effect is much greater because gas vaporises when it is warm and condenses when it is colder. It is prossibly a good idea to keep a gasoline fuel tank full unless you have a valve in your vent line. I guess a valve in the vent line of a diesel tank would also reduce the exchange of air. The valve allows air in to relieve a vacum but stops air from leaving resulting in a small pressure increase when the tank is warm.
Diesel fuel
Actually only about 15% of homes in the U.S. use oil for heating fuel, and they are primarily in the northeast. The bulk of U.S. home heating is with natural gas. That being said, and having a lot of experience with diesel fueled vehicles of one sort or another, I definitely side with the idea of emptying and refilling, if just to have fresh fuel in the spring. Using Stabil with the amount remaining in the tank will help also. Maintain your water-separating fuel filters and you should never have a problem.
Actually only about 15% of homes in the U.S. use oil for heating fuel, and they are primarily in the northeast. The bulk of U.S. home heating is with natural gas. That being said, and having a lot of experience with diesel fueled vehicles of one sort or another, I definitely side with the idea of emptying and refilling, if just to have fresh fuel in the spring. Using Stabil with the amount remaining in the tank will help also. Maintain your water-separating fuel filters and you should never have a problem.
To me, you've got to do
..whatever it is that works for you. In my case, I keep my fuel tank nearly full almost all of the time (I'm only talking about an 11.5 gal tank anyway). I refill the tank whenever I've used about 2 gal of fuel and use a jerry jug full of the freshest fuel I can find (busy local truck stop). I filter the fuel through a WM water/crud separating filter, add a bit of biocide, Pri-D, and cetane booster each time. I'll do this at the end of this season, too. I replace the primary filter each spring, and the secondary about every 3 yrs. I don't know what the average age of the fuel in my tank is, but am guessing it is younger than if I ran the whole season on the same tank I began the season with. To date, I have never had any fuel related engine problems, so this is a system that works for me. Find out what works for you and use that.
..whatever it is that works for you. In my case, I keep my fuel tank nearly full almost all of the time (I'm only talking about an 11.5 gal tank anyway). I refill the tank whenever I've used about 2 gal of fuel and use a jerry jug full of the freshest fuel I can find (busy local truck stop). I filter the fuel through a WM water/crud separating filter, add a bit of biocide, Pri-D, and cetane booster each time. I'll do this at the end of this season, too. I replace the primary filter each spring, and the secondary about every 3 yrs. I don't know what the average age of the fuel in my tank is, but am guessing it is younger than if I ran the whole season on the same tank I began the season with. To date, I have never had any fuel related engine problems, so this is a system that works for me. Find out what works for you and use that.
I had water in my diesel tank once.
Horrible problem. I was in Costa Rica at anchor. I was filling the tank with a jerry can and doing work elsewhere when a tropical downpour slammed the boat. It was amazing. Solid water in the air. Couldn't see the ends of the boat! Then I remembered the fill cap and jerry can. Water was entering the tank-fill like a bathtub draining. The rest of the story is ugly. I'll save that for another time. As far as any other water in my two diesel tanks; nope, nada, not a drop in over 20 years, northwest U.S. climate or tropical.
Horrible problem. I was in Costa Rica at anchor. I was filling the tank with a jerry can and doing work elsewhere when a tropical downpour slammed the boat. It was amazing. Solid water in the air. Couldn't see the ends of the boat! Then I remembered the fill cap and jerry can. Water was entering the tank-fill like a bathtub draining. The rest of the story is ugly. I'll save that for another time. As far as any other water in my two diesel tanks; nope, nada, not a drop in over 20 years, northwest U.S. climate or tropical.
car anology
Not sure how appropriate the analogy to a car's gas tank is given the system (on a contemporary car) is not vented and it is gas vs. diesel. Regardless of what one chooses, it's a good idea to check the contents of the tank in the spring.
Not sure how appropriate the analogy to a car's gas tank is given the system (on a contemporary car) is not vented and it is gas vs. diesel. Regardless of what one chooses, it's a good idea to check the contents of the tank in the spring.
Don , There has to be some sort of a vent
on an automobile fuel tank or you couldn't pump gas out of it without collapsing the tank. Back in the dark ages before pollution controls a little water in a gas line would freeze in the winter and stop the car dead. As soon as the air got above freezing the car would run normally. We used to add a little alcohol to the tank to absorb the water and send it through the system and burn it with the rest of the gas.
on an automobile fuel tank or you couldn't pump gas out of it without collapsing the tank. Back in the dark ages before pollution controls a little water in a gas line would freeze in the winter and stop the car dead. As soon as the air got above freezing the car would run normally. We used to add a little alcohol to the tank to absorb the water and send it through the system and burn it with the rest of the gas.
Not positive Ross
The reason you mention (pressurization while filling) or creating a vacuum while running is certainly true, however, when idle such as a boat during winter, no circulation can occur because of emission controls on automobiles which allow air in only while running and allow air out through the fuel pump nozzle only while fueling. Didn't know I could write a sentence that long... This subject arises every year with no consensus which I take to mean everybody is right
The reason you mention (pressurization while filling) or creating a vacuum while running is certainly true, however, when idle such as a boat during winter, no circulation can occur because of emission controls on automobiles which allow air in only while running and allow air out through the fuel pump nozzle only while fueling. Didn't know I could write a sentence that long... This subject arises every year with no consensus which I take to mean everybody is right
vent in fuel cap
Most vehicles have a vent built into the filler cap. It has a valve to let air in but won't let gasoline vapors out. Gasoline is so volatile that a simple vent tube would allow a lot of evaporation.
Most vehicles have a vent built into the filler cap. It has a valve to let air in but won't let gasoline vapors out. Gasoline is so volatile that a simple vent tube would allow a lot of evaporation.
Ross...
...Please remember that Home Burners will practically burn anything. That is why there are little problem with them. Also, automobiles (earlier vintages) always vented at the gas cap. That's why they had no collapsing of tanks. New cars also have the cap vented, albeit a bit different that earlier cars.
...Please remember that Home Burners will practically burn anything. That is why there are little problem with them. Also, automobiles (earlier vintages) always vented at the gas cap. That's why they had no collapsing of tanks. New cars also have the cap vented, albeit a bit different that earlier cars.
Tank
Top the tank and ad a biocide and Sta-Bil. That's why airplanes, especially those that are kept outside, are always topped off...keep the water out.
Top the tank and ad a biocide and Sta-Bil. That's why airplanes, especially those that are kept outside, are always topped off...keep the water out.
Car analogy
Moonsailor was referring to the cabin of your car, not the fuel tank. I have wondered about that. It's a great question. So if you leave your windows cracked open an inch or two, you should get condensation all over the inside of your car too.
Moonsailor was referring to the cabin of your car, not the fuel tank. I have wondered about that. It's a great question. So if you leave your windows cracked open an inch or two, you should get condensation all over the inside of your car too.
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