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Go Back   SailNet Community > On Board > Gear & Maintenance > Engines > Diesel > How much water in the fuel filters is Ok?
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Diesel This is a forum dedicated to diesel engines and their applicable accessories.


Thread: How much water in the fuel filters is Ok? Reply to Thread
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Topic Review (Newest First)
10-15-2013 09:32 AM
pdqaltair
Re: How much water in the fuel filters is Ok?

Quote:
Originally Posted by RichH View Post
Think about this .... do empty tanks magically fill with water from condensation? of course not....
I hate to argue with Rick, but in this case he is provably wrong. I have tested this specifically on different scales, from lab to thousands of gallons.

No, an empty tank would not fill with water. When dew falls from the roof it lands on the bottom and evaporate on the next nice day. What happens, however, is that the water falls through the oil and becomes trapped where it cannot evaporate. The process is slow and will not amount to more than an ounce per year, depending on tank size, climate, and the position of the tank in the boat. But an ounce can lead to a lot of corrosion and bio-growth issues.

CAT apparently has seen the same thing (from the link below)
"Water Contamination
Water can get into your fuel if itís mishandled by your fuel supplier. Most often, however, water gets into fuel tanks by condensation from the atmosphere. As the tank empties, air enters the tank. Water condenses on the walls and runs down the sides. The water never evaporates because it's heavier than fuel and goes to the bottom of the tank.
After this process is repeated several times you may have a significant amount of water in the bottom of your tank."

---

No valve; maintaining a clear vent is critical to safety.

---

The greatest risk is almost certainly your own fuel filler cap. In fact, any time there is more than a few ml of water, there has been a leak into the tank, either on the boat or in the distribution chain. But given that fact that, in general, boaters have water problems and truckers do not, suspect condensation.

AVD2 | Air Vent Dryers | Products | H2Out

---

With a 20 gallon tank operated 100 hours/year, old fuel is not a big problem; I would fill the tank. I would tend to agree with Rick if the fuel was going to be kept more than 6 months. Condensation or not, fuel tends to darken and deteriorate over time.
10-15-2013 08:53 AM
arvicola-amphibius
Re: How much water in the fuel filters is Ok?

Conventional wisdom seems to go with keeping your fuel tanks topped off. That has always been my practice and it is not often that I ever get more than about two ml of water out of the glass bowl in about every 10 hours of running.
I have only ever had a bad dose of water in the fuel once in more than 30 years of running diesels in boats. This occurred last year when filling from a dockside pump which had a long, black hose running from the shore-side bowser out about 50 metres to the deep end of the jetty. The hose probably held at least five gallons on its own, and being black, I imagine that it got hot and humid inside. So when I filled, that first five gallons of old diesel in the hose between the pump and the nozzle probably had half a gallon of condensation mixed with it.
Although the glass bowl on the low pressure filter was nearly full of water before I caught it, no water found its way to the high pressure filter on the engine. However, after clearing the water from the tank I did change both the low pressure and high pressure filters just to be safe.
So....some water in the low pressure filter is probably unavoidable and nothing to worry about provided that you have a program to drain it off at regular intervals.
10-08-2013 12:05 AM
miatapaul
Re: How much water in the fuel filters is Ok?

If you are using the same fuel in your car, check the filters in it. It could be that you are getting wet fuel. Are you getting it from a high volume diesel supplier? Some stations don't turn there stock over very quickly and can get a lot of water in there tanks. So stick to truck stops and stations you see a lot of movement at the stinky pump. Marine diesels will drink pretty bad fuel without much complaint as they are relatively robust, but cars are not. For instance VW high pressure pumps can be destroyed by very little moisture and will set you back many thousands of dollars. This is the reason the only way I would buy a VW TDI is if it was new or owned by someone I know and the last new car I bought was in 1990 so I don't like new cars.
10-07-2013 04:21 PM
Ahoyhoy
Re: How much water in the fuel filters is Ok?

Oh my Jesus! No no no!! Why are you saying this? Have i gone mad? What data? What data?!

This is from BP, a fuel manufacture.

http://www.bp.com/liveassets/bp_inte...torage_ADF.pdf

This is from John Deere, engine manufacturer:

Service Miscellaneous

I will even include a link to a letter from some guy who works for a legitimate company, not because he is knowledgable but because some people like official letters.

http://marine.cat.com/cda/files/9492...%20Thought.pdf

A storage tank manufacture:

Diesel | Information On Petrodiesel & Diesel Fuel
01-02-2013 04:27 PM
kellysails
Re: How much water in the fuel filters is Ok?

OK, very different from what I have been told but your opinion is backed with with great data. Great stuff Rich, thanks!
01-02-2013 03:58 PM
RichH
Re: How much water in the fuel filters is Ok?

Quote:
Originally Posted by kellysails View Post
Great thread!



Hmmm, I have always understood that you want the tanks full which reduces in-tank condensation. This is interesting.
Think about this .... do empty tanks magically fill with water from condensation? of course not.

Its the large thermal mass of fuel that leads and lags the 'thermal swing' hence accelerating the 'condensation' ... but this is on a minimal scale. Fuels are made at high temperatures thus are delivered in a 'dehydrated' state ... the water enters (equilibrates) from the atmosphere (through tank vents, etc.) and the 'drive' that causes fuels to eventually saturate with water is simple chemical/physical 'equilibrium' ... the larger amount of fuel mass the greater the 'drive' towards 'equilibrium'.
Once a fuel starts to 'drop out' water, or radically begins to 'condense' on the tank wall surfaces above the liquid ..... its already near to or is fully saturated with water from the atmosphere. If you want less water, simply have less stored fuel.

Tank vent desiccant traps (often changed or often 'regenerated') is the simplest way to keep water out of a boat tank with 'fresh' fuel; after of course, preventing leaks at the 'deck fill'.

BTW 'boat fuel tanks', cannot withstand the 'vacuum' generated if you happen to think that putting a valve on the vent line will stop water vapor uptake ... because you risk IMPLODING such a tank when the temp. goes way down.
NO valves on boat tank vent lines !!!!!!!
01-02-2013 03:31 PM
kellysails
Re: How much water in the fuel filters is Ok?

Great thread!

Quote:
Originally Posted by RichH View Post
How to prevent water in fuel.
1. dont always top-off the tank, especially with a 'large' tank.
Hmmm, I have always understood that you want the tanks full which reduces in-tank condensation. This is interesting.
01-02-2013 02:56 PM
MarkSF
Re: How much water in the fuel filters is Ok?

I do tend to keep the tank pretty fuel, topping it off about once a month. At this point it will normally take about 5 gallons, which leaves about 15 gallons in the tank.

I will try to keep it at a lower average level - say half full? That would be more than adequate for my needs.

I buy all the fuel in a 5 gallon container from the gas station I fill my (diesel) car at.

Good point about the O ring...it's probably as old as the boat!
01-02-2013 02:14 PM
RichH
Re: How much water in the fuel filters is Ok?

Quote:
Originally Posted by MarkSF View Post
I don't have a dedicated separator, just the aftermarket Fram, which is just a filter. Better put a Racor separator on my shopping list, then?

Actually, I'm not sure of the capabilities of the Fram. It does have a drain screw, but the bowl is not transparent. It takes a C1110PL cartridge. Does anyone know if it separates water?
All filters (installed with the filter bowl 'lower' than the filter 'head') will trap water, including the spin on type. . For 'best' water 'knock out' you should have such mounted in the 'very' lowest portion of the entire fuel delivery system ... so that water that 'drops out' from the fuel will drain towards the 'filter'. A cartridge type filter housing (with 'bowl down') with NO filter element installed will trap water.

For non-transparent bowls with drain plugs, either routinely drain them or put a '**** valve' in place of the drain, .... or (against boat and CG regs.) put a small length of fuel compatible clear hose ('translucent teflon-type' is best) between the drain port and terminate the 'tubing' to a **** valve.

If you need to trap air, simply install the filter with the bowl higher than the filter 'head' and put this in the highest portion of the entire fuel delivery line.

FWIW ... if you notice that there is water in a bowl, it means that
1. your fuel is totally 'saturated' with water vapor (usually 'old' fuel, or from a fuel tank that is continually 'topped off');
2. your fuel source is delivering 'old' fuel + water;
3. your deck fill is leaking.
The importance of guarding against free water in the fuel delivery system (besides the fact that water doesnt 'burn' very well) is that water hitting the hot injector tips can shatter them.
4. If you do see 'water' in your filter bowl be aware that the typical filter 'cellulosic' material, even that it is 'resinated' with epoxy compounds, will 'soften' and become weakened ... and you should consider to 'change out' that filter cartridge between 6-12 months and regardless if there is 'dirt' captured on it or not.

How to prevent water in fuel.
1. dont always top-off the tank, especially with a 'large' tank.
2. keep the MINIMUM amount of fuel in the tank to cover your immediate needs, plus some reserve.
3. Drain/empty the tank completely for loooooong layup/storage.
4. Buy your fuel only from a high-turnover source - a fuel source that caters to 'watermen' or a large fishing fleet .... or jug it in from a 'truck stop' --- "Fresh" fuel !!!!!
5. Routinely change the O-ring in your deck fill cap.
01-02-2013 09:55 AM
svHyLyte
Re: How much water in the fuel filters is Ok?

Quote:
Originally Posted by MarkSF View Post
I don't have a dedicated separator, just the aftermarket Fram, which is just a filter. Better put a Racor separator on my shopping list, then?
...
Mark--You would be wise to install a Racor FG500 filter:



One can observe water, if any, in the bottom of the bowl and drain it, if necessary, without difficulty. (If you are finding much water, however, it would be wise to have your fuel tank(s) "polished".) Another advantage of this filter is that the turbine/spindel seen through the bottom bowl "spins" the fuel such that heavier debris is thrown out and collects in the bowl as well where it can be flushed out through the bottom drain.

FWIW...
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