USS Nimitz Jet Fuel in Potable Water Tank

Does anyone who served on a carrier have any idea how jet fuel could end up in a potable water tank?

I can’t imagine any logical reason (even by Navy standards) why there would be any cross connection between JP5 tanks and potable tanks. So short of a crack in a shared tank wall (which should trigger a much more serous response), a massive screw up with a contaminated potable bunker hose, or a crazy crossover, I’m at a loss how this could happen.


According to a USNI News report, it is possible for drinking water can become contaminated with jet propellant-5 because the two mix in a ballast tank system used by the Nimitz. A ship’s ballast tank system helps control its buoyancy and stability.

That makes no sense.

Why would a potable water system be tied to the ballast? Why would cargo tanks be tied to the ballast?

“ The fresh water in the ballast tanks — which naturally separates from the fuel — can be used for potable water.”




Some classes of navy ships use ballast compensated fuel tanks that puts seawater in to fuel tanks connected in series such that the draft of the vessel doesn’t change as they consume fuel. However I didn’t think Carriers used that system, but maybe they do. But my understanding of compensated tanks is that its seawater…even if they used fresh in JP5 tanks I can’t fathom that the author is correct in that would be subsequently be used for potable.

In another USNI article it says:

A Navy official told USNI News on Wednesday that the JP5 entered the potable water system due to a procedural “line up” issue, rather than a fuel leak or a tank failure, that accidentally pumped the fuel into the fresh water system.

If somehow that discharged saltwater was contaminated & then siphoned or mixed with the raw water system that feeds the distiller/evaporator freshwater makers then the potable water would become slightly contaminated. Or a crack between a fuel/JP5 tank & the salt water supply to a freshwater maker, that will cause a very slight contamination of the potable water system too. Been there, done that.

Something like that had occurred to me…I was on a ship that had the MSD overboard slightly forward of the water maker feed water intake…that particular design flaw always bothered me.

It sounds like from the other article that the Navy is saying it was pumped in though, and if the sailor’s water sample photos from one of the other articles are to be believed then it was a bit more than “very slight” contamination.

As for their response, it sounds like they are just flushing the tank, fill/empty/fill/empty. You’d think there would be a requirement to empty and actually physically clean and then super-chlorinate the tank after. I thought the navy had guidelines for everything, especially drinking water safety on a warship!

Me too. On a couple of vessels I worked, I would only operate the water makers while underway because the MSD discharged forward near the water line & the water maker feed came from under the ship. If stationary offshore then one or the other would be secured.

Concerning the “very slight” adjective. If it wasn’t very slight then they should call some lawyers for medical concerns & the USCG, state of California, harbor police, etc. for environmental concerns. Luckily my experience was “very slight”.

I’m not so sure about navy systems. I’d just have to assume that for extreme tactical reasons the ability to move fuel water anywhere aboard would be a necessity but when it comes to pot water i’d think they’d be forced to use the deck pump and fire hose?
i’m not even sure a pot tank can share a wall with a fuel tank, it can’t in our world but the navy? I’m inclined to agree with shipeng (?) above who mentions raw water feed to the evap. and NO, I am not buying the fresh water used as ballast, in a emergency that bad they’d use a fire hose and deck pump if need be before sending pot water into a ballast tank. I can’t see that. many of my ships had a fire hose connection to the pot tank, (for supply… and sometimes cleaning the deck !!!

Doesn’t the Navy use bladders to keep fuel and water separate on the mixed tanks or am I mis-remembering?

No, there are no bladders separating the fuel and water, just the relative density. There is a decent explanation of an example of the tank systems here. That’s why during an unrep if the navy boys aren’t watching their gauges properly you’ll see ballast overboard change from seawater to unmistakably not seawater.

But as mentioned, I don’t think carriers use compensated fuel tanks. And with some more digging I found a study on correcting the Nimitz’s inherent starboard list that mentions she has the ability to use potable water as fresh water ballast in some tanks, voids, DC voids…and possibly some voids that may be used for JP5.

The problems encountered with using SW in tanks may be common knowledge to most people; however, potential corrosion from using salt water has encouraged some carriers to use potable water (PW) as a means to fill their list control tanks. The LCS [List Control System] is designed with PW as a back-up to using SW or firemain. This is advantageous for corrosion issues, but can be a problem for PW inventory. Any leaks in the system or maintenance requiring system fill and drain could use a large amount of PW. When underway, potable water conservation is of primary importance.

And as anyone who’s worked with plumbing knows, where there are cross connections, there is potential for contamination…

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I reached out to a buddy who was on a Nimitz class and he said this was pretty common. According to him, carriers often operate in a rectangle pattern during flight ops thus going over the same water over and over. The aircraft commonly dump excess fuel prior to landing and this gets sucked into the SW intakes including for the evaporator.

I asked about the fact that fuel floats and the intakes are presumably 30 feet or more below the waterline and we’re assuming that a ship of that size doing 25+ knots stirs up the water enough to cause this phenomenon.

In my opinion, the Navy’s public statement that the cause was sailor error in the form of an improper valve lineup needs to be vetted. While I can certainly understand their reticence to not highlight the intentional dumping of fuel (especially for California based carriers), pardon me if I’m skeptical of pointing at the nearest E4 and saying ‘that dumb blue shirt is the culprit.’


Was on an old destroyer back in the early 70s’, there was a sheen in our potable water, had an oder as well, fuel in potable water was common back then, guess things don’t change

If you sprinkle ground black pepper on it the pepper will absorb the oil and you can drink through it.
Well, it works with vodka.


In 1978, I stepped into a shower aboard USS Saipan (LHA-2) and the fluid coming out of the shower head was diluted with JP-5. I cleaned myself off, walked to a telephone in the berthing compartment and called the Oil King, in charge of all inter-ship fuel cargo, and told him what was happening, along with my distress in not being able to take a shower. I went to an adjacent berthing compartment, with good potable water coming from the shower head and that was that. Many naval vessels have complex, inter-connected fluid systems that can transfer potable water, seawater ballast, diesel fuel and aviation fuel. Normally these systems are segregated but once in a while human factors come into play and during fluid transfers a variety of one type of fluid goes to the wrong location. That’s just the way it is and always will be, cause sailors are human. Never saw sailors exposed to diesel fuel or JP-5 suffer from long-term effects.

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I know you are correct, but you shouldn’t be. This is the type of situation where even a layman would start with “I’m no engineer but…”

But I AM an engineer and this is preventable. You can absolutely engineer this out. There is never any reason you would transfer JP5 into a potable tank, and therefore the system should/could be designed to prevent this, even if it means segregation at the piping level.

But there is obviously a cost in physical space, dollars, and complexity. And clearly the vessel designers have not allocated as high a value to crew safety as they have to contingency/damage control/options. And perhaps that’s a valid calculated decision.

I once managed a project retrofitting a fluid system for idiot-proof fluid segregation, since a screw-up would cost the vessel lessee (charterer) millions of dollars. So it can be done. But I suppose in the government’s eyes this particular screw-up scenario cost it nothing of value, and that is sad.


I cannot conceive of any plumbing system mixing fuel and drinking water. That is several levels beyond crazy. I am not so sure that drinking kerosene in small amounts is harmless, but even if it is there are additives that are commonly put into jet fuel that are quite toxic.
As for watermakers, I have no experience at all with distillers, but I did a lot of work on RO watermakers and the tinniest bit of petroleum ruins the membranes. If our customers had any intentions of using them in anything put clean ocean water we sold special prefilters that removed hydrocarbons. We also had a UV sterilizer we could add on the output side to kill any germs that fit through the membranes.

If there was only some way to properly segregate different pipelines. Like spectacle blinds. Or spool pieces.

You know, like every tanker has.

Dirty hose and/or leaking bulkhead.