Oil in aluminum water tank

[KrazySailing]

The boat has two water tanks one aluminum and the other polyethylene.

Had diesel fuel in the aluminum water tank of a 45 year old aluminum hull sailboat The tank is built in; the bottom is epoxied and attached to the hull. The sides and top are not attached to the hull . The tanks appear to have been lined with something (epoxy??)

Took about 2 gallons of oil off by dipping and the remainder by pouring the water oil mixture into a 5 gallon water carboy, filled it to the top and decanting the oil from the narrow opening.

Then several cycles of pressure washing and scrubbing with stainless steel brushes. Still a little oily smell and debris.

We'll next try a degreaser.

Suggestions on cleaning the tank? We'll likely use the polyethylene tank for drinking water and put filters on the aluminum tank.

There are seven 8 inch inspection ports with rubber/neoprene gaskets that now have an oily smell. Any idea on how to get the oil from the gaskets?

[a64pilot]

If it feasible I think steam cleaning will emulsify the oil and it will be removed that way, but I'd try simple green first.
Replace the gaskets, I think the fuel is inside of the rubber and you'll never get it out.
Maybe plastic tank to galley sink for drinking only and metal tank for washing etc, no consumption?

[model 10]

I think you may need to use alkali or caustic soda cleaner and ditch all the gaskets. The coating on the inside is a little scary. It may have soaked up fuel and you will never get rid of the taste unless the cleaner can clean down far enough into the coating. You can get dense (and $$$,) carbon filter elements that might remove some of it.