Removing Diesel in Fresh Water Tanks

From time to time I do some incredibly stupid things.  I suspect everyone is prone to do the same – but they just keep quiet about it.  My latest dumb act is perhaps worth sharing, who knows it may help some other unfortunate idiot in the future.

Somehow, I managed to stick the diesel filling nozzle into the fresh water tank filling pipe.  Why?  I have no idea.  I have fuelled Truce many times and never even come close to opening the water cap instead of the diesel cap.  The caps are of course different sizes and the water filler is clearly labelled ‘WATER’.  I can only blame it on the distraction of having Ngozi on board – but that’s a weak excuse.

Jabsco Drill Pump - photo Ray Penson
Jabsco Drill Pump – photo Ray Penson

Anyway, I had stuck the diesel nozzle in the water fill pipe and merrily latched the trigger open to start the diesel flowing.  After a few seconds the nozzle clicked off indicating the tank was full.  Very strange I thought as the diesel tank was almost empty.  Then I realised my mistake – the awful realisation that I had messed up on a huge scale – unbelievable.  One of those John Cleese moments, I sat down, looked around, looked again at the open fill pipe in disbelief.  A jumble of thoughts rushed through my mind, how, why, etc.  I had put a good slug of diesel into the almost full port side fresh water tank.

It was at this time that Ngozi helpfully asked why I had not painted the caps of the fillers different colours, (as we do on commercial ships).  My thoughts turned dark and murderous.

Now I had to set about the clean-up.  Having been at sea many years I had experienced diesel in fresh water tanks previously.  Not a common occurrence, on most ships almost impossible to achieve as the systems are separate – but not beyond the resourcefulness of some talented engineers.  Diesel is very persistent and its hard to get rid of the smell and taint even after many cleanings and flushing’s.

I knew there was no urgency, the damage had been done so it was off home to think about it overnight.  Here is what I did to clean up the mess.

The first thing is not to circulate the fresh water in the tanks and keep as much of the system isolated as possible.  Don’t run water pumps and keep the boat as still as possible to avoid mixing the diesel floating on the water with the fresh water beneath.

I removed the outlet hose from the bottom of the fresh water tank, opened the valve and ran the water from the tank directly into the bilge.  There is no problem here as the diesel floats on top of the water.  When the water had dropped in the tank to a level below the inspection cover I closed the outlet valve.  Upon removing the access cover to assess the situation in the tank I found a good layer of diesel on the water.  I then rigged up a drill pump with two short lengths of garden hose and started sucking the diesel from the top of the water into a jerry can.  Many jerry cans and trips to the waste oil tank in the marina followed.  I had removed most of the diesel and a good deal of water.  I then dropped the remaining contents of the tank into the bilge.

I was surprised how much diesel was now floating around the bilge and set about removing that from the water interface with the drill pump – a few more jerry can trips followed.  The manual bilge pump removed the clean water from the bilge.

I cleaned the fresh water tank with warm water and washing up detergent.  The water I had to boil on the stove.  I filled up the tank with fresh water and drained it out to the bilge.  Then repeated the whole process again.  The tank and water still had a diesel smell, so I went home to have a beer and think some more.

An internet search turned up a product called Bio Magic that claimed to address my problem.  It sounded too good to be true but a quick call to the helpful people at Bio Magic resulted in them delivering a plastic can of the weak looking liquid to my home the next day.  Would Bio Magic remove the diesel smell, seemed like snake oil but with few options left I was willing to give it a try.  I followed the Bio Magic instructions, added Methylated spirits and left it in the tank overnight to do its job.  Bingo, the next day I drained and flushed out the tank then refilled it.  The diesel smell has disappeared. The fresh water tanks are back to normal again.  Bio Magic works, I have no idea how or what’s in it, but it did the trick.

Now there is more to this tale.  As we know everything happens for a reason.  As the boat was in turmoil and floor boards were up I could see the bilge needed cleaning and that some limber holes were blocked with accumulated crud.  I had the hose pipe in the boat and cleaned all the bilges up spotlessly, removing any diesel residue with bilge cleaner.  I also opened up the other two fresh water tanks and cleaned them then flushed multiple times with fresh water.  In the last fresh water top up I added a cup of bleach to each tank.

All is sweetness in the bilge and the fresh water tanks are clean.  Happiness and harmony on board again.  At some stage in the future I will paint the filler caps, black for diesel and green for fresh water.

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