Who left the diesel tank cap off?

howardclark

howardclark

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Don’t think it matters- it’s still my responsibility.
The question is how much do I need to worry? It is two weeks since we topped the tanks up and there has been a fair bit of rain since. Both tanks are 50 gallons & not connected. so I have the option for now of just running on the other tank.
There are Racor water separating filters on each tank and after an hour of running no sign of any water in the filter bowl.
So will water not get sucked up until we sail and roll about or will it only happen if the level is low allowing for more ‘sloshing‘?
 
If your filler neck is exposed to the sky then some rainwater must have entered but it sounds as if your tank dip pipe / bottom exit has a "dead space" and the water level is below the exit. However, when the fuel is sloshing around, it is likely that some will find its way out.

Do you have a tank drain as that should be in a sump and have no dead space so you can just run off the water. If not, you could either remove the sender/filler plate from the top of the tank and push a tube down a siphon out the bottom or keep an eye on the water separators and be prepared to drain off the water as it appears in the bowl.

You can buy stuff that will help to put the water into solution but I'm not sure whether that is advisable if you're talking about quite a lot of water.

Richard
 
Most of the water is likely to be at the bottom of the tank and may have a sump, even if it is just a tiny depression. Some water may still be in beads elsewhere and will move down after movement or subsequent filling. I'd suggest opening the tank, inserting a pipe to the bottom and pumping out any water. There's a good chance that you won't have an access port but should be able to remove the fuel level sender for access. The fuel sender is often sited close to the deepest part of the tank (for obvious reasons). Removing the sender may be a problem if your tank is brim full and you would need to pump some out to lower the level.

I wouldn't expect you to pick up water in the fuel feed when the boat is static. The pipe is usually raised well above the tank base. You usually get problems in bad weather when there's a lot of movement. Unless you managed to quarter fill the tank with enough water to reach the take off pipe.. :D

Forget trying to dissolve the water if there's a lot and it is a much better idea to find out how much is actually there first.

My Jeanneau has a small sump in the tank but the access point is on the side and only a few mm above the hull. I designed the tank on my previous boat and it had a decent sized sump with a blanked off outlet at the bottom. It was really easy to check for water, even with a full tank.
 
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+1 water IS in the tank, and once sloshed around will be picked up. I once nearly ended up on a lee shore in F6 after a bumpy passage because muck I didnt know was there was stirred up and blocked the filter. You need to get it out before you use the boat again
 
Unfortunately have no sump or bottom drain! Back of a fag packet calculation says if we had 2 inches of rain in the past two weeks, about half a litre of water would get in directly which isn’t too scary in a 250 litre tank - will switch to the other tank for now but maybe run from time to time on the other tank and see if water appears at the separator- v easy to drain from there
 
If the rain water runs down the side deck then over the filler you could have quite a bit of water in there. My thought would be to pump out the majority then run the engine right down on that tank, then pump out what's left for disposal. At least that's what I did.
 
howardclark said:
... maybe run from time to time on the other tank and see if water appears at the separator- v easy to drain from there
Click to expand...

I think that is bad idea because the water may cause diesel bug to start growing. If the boat has not moved it should be relatively straight forward to stick a pipe in and draw off the bottom of the tank. You could, for example, deliberately heal the boat, say bow down, then aim the pipe at that low point and draw out the water.

I use a Pella style oil extracting vacuum pump to drain off water from the bottom of my tank from time to time. The Pella has stiff but flexible plastic pipes, small diameter copper tubing could also be used to bend towards the low spot.

Good luck with whatever you do.
 
Does the tank have an inspection hatch in the top?
If so finish this season on the other tank, run that one low, this winter pump through a coalescing filer from the rainy tank. Mop and clean out.

If there is not an inspection hatch, put one in.
 
Well just realised I am 100% guilty- it wasn’t left off when we topped up but when I was fashioning a dipstick last Thursday ( fuel sender is playing up) . Interestingly on recommendation from someone on this forum had purchased some Kolor Kut which I was able to apply to the new dipstick. Shows water just in the lowest 12mm of the tank, so probably as expected. Will pump out from the bottom ASAP but in the meantime quite happy to use the tank in calm conditions
 
Only access is from the filler unless I dismantle a significant part of the pilot cabin. Have got a 240 volt diesel pump plus rigid copper for pumping out- had to do it several years ago- messy job
 
Put the cap on & pour a bucket of water over the deck to see if any actually goes over the filler. That will indicate if water running down the deck is likely to have gone into the tank. If not then things may not be so bad. A 50mm diam hole in light rain lets in a fairly limited amount of water. A pella pipe into the tank whilst at rest would be a good idea if it is possible to drain the bottom contents as suggested above. Then go out with plenty of spare filters & sea sick pills. (y)
 
howardclark said:
Unfortunately have no sump or bottom drain! Back of a fag packet calculation says if we had 2 inches of rain in the past two weeks, about half a litre of water would get in directly which isn’t too scary in a 250 litre tank - will switch to the other tank for now but maybe run from time to time on the other tank and see if water appears at the separator- v easy to drain from there
Click to expand...
Given the amount of water that has been falling from the sky in the South West of England over the last 48 hours/week are you sure about that?
 
howardclark said:
Well just realised I am 100% guilty- it wasn’t left off when we topped up but when I was fashioning a dipstick last Thursday ( fuel sender is playing up) . Interestingly on recommendation from someone on this forum had purchased some Kolor Kut which I was able to apply to the new dipstick. Shows water just in the lowest 12mm of the tank, so probably as expected. Will pump out from the bottom ASAP but in the meantime quite happy to use the tank in calm conditions
Click to expand...

Thats a lot of water. How many times would that fill separator and stop the engine?
 
If you don't try and remove it quickly you will get bug growth which will make things a whole lot worse-leaving the lid off also allowed airborne microbes to enter.
 
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howardclark said:
Well just realised I am 100% guilty- it wasn’t left off when we topped up but when I was fashioning a dipstick last Thursday ( fuel sender is playing up) . Interestingly on recommendation from someone on this forum had purchased some Kolor Kut which I was able to apply to the new dipstick. Shows water just in the lowest 12mm of the tank, so probably as expected. Will pump out from the bottom ASAP but in the meantime quite happy to use the tank in calm conditions
Click to expand...
I would probably shock dose that tank immediately with Marine16 or similar to reduce on-going build up of bug. It does sound as if there's a lot of water unless your tank is very tall and narrow. A more normal layout would probably mean at least 5 - 10 litres in the bottom of a 250 litre tank. A large surface area at the oil/water boundary and warm weather will encourage rapid growth. I would certainly not be tempted to leave it until winter before removing the water. Doing it ASAP is a good decision.
 
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Mistroma said:
Most of the water is likely to be at the bottom of the tank and may have a sump, even if it is just a tiny depression. Some water may still be in beads elsewhere and will move down after movement or subsequent filling. I'd suggest opening the tank, inserting a pipe to the bottom and pumping out any water. There's a good chance that you won't have an access port but should be able to remove the fuel level sender for access. The fuel sender is often sited close to the deepest part of the tank (for obvious reasons). Removing the sender may be a problem if your tank is brim full and you would need to pump some out to lower the level.

I wouldn't expect you to pick up water in the fuel feed when the boat is static. The pipe is usually raised well above the tank base. You usually get problems in bad weather when there's a lot of movement. Unless you managed to quarter fill the tank with enough water to reach the take off pipe.. :D

Forget trying to dissolve the water if there's a lot and it is a much better idea to find out how much is actually there first.

My Jeanneau has a small sump in the tank but the access point is on the side and only a few mm above the hull. I designed the tank on my previous boat and it had a decent sized sump with a blanked off outlet at the bottom. It was really easy to check for water, even with a full tank.
Click to expand...
;)

Richard
 
[
howardclark said:
Unfortunately have no sump or bottom drain! Back of a fag packet calculation says if we had 2 inches of rain in the past two weeks, about half a litre of water would get in directly which isn’t too scary in a 250 litre tank - will switch to the other tank for now but maybe run from time to time on the other tank and see if water appears at the separator- v easy to drain from there
Click to expand...
howardclark said:
Well just realised I am 100% guilty- it wasn’t left off when we topped up but when I was fashioning a dipstick last Thursday ( fuel sender is playing up) . Interestingly on recommendation from someone on this forum had purchased some Kolor Kut which I was able to apply to the new dipstick. Shows water just in the lowest 12mm of the tank, so probably as expected. Will pump out from the bottom ASAP but in the meantime quite happy to use the tank in calm conditions
Click to expand...

I think 2 inches of rain would introduce much less that half a litre unless you have an exceptionally large filler.

12mm of water suggests there was already quite a bit ( most of it) in the tank
 
I have a sump but in this case I would remove the water with a Pela from the bottom of the tank then treat the fuel with anti bug and just use it from there.
 
I would heel the boat and get as much water out from the bottom of the tank as possible.
A Pela oil extractor is quite good for this.
I would be careful about adding anything to the diesel until the water has been removed.
Get plenty of cans (HDPE milk bottles will do if you are careful) and keep taking fuel out until you stop finding any dirt or water.
If you remove a mixture of water and diesel from the bottom of the tank, it can be left to settle out.
If the diesel ends up clear, not cloudy, it can go back in the tank.
I would sample the bottom of the tank every couple of weeks to be sure you're not getting any bug growth.

There is usually some water in fuel, the name of the game IMHO is to be sure there's never going to be enough water or dirt to overcome your filters.

Having got that fuel wet, I would want to use it up in preference to fuel that had not been abused.
If it's not going to get used in a couple of months, then a biocide is probably in order, but bear in mind most of those products only give a finite shelf life for the treated fuel if you read the small print.

Make sure you have spare filters on board of course!
 
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