Water in Petrol Tank(s)

[aesmith]

What's the best way to get rid of water once it's got into a petrol tank?

This was from the fuel tank from our inflatable, which doesn't get much use, doesn't even get topped up some years. I couldn't say when it was last actually emptied.

Anyway I tipped a couple of litres from the outboard tank into the chipper, with no problems. The rest went into the ride on mower, which is where the water showed up when it died after a couple of minutes. After finding water in the carb, running off samples from the tank until it appeared clear, I ended up having to drain the tank right empty, tipping the mower up to make sure. A bit of fresh petrol and it fired up and seemed to run perfectly well although I only tested for a few minutes.

Next day it died within a few seconds of starting. Water in the carb again. Not just that but a sample drawn from the tank had more water than petrol. I've drained the tank again, and with fresh petrol (again) it seemed OK at least for a brief test.

So the question is still, what's the best way to make sure all water is truly gone, and not sitting in drops or a film or something waiting to suddenly drop to the bottom? As well as the mower I need to deal with the outboard tank, which I can leave open for a few months to dry on its own. And the chipper is suspect as well, since it had some of the dodgy fuel.

 

[Bullet2012]

https://www.amazon.co.uk/Bardahl-Additive-Contained-Promotes-Water-Diesel/dp/B07JGFKQTB

 

[jmp49]

You can kolorkut a fuel tank's fuel to see if its still water contaminated.
Someone will find you a better link, but this stuff :

Pardon our interruption...

 

[minimutly]

Tilt the tank so the water is at the bottom, siphon it out from there.

 

[Seadog]

The old method was to pour meths into the tank. Meths mixes with water and, provided that it's not too diluted, it will still burn.

 

[8ob]

Nothing worse than having fuelling issues on a boat, my money would go on an inline water separator.

Bob

 

[dave h 2]

Have a look at U tube films that remove the alcohol from modern petrol. They use water to absorb it.
I have removed blobs of water from a float chamber with a paper drinking straw (some plastics melt) or rubber tube. Finger over the top of the tube, put straw in the water, remove finger, tube fills with water replace finger and lift tube out of petrol

 

[colnerov]

A partially filled tank will create condensation, so when laying up the tank either drain it or keep it full. Your choice.

 

[aesmith]

Tilt the tank so the water is at the bottom, siphon it out from there.

That was exactly what I did except I emptied everything. Then after adding fresh petrol it picked up water again. I guess the water was in drops sticking to the tank sides by surface tension.

 

[aesmith]

Nothing worse than having fuelling issues on a boat, my money would go on an inline water separator.
Bob

I might look at that for the inflatable if I can work out how to mount it. The transom folds down (forwards) when the boat's packed up so couldn't have anything permanently fitted there.

But it's a concern that I was using the boat with that water building up and possibly might have got to the engine at an inconvenient moment.

 

[brightspark]

use e5 petrol e10 has water in it i wont use the stuff on my norton bike generator and garden gear

 

[Barking Mat]

Nothing worse than having fuelling issues on a boat, my money would go on an inline water separator.

Bob

View attachment 491020

What @8ob said.

 

[aesmith]

What @8ob said.

Although I agree with you both in principle, our inflatable is only used on inland water or close inshore. Places where it is always possible to reach safety by rowing.

At the moment I first want to get the three petrol tanks decontaminated. The mower might already be there, but I'm thinking maybe to use some of that water removing additive for the first couple of fills.

Longer term for the inflatable I might just make sure the tank gets fully emptied at the end of each season, and try to remember to close the vent every time it's left. We've used it for something like 10 years and this is the first time I've become aware of a problem.

 

[aesmith]

I just got around to looking at the nearly 5 litres of suspect petrol, decanting some into glass bottles. First bottle full looks like, smells like and probably is just petrol. No suspicious bits collecting at the bottom. Second bottle looks like a good 50% water. Third bottle pretty much the same as the first. Quite an eye opener first that there could have been that much water kicking around in the first place. Secondly the random way it came out, first none, then a great dollop (350ml) then nothing.

 

[Smallfry]

Condensation is always a problem with seldom used machinery and vehicles, and you would be surprised how much collects in the bottom of tanks. Used to be a problem with domestic heating oil tanks too. There are water dispersants available that you can add to the fuel, but its not ideal IMO. Some sort of inline filter will be better.

This is one of the reasons why the motor industry has gone over to HDPE tanks, does not suffer anything like as much as metal tanks.

Is your tank metal ? I would suggest changing it for a HDPE "Hulk" tank or similar, with quick release couplings and hose, so it can be removed and taken indoors when not in use.

Another thing is the cap, if the sealing is dodgy and it is left out in the rain. Something you can do nothing out though is venting. As the fuel is taken from the tank, it is replaced by air, otherwise it will cause a vacuum and stop the engine. How is your tank vented ? Is it via closable valve on the cap, which you MUST remember to close after use, or it could let water in, or by a pipe, which could drop to the floor and suck in water.

 

[Guzrik]

Would it be a problem to add a little spiritus every now and then?