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Wed 20 Oct 2021 16:21

E 10 water in tank accumulation - Lrac

Apologies if this has previously been covered.

I am assuming that petrol is not drawn from the very bottom of the tank into the fuel pump?

We have all been made aware that water will settle at the bottom of the tank so presumably after a period of time it must be unavoidable for our tanks to fill this "void" with water plus we are all told not to let fuel get very low as this can damage the fuel pump so once again causing an area in the bottom of the tank to retain water.

Be interested to hear what other think. Hopefully my assumption is incorrect

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Wed 20 Oct 2021 17:09

E 10 water in tank accumulation - Andrew-T

I guess this will depend on the vehicle, but most cars' tanks are plastic and under the rear seat, with no outlets from the bottom, for obvious reasons. Fuel pumps are connected via a large opening in the top, so I guess the bottom few millimetres of fuel will not be drawn out.

Over time a quantity of water probably collects, perhaps with the fuel, or condensation, or from filling the tank when it's raining. I think a tank can only be completely emptied by removing it.

Ethanol is fully miscible with petrol and with water, but I'm not sure what happens in the three-component mixture. Perhaps any water layer will gradually reach the engine ?

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Wed 20 Oct 2021 21:55

E 10 water in tank accumulation - focussed

It's called phase separation, when the ethanol that is mixed with the petrol, attracts water from the air, until it gets to point when the ethanol in the mix contains so much water that it separates and falls to the bottom of the tank and you end up with an ethanol+water mix and free water as well.

www.bellperformance.com/blog/bid/114018/phase-sepa...0

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Wed 20 Oct 2021 23:09

E 10 water in tank accumulation - Andrew-T

It's called phase separation, when the ethanol that is mixed with the petrol, attracts water from the air, until it gets to point when the ethanol in the mix contains so much water that it separates and falls to the bottom of the tank and you end up with an ethanol+water mix and free water as well.

I would expect a water/ethanol mix to separate from the petrol, but I don't believe you would get an additional layer of water - unless I misinterpret your last line ?

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Wed 20 Oct 2021 23:32

E 10 water in tank accumulation - focussed

It's called phase separation, when the ethanol that is mixed with the petrol, attracts water from the air, until it gets to point when the ethanol in the mix contains so much water that it separates and falls to the bottom of the tank and you end up with an ethanol+water mix and free water as well.

I would expect a water/ethanol mix to separate from the petrol, but I don't believe you would get an additional layer of water - unless I misinterpret your last line ?

Check out the link I posted for clarification.

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Thu 21 Oct 2021 09:54

E 10 water in tank accumulation - Andrew-T

<< Check out the link I posted for clarification. >>

Sorry, still don't buy it. There will certainly be two layers, but I don't believe water will separate from a 'water/ethanol mix', even if it contains some petrol. The two main phases will find an equilibrium. I remain to be convinced - we all know there is some dodgy truth on the web. Unless additives in the petrol have some emulsifying effect ?

Plus the point that this quote is talking about US fuel which may well be different from ours.

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Thu 21 Oct 2021 12:26

E 10 water in tank accumulation - edlithgow

I'd think ethanol containing fuel would tend to remove free water at the bottom of the tank, if fuel consumption was fairly high.

Adding a bit of ethanol or methanol to motorcyle petrol tanks (which tend to rust out at the seams) was a recommended trick. The alcohol acts as a bridging solvent, and the water is absorbed into the bulk fuel.

I drained my fuel tank a couple of years ago via the drain plug, and it did appear to have free water droplets in the last couple of litres, I'd think more probably remained as a thin layer on the bottom of the drained tank.

Last I heard there was no ethanol in Taiwan petrol, there being no significant bioethanol production farming lobby..

Edited by edlithgow on 21/10/2021 at 12:31

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Thu 21 Oct 2021 12:28

E 10 water in tank accumulation - Bromptonaut

Water will separate from petrol and potentially form a layer at the lowest point of the tank. Any car will probably have a small quantity of water from in tank condensation or form potential contamination of uplifted fuel.

Aircraft have fuel drains at the lowest point of the tank to allow water to be drained off. Obviously, the dynamic nature of flight is such that water is going to be remixed with fuel and effect the engine.

In a car the fuel filter may capture small quantities of water. The service instructions for my old XUD engined BX and 205 included draining off water from the filter.

Whether the quantity of water accumulating in the tank is increased by the addition of more Ethanol may be the $20k question.

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Fri 22 Oct 2021 11:16

E 10 water in tank accumulation - edlithgow

<< Check out the link I posted for clarification. >>

Sorry, still don't buy it. There will certainly be two layers, but I don't believe water will separate from a 'water/ethanol mix', even if it contains some petrol. The two main phases will find an equilibrium. I remain to be convinced - we all know there is some dodgy truth on the web. Unless additives in the petrol have some emulsifying effect ?

Plus the point that this quote is talking about US fuel which may well be different from ours.

If water separated from a water/ethanol mix, there would be a layer of 100%water / 0% ethanol in the bottom of your beer glass.

There isn't.

Easy enough to test the behaviour of petrol/alcohol with a whisky bottle with a bit of fuel in it.

Accurately modelling the geometry and venting of your petrol tank might be tricky but probably isn't necessary.

Tipping the bottle on its side and slightly loosening the cap is probably close enough to worst case, though you'd have to give it some kind of roof to prevent direct rainwater ingress,

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Fri 22 Oct 2021 12:12

E 10 water in tank accumulation - Bromptonaut

The theory posited in Focussed's link is that ethanol's hygroscopic properties are sufficient to draw in water from atmospheric vapour to the extent that a water/ethanol mix can drop out. As with, for example adding beer to a fuel tank.

Google doesn't seem to have any convincing answers.

My own though though is that as Whisky barrels are sufficiently non-airtight to allow the "Angel's Share" to evaporate I'm quite surprised that water does not dissolve the proof spirit, at least to the point it does not require dilution after maturing (or that proof/overproof) matured Whisky (eg Glenfarclas 105) is possible.

Even under pandemic/lockdown conditions where a tank lasted months I'm not worrying too much about my petrol Fabia...

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Fri 22 Oct 2021 14:29

E 10 water in tank accumulation - Andrew-T

The theory posited in Focussed's link is that ethanol's hygroscopic properties are sufficient to draw in water from atmospheric vapour to the extent that a water/ethanol mix can drop out. As with, for example adding beer to a fuel tank.

Beer is 95-97 % water ! Water (or beer) added to 'neat' petrol will settle straight to the bottom - it is 99.99% immiscible with hydrocarbons. Petrol containing 5 or 10% ethanol (miscible in all proportions) is different, as water tries to mix with the ethanol but not the fuel. The result is two layers, fuel with some ethanol on top, water with (most of) the ethanol below.

A tank of neat petrol (as it always used to be) gradually accumulates moisture from various sources (as described above). With E5 or E10, any free water will mix better and will probably be gradually fed to the engine. Over time your fuel tank may be purged of damp ?

On the other hand E5 or E10 will probably be a bit damp to start with, because of the ethanol content.

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Sat 23 Oct 2021 03:45

E 10 water in tank accumulation - edlithgow

I also drained the tank via the drain piug on my UK Nissan Sunny, after accidentally putting diesel in it. No sign of water, so maybe the ethanol in UK petrol took it out.

EDIT Looked it up. No ethanol prior to 2008, so my theory isn't supported by this anecdotal evidence.

Lots of variables, of course, including the consistently high humidity in Taiwan

Edited by edlithgow on 23/10/2021 at 03:49

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