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According to my research most cars do not seem to have a drain in the gas tank.

This is obviously a problem because there is no way to get water and sediment out of the bottom of the tank if there is no drain. It became a problem for me the other day because there was a warm, humid day followed by a cold night which produced condensation in the tank, then I parked on a slope, which apparently pooled the water. Then the car would not start because it was sucking water.

Airplanes always have drains in their tanks so that all water can be removed. Why are there no drains in car gas tanks? Can I make a drain in my gas tank?

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  • You should take this up with the car manufacturers. If you don't want to go that route, there is the tried and true method of drilling a hole in the bottom of the tank, letting the water drain, then putting a tap screw back in hole to plug it up. – Pᴀᴜʟsᴛᴇʀ2♦ May 22 '18 at 12:40
  • " Can I make a drain in my gas tank?" We don't know what your mechanical skills are. Sure it can be done if you have the knowledge and skills. – Moab May 22 '18 at 14:54
  • @Moab Well, it does not seem obvious to me. For example, most through hull fittings have nuts on both sides, so that would require being able to get a wrench inside the tank which might not be feasible. – Cooter Davenport May 22 '18 at 15:59
  • Welding is an option - if your welding is good enough and your safety preparation is exemplary... – Solar Mike May 22 '18 at 16:14
  • @SolarMike Welding on a gas tank, kaboom! Like I said we have no way to determine their skills and knowledge. – Moab May 22 '18 at 19:14
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Well, some vehicles do, but it adds complexity, weight and cost.

As for why they are not fitted as standard, then that becomes more involved. You say that one humid day and one night was sufficient to cause enough water - I would suggest that the water had been collecting over a period of time and when you parked on the slope was sufficient to then be drawn into the pump etc.

One way of avoiding this is to keep the tank between half and full reducing the volume of atmosphere in the tank over time.

As for the comparison with airplanes - a car has a fuel tank of about 70 to 120 litres, the A380 has a full fuel load of 320000 litres which if you start to think about a 0.01% water contamination is something to be considered, especially at 32000 feet... Fuel contamination in a car on the side of the road is not the same thing...

Some cars have a fuel filter combined with a sediment / water trap which can easily be drained. This can be an easy retro-fit if one is having water contamination problems - and these can be due to some filling stations of dubious quality...

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  • I was talking about small aircraft like Cessna 172s, not large commercial aircraft. – Cooter Davenport May 22 '18 at 13:19
  • No Cessna mentioned in your original question, but 53 gallons is over 200 litres... It's the risk level that is considerable compared to a car... – Solar Mike May 22 '18 at 13:22
  • That is pretty interesting about the sediment trap filter. I did not know those existed. – Cooter Davenport May 22 '18 at 15:42
  • One is made by Lucas CAV for diesels... – Solar Mike May 22 '18 at 16:12
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My 1971 Datsun 240Z definitely has one. I think all the Z's from 1970 - 1978 had drains. Can't confirm with absolute certainty. So, some older cars have drains.

If you can drop the tank without removing it completely you can usually get access to the inside of the tank through the fuel level sender opening.

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I have never seen a drain in an auto tank. When I had a problem , I pulled out the tank and cleaned it . It was not difficult, an older, full size Olds. I also drilled a hole , drained a tank and put in a self tapping screw but this is not a long term condition.

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  • The drain plug was very handy at times on my old landrover... – Solar Mike May 22 '18 at 16:59
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Probably the same reason so many cars have a hose-block in the fill tube; To make it harder for people to steal gas.

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