Testing fuel time with plain water ❓❓❓

[Andrew Anunson]

Don't use water to test your fuel system unless you can get all of the water removed fairly quickly. Water supports life.... stuff will grow in your fuel lines, filters, valves, and any inaccessible areas of the tanks that don't get dried. Also, as water evaporates it leaves a residue of minerals that will later show up in your filters / fuel system.

[dlloyd3]

Why are you guys even discussing this? Water will not leak as easily as air. Follow Van's directions and test with air, a little pressure and some soapy water. I have seen tanks that leaked. If they leak, the leaks are not difficult to find. You won't find any more leaks using gasoline of any octane but you may discover fire.

[majuro15]

I did a test at your point with water and glad I did. I had a weeping rivet and a monsterous hole that I forgot to seal somehow. I didn't treat the water test as the only or final test, just an initial pass.

Fill them up with water, fix your leaks, then move on. Once the back baffles are on, do the regulated air check with soapy water and a balloon for a final leak check.

Note, this is not testing the fuel SYSTEM, just the tanks themselves before the rear baffles are installed. If you can finish the rest of the build before that water dries up, I aplaud you!

[sglynn]

Test with fuel. Water contaminates the tank. If you price by the bottle, fuel is cheaper. When you are finished put the fuel in your car its not wasted. Still do air test, per Van's instructions.

[ChiefPilot]

Be aware that just because no leaks were found using water doesn't mean that leaks won't be found when the tanks are filled with gasoline. This is where testing with air (via a toy balloon or similar) is more effective.

Case in point is the Mr. Funnel line of gasoline filters - gasoline flows right through but water does not. Now imagine a leak the size of a hole in the Mr. Funnel filter. Water won't escape, but gasoline (and air) will...

[Mel]

Originally Posted by sglynn

Test with fuel. Water contaminates the tank. If you price by the bottle, fuel is cheaper. When you are finished put the fuel in your car its not wasted. Still do air test, per Van's instructions.

Not a good idea to put aviation fuel in a car. If your car has a catalytic converter, as do most, the lead will contaminate it. You will discover this on your next emission inspection.

[BMC_Dave]

As previously discussed, test with a liquid that won't foster the transfer of ions and is one of the strongest universal solvents... Use air (best), or gasoline (at least useful).

[sglynn]

Originally Posted by BMC_Dave

As previously discussed, test with a liquid that won't foster the transfer of ions and is one of the strongest universal solvents... Use air (best), or gasoline (at least useful).

I've put "used" AVGAS in my cars many many times. Small amounts relative to tank. No issues what-so-ever. Also works well in my tug and lawn mower.

Point is test with fuel.

[Bavafa]

Folks, some of you are not reading the post and the question and providing suggestions. The tank is still open on the back side and the intention is to catch any possible leaks before closing it completely.

[BillL]

Closed or open, I would not use water. Water is almost a universal solvent, it dissolves stuff, when it does, there are ions, with ions there is corrosion. If you try to dry it, the solids will remain and corrode with the next drop of water in contact. I would not want corrosion.

If you must test before closing, automotive gasoline would be a suitable substitute, but you should be sure the pro seal is fully cured. Mineral spirits (Varsol, stoddard solvent) might be a suitable substitute and much less flammable.