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Testing fuel time with plain water ❓❓❓

romanov

Well Known Member
Fellow builders,

I have sealed the tanks and still
dont have real fuel liquid close by.

Can I test the tanks with just watter?
How accurate is that testing?
Is it possible that watter won't leak
and 100LL later will.

Egibyb9.jpg


Thanks a lot
Roman
 
Why not test it with air? Put a couple of PSI in the tank and spray the outside with soapy water, any leaks will cause bubbles to form.
 
100LL

Sure, no bad in the initial try. But should I go
on and insist on real 100LL test?

Yes, Water has a much higher surface tension than 100LL. While it might not leak with water it doesn't mean that it is still 100% leak proof. You would be much safer to do the final test with either properly regulated air or 100LL.

The initial test with Water should be fine to test for larger leaks. If there are any of descent size then water will still leak.
 
Yes, Water has a much higher surface tension than 100LL. While it might not leak with water it doesn't mean that it is still 100% leak proof. You would be much safer to do the final test with either properly regulated air or 100LL.

The initial test with Water should be fine to test for larger leaks. If there are any of descent size then water will still leak.

+1

Without pressure, solvents, such as gasoline, can easily weep through spaces that water cannot, due to the lower surface tension.

Larry
 
Yes, Water has a much higher surface tension than 100LL. While it might not leak with water it doesn't mean that it is still 100% leak proof. You would be much safer to do the final test with either properly regulated air or 100LL.

The initial test with Water should be fine to test for larger leaks. If there are any of descent size then water will still leak.


Ok second question: is 95 octan as good as 100LL
for real tank testing ❓
 
mogas

Ok second question: is 95 octan as good as 100LL
for real tank testing ❓

I have never flown with MoGas. I am not sure what the surface tension is. If you are flying with MoGas checking with that should not be an issue. If you are I would use non Ethanol for testing purposes.
 
The gas is the same. 100LL just adds lead and some other additives to it and leaves out some additives found in auto gas. Surface tension of all gasoline is pretty much the same, as is it's viscosity.
 
water

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.
 
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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.
 
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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!
 
test with fuel

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.
 
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...
 
Don't put AvGas in car......Lawn mowers, yes. Car, no.

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.
 
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).
 
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.
 
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.
 
With tanks . .

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.
 
I tested my tanks with water before closing the baffle. I was glad I did that because I discovered a couple of leaks and it was easy to fix them with the tanks still opened.
 
Guess I'm planning on bucking some of the advice given in this thread.
Currently I think I'm in about the same place as Roman. Tanks are built but have not installed the back baffle. I have been waiting for weather to warm up (no freezing overnight) before I fill my tanks with water and leak test them.

Cap off all fuel and vent ports, install fuel cap, and fill with as much water as possible. (maybe add food coloring). Put tissue paper on outside of tank rivet lines to "detect" any possible water leaks. Let sit 24 hours max?

Once successful I can drain, clean and dry tank before installing baffle. At this point I can do an air pressure test as recommended by vans (Balloon test?)

If that is successful, I will declare success until just before first flight when I will hopefully be able to test with 100LL (or whatever replacement comes out. HA!).

Don't have any way to store 100LL in my garage and don't want to put a large quantity of fuel in an open container (unfinished tank) for any length of time. Don't want all those gas fumes. Totally see the points others have made, but not sure it's practical (at least for my situation).
 
Guess I'm planning on bucking some of the advice given in this thread.
Currently I think I'm in about the same place as Roman. Tanks are built but have not installed the back baffle. I have been waiting for weather to warm up (no freezing overnight) before I fill my tanks with water and leak test them.

Cap off all fuel and vent ports, install fuel cap, and fill with as much water as possible. (maybe add food coloring). Put tissue paper on outside of tank rivet lines to "detect" any possible water leaks. Let sit 24 hours max?

Once successful I can drain, clean and dry tank before installing baffle. At this point I can do an air pressure test as recommended by vans (Balloon test?)

If that is successful, I will declare success until just before first flight when I will hopefully be able to test with 100LL (or whatever replacement comes out. HA!).

Don't have any way to store 100LL in my garage and don't want to put a large quantity of fuel in an open container (unfinished tank) for any length of time. Don't want all those gas fumes. Totally see the points others have made, but not sure it's practical (at least for my situation).

Brian, at least go to the grocery store and buy bulk RO water with less than 10 PPM TDS water, it will be the safest. Some ground water is so bad that entire communities use RO treatment. You can buy a TDS meter from freshwatersystems.com. Dasani bottled water is 125 PPM --to much. My local Kroger store has bulk-by-the-gallon water and it is 5 ppm.
 
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