Fuel tank pressure testing helper!

[Brantel]

For anyone that has struggled to seal the tank fill fitting when pressure testing your tank, this little puppy works perfectly and is $8 at Lowes. Be sure to monitor how much pressure you use because this dude ain’t gonna give like a glove, balloon or condom! I will be using a digital manometer and a small hand pump.

 

[sc_pilot]

I wonder if you could modify that with a fitting to attach a balloon too. Like a barbed fitting drilled in the center plate. Great idea, I have tons of these at work. I’ll look into this since I just did the inspection port mod.

 

[Brantel]

I wonder if you could modify that with a fitting to attach a balloon too. Like a barbed fitting drilled in the center plate. Great idea, I have tons of these at work. I’ll look into this since I just did the inspection port mod.

Yeah, might be doable! Just keep in mind, balloons leak air like crazy!

 

[sc_pilot]

Found that out with a rubber glove I tried using. I switched to a plastic bag and had better luck. Although it was harder to seal around the tank filler neck.

 

[rv7boy]

Brian, since you posted this in the -12 forum, I assume it is only useable on the -12 tank. But since it now appears on the VAF Front Page, builders of other models (including me) will wonder. So did you use this also on the -7 you built? Or can you offer an opinion on its possible use on a “non -12” tank?

 

[Brantel]

Brian, since you posted this in the -12 forum, I assume it is only useable on the -12 tank. But since it now appears on the VAF Front Page, builders of other models (including me) will wonder. So did you use this also on the -7 you built? Or can you offer an opinion on its possible use on a “non -12” tank?

I did not use it on the 7. Not really sure there is an application for it on the traditional wet wing models.

 

[lr172]

good idea. I just accept the leak there. I use the leak down compression tester tool and a manometer. This allows you to still get a consisten pressure even with the leak at the cap.

 

[Brantel]

Now the rest of the story!

Figured I owed the group a follow up on this plug I used to pressure test my fuel tank....

So this plug from Lowes is designed to pressure test household plumbing......
The only problem is that it leaks like a screen door around the center bolt. I tried everything to stop the leak. Put grease on the seals and everything else I could think of. Nothing helped!

Then I had an idea....

I cut a balloon and then stretched it over the fuel filler neck. Ensured there were no creases or wrinkles and then shoved the plug into the filler neck and tightened. This worked perfectly! Stopped the leak path up thru the center of the plug. The balloon conforms to the shape of the inside of the plug and forms an air tight membrane.

I used an old fashioned U tube water manometer and a digital manometer to monitor the pressure in the tank. After three days of watching the pressure, I declared it leak free. The ambient temp and baro does cause the pressure to rise and fall but on consecutive days I checked it at around the same temp and corrected for the minor changes in baro and the pressure remained constant. I also soaked the tank several times in soapy water looking for any bubbles.

Success!

Kinda strange that something designed for pressure testing leaks......


Edit: Added some clarification to the original post in blue

 

[rvbuilder2002]

The ambient temp does cause the pressure to rise and fall but on consecutive days I checked it at around the same temp and the pressure remained constant.

Anyone using this leak check method should keep in mind that ambient pressure will effect the indication also.
A change in BARO will cause the indication to go up or down like an old fashioned weather forecasting instrument.

Did your fuel tanks test "FAIR or STORMY"

 

[lr172]

Figured I owed the group a follow up on this plug I used to pressure test my fuel tank....

So this plug from Lowes is designed to pressure test household plumbing......
The only problem is that it leaks like a screen door around the center bolt. I tried everything to stop the leak. Put grease on the seals and everything else I could think of. Nothing helped!

Then I had an idea....

I cut a balloon and then stretched it over the fuel filler neck. Ensured there were no creases or wrinkles and then shoved the plug into the filler neck and tightened. This worked perfectly! Stopped the leak path up thru the center of the plug. The balloon conforms to the shape of the inside of the plug and forms an air tight membrane.

I used an old fashioned U tube water manometer and a digital manometer to monitor the pressure in the tank. After three days of watching the pressure, I declared it leak free. The ambient temp does cause the pressure to rise and fall but on consecutive days I checked it at around the same temp and the pressure remained constant.

Success!

Kinda strange that something designed for pressure testing leaks......

manometer reading will fluctuate based upon temperature AND barometric pressure. So if readings were consistent with same temperatures AND a drop in barometric pressure, that would indicate a leak. when leak testing with water based manometer, you need to adjust for both temp and baro pressure. unsure how a digital one works.

 

[Brantel]

unsure how a digital one works.

Works the same way….it has another port open to atmosphere.

 

[Brantel]

Anyone using this leak check method should keep in mind that ambient pressure will effect the indication also.
A change in BARO will cause the indication to go up or down like an old fashioned weather forecasting instrument.

Did your fuel tanks test "FAIR or STORMY"

Yea, should have mentioned that I was also tracking Baro for my area during this time as well.

My tank tested “FAIR”

 

[Plummit]

Kinda strange that something designed for pressure testing leaks...

Not really. These are used to test drain and vent pipes with water pressure, not air. We called them "Dollar Plugs" in the plumbing industry, but I used them more often to plug a drain line clean-out when the threads rusted away and I couldn't use a regular raised-head plug.

-Marc

 

[henrysamson]

I had issues sealing the rubber glove then I did this:

A thick and wide rubber band around the neck that fit snug with one wrap.

The rubber glove, make sure there are no wrinkles.

A second rubber band.

Then the hose clamp vans supplies to install the tank. I tightened this down really snug.

Sealed perfectly for days. Yes, I did get some barometer effect.

 

[jhrubos]

balloons

a bag of 15 balloons is $1.00 at walmart