Tami and I finished sealing the rear baffle plate on Monday.  So today (Saturday), I decided to pressure test the fuel tank to see if my tank sealant days were over.  As I did with the right tank, I set up a tygon tubing manometer to monitor the tanks ability to hold a slight air pressure.

The idea here is that when you pressurize the fuel tank with low pressure air, the air will push on the water in the tygon tube and in this case, push the water up the 4" x 4".

I just secured the tygon tubing to the 4" x 4" and jammed a funnel at the top so that I could pour in the food colored water.

Using a manual bicycle air pump connected to a schraeder valve in the tank drain fitting, I pumped air into the fuel tank until I had approximately 20" in difference in the 2 column heights of water.  I marked the height of the water, the time, and the temperature.   A one degree change in room temperature was resulting in a change of approximately 1" in the height of the column of water.

After I initially placed pressure on the tank, level was very slowly lowering.  Ooh GREAT, my worst nightmare has come true, a leak that will be a pain to fix.  However, before I get to negative about the whole thing, I decided to check the fuel tank cap since it is a pretty big hole.  I have the more expensive locking fuel caps and the first tank gave me no problems.  Anyway, I see that their is a nyloc nut on the inside of the cap that controls the amount of pressure exerted on the cap and flattening a rubber washer.  I decided to tighten that up just a hair (I ended up turning it about "1-flat" on the nyloc nut).  I re-installed the cap, re-pressurized the tank and voila.....  The manometer was holding steady ...

I just sat a thermometer near the tank so that I could keep an eye on the temperature vs. water column height.

UPDATE:  I checked on the fuel tank the next morning (20 hours +) under pressure and the manometer level only varied a inch or so and this morning, it was higher than when I marked it yesterday.  I am going to call the tank good...

After I decided the tank was sealed, I removed all the manometer hardware and installed the tank fuel drain.  I torqued the fuel tank drain to 60 in-ibs.  As soon as I get some other miscellaneous wing stuff done, the tank will be ready to install on the wing.

I opted for the deluxe locking fuel cap when I ordered my wings.  I am extremely happy with the quality of these filler caps.

Now that my tanks are more or less done, I can work on a ton of other miscellaneous wing stuff I need to complete so I can get started on the fuselage.

When I got home from work tonight, my eagerly awaited order from Aircraft Spruce was sitting in the garage.  I did end up breaking down and ordered a cheap rivet cutter.  While I was ordering from Spruce, I got some hand protector cream, and a bunch of AN fittings.  When I ran a fuel return line back to the tank, I had to steal kit parts from the left tank so I ordered a bunch of AN fittings to replace the ones I used and to more or less put together my "starter kit" of fittings.

I had ordered the ez-turn lubricant in anticipation of fuel tank testing.  In addition to a lubricant, anti-seize material, it seals threaded connections.  In the background, are the AN fittings needed to cap off my tank penetrations.  The brass looking component is a schraeder valve (like the air valve on your car tires).  That was part of Van's fuel tank testing kit and is threaded into the tank drain connection to allow you to place the fuel tank under a slight pressure.

Here you can see my vent line and fuel return line bulkhead fittings.  I just used some 1/4" tygon tubing and a hose clamp in order to make a makeshift manometer.  Before putting the tygon tubing on the fuel return line, I gooped the threads with the ez-turn lubricant.  A number of builders have stated that they couldn't get a good seal at this connection as the tygon tubing wouldn't seal around the threads.  Lubricating the threads worked GREAT.  I torqued the -4D cap fitting to 45 in-lbs and I torqued the -6D fuel pickup cap to 80 in-lbs (which are at the low end of their torque ranges).

I didn't have any leaks at this connection.

This is more for my records, but this was the temp in the garage at the fuel tank.  Temps in the area are supposed to get in the low 90's and just a couple of degree swing in the garage is showing an effect on the water height in the tygon tubing.

Here is an overall picture of my manometer setup.  I used some RED food coloring to give the water a high color contrast in the tube.  NO, your manometer tubing doesn't need to be as high as I have it in the picture.  I just didn't want to cut my 10' length of tubing.

Below, is the schraeder valve I mentioned earlier threaded into the tank drain fitting.  Just put a tire pump on this fitting and pressurize the tank until you get a difference in water column height in your manometer.

In Van's book "21 years of the RVator" (page 69), there is an article about pressure testing the fuel tank.  In that article, it mentions that pressure in the tank should stay below 1 psi.  Using an air compressor to apply pressure to the fuel tank could result in over pressurizing the fuel tank that I have WAY TO MANY HOURS IN.  Therefore, I just used a bicycle pump.  It only takes a couple of strokes of this little bicycle pump to get the desired height difference in the manometer.  1/2 of a stroke on this pump gave me over an 1" of height change.

I had some "Snoop" laying around the garage so I snooped all the rivets, fittings, etc. until I ran out.  NO IDENTIFIED LEAKS YET!!!!

Although I didn't get any leaks around my fuel filler cap with the snoop, I was seeing a change in water column height, so as a precaution, I duct taped around the fuel filler flange.  In retrospect, I think that it was just the air entrapped in the manometer that bubbled up and out of the manometer.

Here is a blurry picture, but I pumped up the fuel tank until I had a difference in water column height and I marked it on the wing stand with the time.  I marked the line at 8:30 pm and I snapped the picture almost 2 hours later.  IT IS LOOKING REALLY GOOD FOR NO LEAKS!!!!

I will leave this setup overnight and see how it does.  I am running the air conditioner in the garage so temperatures should remain within a degree or two during the pressure test.  I am also marking indications taken from my altimeter to monitor atmospheric pressure changes so that I can reconcile any changes in water column height.