This report covers:

  • Leaked down
  • Leaking air hose
  • Gotcha!
  • The cobbler’s children have no shoes
  • Time to get around to it
  • How to find the leak
  • Disassemble the leaky connection
  • Applying Teflon (plumber’s) thread-sealing tape.
  • Teflon (plumber’s) tape
  • Did it work?
  • And the rifle?
  • Summary

If there is a fear when buying a precharged pneumatic airgun for the first time, it’s that it will leak. Today we look into that concern in a different way.

I was at the firearms range last Friday, testing the Makarov pistol and another pistol that I will tell you about soon. I also took along the Umarex Gauntlet .30 caliber, because, as I discovered in Part 1 of that series, this rifle is really a big bore that’s too loud and too powerful to shoot in my house.

Leaked down

I had aired up the rifle about four days earlier, knowing that I would be going to the range on Friday. But when I packed it to go the day before I noted that it had leaked down. So it went from full to empty in about three days. No problem, however, because I had just filled both my carbon fiber air tanks with the Air Venturi compressor.

Leaking air hose

I took the 88-cubic foot tank to the range. I knew its microbore air hose (small diameter to waste less air when uncoupling) had a leak at the coupling that attached to the rifle, but once the pressure got past 1000 psi, the leak stopped.

Gotcha!

At least that hose leak had always stopped before. At the range when I tried to air up the Gauntlet reservoir the air never stopped leaking and would not put over 1000 psi into the rifle.

The cobbler’s children have no shoes

There I was — at the rifle range and all set to get material for three blogs when one of them just evaporated before my eyes. And it was my own fault. I had been runnin’ and gunnin’ (literally) for months with that leaky hose, knowing I had to fix it, but I could not ever find my round tuit. [Note for our readers outside the US and Canada — this is an expression we lazy Americans use, “I’ll fix it when I get around to it.”]

Find a Hawke Scope

Time to get around to it

Well, circumstances had pushed me into a corner. It was time to get around to it, and I thought some of you who fear the dark side of airgunning, as precharged pneumatics are often called, would like to watch. Besides, if I’m going to take the time to do something like this, I really need to get a blog out of it.

How to find the leak

The best way to find a slow leak is to put soapy water on the suspect connection and watch for bubbles. That will show you precisely where the leak is located. But my leak wasn’t slow. It was so fast that I could hear it and feel it by wrapping my hand around the connection. Let me show you.

hose connection
There was no question this was the leaking connection. Putting my hand around it, I could feel the air leaking out.

Disassemble the leaky connection

The first step was to disassemble the leaking connection. When I did I saw that both threaded sides of the interconnecting black piece had no Teflon tape on them. Neither was there any tapered connection that’s sometimes found. No wonder it leaked!

connection apart
As you can see, the black piece that connects the female Foster connector on the right to the hose connector on the left has no plumber’s (Teflon) thread-sealing tape on it’s threads on either side. The small white band that you see on the left side of this connector is old plumber’s tape that has been wadded up and pushed forward into a smaller non-threaded portion of the connector.

Applying Teflon (plumber’s) thread-sealing tape.

To seal the threads you wrap at least three windings of plumber’s tape around the threads. The direction in which you wrap it is vital to your success. Because you are putting one part into another and twisting them together until the threads bottom out, you have to wrap the tape the right way or it will peel itself off as the parts are threaded together. If the threads are wound clockwise (right-hand twist — the most common way) the tape should be wound on counter-clockwise. That way the threads of the connecting device will try to tighten the tape as the parts are threaded together. Clockwise and counter-clockwise are when looking at the connector from the end you will be connecting to.

I didn’t bother removing the old tape because it wasn’t doing anything anyway. I just wound on three turns of fresh tape.

connector taped left
The left side (hose connector side) of the adaptor has been taped. Until I saw this photo enlarged I didn’t realize there was an o-ring on the right side. It didn’t work, so who cares?

Once the black adaptor is screwed tight to the hose connector, I wrapped the right side, that attaches to the female Foster fitting. I didn’t see the o-ring so I didn’t do anything about it, except to tape over it.

connector
I taped the threads on the right side next and went right over the o-ring that I didn’t see.

Teflon (plumber’s) tape

The Teflon tape you get at the hardware store. It has no sticky side. You apply it under slight tension, so that it stretches just a little. It clings to itself after being applied and once the parts are screwed together it won’t come apart. As long as you wind it on correctly, it should last for many years.

Teflon tape
Teflon tape is also called plumber’s tape.

Did it work?

The test for whether it worked is to connect to something and try to inflate it. Since the .30 Gauntlet was also a leaker I decided to use it for this test. That gave me the opportunity to try to fix its leak. Or at the least I could determine how long it took to leak down.

The hose is completely sealed after the fix. I left it at max pressure (4,500 psi/310 bar) for several seconds and saw no decline in pressure on the tank gauge.

And the rifle?

One thing I did to help the Gauntlet stop leaking was introduce a drop of silicone chamber oil as I filled the rifle. Here is what that looks like. Use high flashpoint silicone oil only for this, as petroleum-based oil can ignite and explode under high pressure!

silicone oil
I put a drop of silicone oil on the filler nipple to be blown into the reservoir at filling. Use high flashpoint silicone oil only for this!

I filled the rifle and took note where the onboard gauge needle stopped, which was two hashmarks into the green portion of the gauge. I will watch this over time and see if the rifle is still leaking. If it is, is the leak slow enough that I can still test the rifle?

Summary

Today you got to look behind the curtain when things didn’t go right. Since this was while testing a PCP — the so-called dark side of airgunning — I thought you’d like a look at what goes on.