Pressure Method of Leak Detection

[mcneon]

I've read on other motorhome sites about a blower method of water leak detection. As I understand it, you hook a fairly powerful and high-volume air source to a window of your trailer or motorhome, seal up all the openings as well as you can, and check for leaks by applying a soapy solution to suspect areas. Apparently it doesn't take a very high pressure differential or a very big leak to blow bubbles.

Has anyone on the forum ever tried this on an Airstream? I have an annoying intermittent leak near my MH doorframe, and this sounds like a very good way to find it. I'm wondering what kind of blower is adequate but doesn't cost a fortune, and how you might easily attach it to a window opening.

Bob McKeown

[wahoonc]

Bob,
The test unit in question is a pretty decent sized piece of equipment. The one I saw took air in from the roof vent and pressurized the interior of the RV. I was told they are expensive...around $4k or so I have no idea of the rating of the motor. May I suggest you locate a dealer that has one and have them run the test? BTW some SOB manufacturers website shows one...I just can't remember who's

Aaron

[Happycampers]

Hi Bob, We just located a water leak in our trailer by spraying a soap solution on the outside and using a small air compressor on the inside where the water was showing up and found the leak about 4ft away from where the water was coming in. Sounds like this would work for you too. Good luck. Marvin

[markdoane]

Here's a leak tester.
http://www.rvleaks.com/how.htm

I finally discovered a use for that old furnace blower.

[greg176]

Perhaps a shop-vac inside the trailer and taped up to one of the vents might work.You would have to tape up the plumbing and fridge vents too.

[wahoonc]

Originally Posted by markdoane

Here's a leak tester.
http://www.rvleaks.com/how.htm

I finally discovered a use for that old furnace blower.

That is the one I saw...but how much?

Aaron

[markdoane]

Originally Posted by wahoonc

That is the one I saw...but how much?

Aaron

Probably up to the dealer/service mgr. There are hundreds of locations listed on their web site.

[mcneon]

Greg176's suggestion makes me think that a leaf blower might do the trick. Those things put out a pretty high volume of air. They're not designed to work against a high outlet pressure, but that's probably not an issue with all the possible outlet points in my motorhome.

My notion would be to tape up my aged window and door weatherstrip, the plumbing vents, and maybe the door on my inverter compartment, and see what happens. Since I'd be pressurizing the interior, taping dry cleaning bags over the inside of windows, air conditioner, and such might work, too. I'm also thinking that, if one leaf blower didn't give enough oomph, adding a second or third might just do the trick.

Bob

[greg176]

I repair leaks in aircraft fuel tanks by going in the tank and applying a 2psi negative pressure to the tank and using bubble fluid to detect the source of the leak.Kids bubble fluid watered down works best.A big leak like you would have in a trailer would not take much pressure to detect.I plan to try the shop-vac as soon as I finish the skin replacement.I will be using a water manometer to measure pressure.
A word of warning .There is a good chance that you will cause more leaks than you fix by pressurizing your Airstream.
60" of water equals 2psi .I don't plan to try more than 12".

[RivetED]

That's an interesting approach to one of the more difficult problems to fix.

[markdoane]

Originally Posted by greg176

I don't plan to try more than 12".

I think I would go through about 10 rolls of duck tape before I could get as high as 12". Unless I had a nice jet turbine for a fan.

[greg176]

That 12" is very roughly .4 PSI and is probably a bit much for a trailer does 3" sound better (I do tend to exagerate).I do plan to give the shop-vac a try but it looks to be next summer some time.Right now it is not a problem to find leaks in the pouring rain here.The problem is keeping ahead of them.

[markdoane]

Originally Posted by greg176

That 12" is very roughly .4 PSI and is probably a bit much for a trailer does 3" sound better (I do tend to exagerate).

Greg,
I wasn't disputing with your choice of numbers. I was commenting on how much work I need to do yet.
I haven't got my windows reglazed, the door gasket replaced, the solardome remounted, wheel wells replaced . .
. . . . . .probably next spring for me.

[mcneon]

Originally Posted by greg176

I repair leaks in aircraft fuel tanks by going in the tank and applying a 2psi negative pressure to the tank and using bubble fluid to detect the source of the leak.Kids bubble fluid watered down works best.A big leak like you would have in a trailer would not take much pressure to detect.I plan to try the shop-vac as soon as I finish the skin replacement.I will be using a water manometer to measure pressure.
A word of warning .There is a good chance that you will cause more leaks than you fix by pressurizing your Airstream.
60" of water equals 2psi .I don't plan to try more than 12".

It sounds like you analyze those tank leaks while you're physically inside the tank, so I'm assuming you work on BIG tanks. My problem is that seeing bubbles on the inside doesn't tell me much about the source of the leak. I can easily see where the water comes out, I just can't figure out where it's getting in! (If a guy had just finished a floor replacement and had all of the interior skin off, the vacuum approach would probably be a wonderful way to find and eliminate leaks.)

I found some discussion on a GMC MH website about using a furnace blower as the pressure source. They use a length of 12" flex duct to connect to a vent window, and several people reported very good luck with that method. I have an HVAC blower cabinet in my shop, so I think that's what I'll try first.

If I find my main leak with this method, I think I'll test around every window and body seam while I'm at it. I'm concerned that, with a 30-year-old sealant job, there could be minor leaks appearing that might go unnoticed for a long time.

Bob

[greg176]

I was suggesting putting the shop-vac inside the trailer sucking in through the vent, that would pressurize the trailer.BTW those tanks I work in are usually in the B737 and just big enough for me to drag myself into.It's not pretty.