Finding Leaks

Winter in the Great Basin is when it gets wet. Usually. This year is off to a good start with some late November showers and even a bit of snow already.

This means that it is time to worry about leaks. An Airstream is a bit more resistant to leaks than many other RV’s because of its construction. But leaks can still happen. One source is from fixtures added to the outside that are attached with screws. These can be solar panels or even awning rails. Another source can be windows. The vista views in seventies Airstreams in particular have seal problems. Running lights may be another source of leaks.

Leaks can be difficult to find because the evidence, wetness inside, can be quite a ways removed from the source. One interesting method to find leaks has been developed into a product for RV dealers and repair shops by Sealtech Manufacturing Inc. – RV leaks bubbles recreational vehicles. What this does is to pump air into the RV and then soap down the exterior looking for bubbles as air leaks out.

You might be able to do something like this with a shop vac, some duct tape, and a bit of ingenuity to fix your own leaks. The first task would be to route the shop vac exhaust into the trailer. On an Airstream, this might be easiest using a piece of cardboard with a hole for the vac hose fitted into a storage hatch door opening.

The next task would be to plug the big holes. These would be the fridge vents (top and bottom) and the stove vent. Garbage bags covering the vent and taped around the edges might do the job.

At this point you can start filling the mouse holes. Expanding foam might do for some cracks. Sealed patches might do for others. Caulk for others.

A decent sized shop vac will push enough air to build up a bit of inside pressure despite a few small holes. The Sealtech product claims it has a pressure control but it is hard to see how any air source that runs off a standard 110v circuit could build enough pressure to cause any problems. To be sure you could add a water manometer, such as used to determine gas pressure to your stove and furnace, to the air entrance fixture. Keep in mind that simple fans have been used to pressurize the insides of collapsable buildings to hold up the roof. It shouldn’t take much air in an RV to get air flowing out through leaks.

Once all the visible holes have been patched or covered, it is time to start seeing if you can blow bubbles. A bit of dish soap in a spray bottle of full of water is the tool here. And there is a skill involved.

Soap Bubble Testing

The oldest method of leak detection, soap bubble testing, is simply the observation of a pressurized component that has been sprayed or brushed with a soapy solution. Soap bubble testing can detect very small leaks allowing the operator to pinpoint the exact location of a leak. However, the process is highly dependent on the skill and patience of the operator. This can be a factor if the operator’s perspective is limited. For example, small leaks may remain hidden on the reverse side of a component or in a recess. This is a common occurrence in the aerospace industry where components are usually packed into tight spaces.

Another consideration when using soap bubble testing is that sometimes larger leaks do not cause the formation of bubbles. Instead, the compressed air blows away the soap solution, and the inspector may fail to observe such a leak.

Another factor to keep in mind is that with small holes, the capillary force can be extremely strong. The result is that liquid that has been sucked into a micro leak by capillary action, cannot be forced out with compressed air, and therefore no bubbles will appear. Ensuring Leak Integrity in the Aerospace Industry – November 2005 Issue – (Aircraft Maintenance Technology)

To find out a bit more about leaks, check Big Blu Manual 4 classifies six different kinds of leaks in refrigeration systems. If soap isn’t good enough for you, see Leak Tec – Thin Film Bubble Testing Solutions and find out about the technology involved. For an example of leak detection and repair, see How to Fix a Leak … in the HULK!

Will this idea of pumping air into an Airstream to find leaks work? Don’t know. Haven’t tried it, yet. But it sounds good, shouldn’t cost too much to try, and would only take a bit of time. What do you think?

UPDATE: One notes that you need to plug the sinks and drains so as to not blow air out through the gray waste tank. This shouldn’t be a problem with the black tank unless you have a sink that drains directly into it. Another notes that a big squirrel cage fan, such as used in swamp coolers might be a way to get pressure inside. Others note that a Fantasistic Fan might move enough air to work for this purpose.

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