DIY Pressure Testing for Rain Leaks
I have an impossible to find leak in my travel trailer and I am at my wits end. My trailer is a 40 ft. Park model on a permanent campsite in southern Delaware with a hard room and deck attached so I d...
Forum Discussion
Please bear with me while I attempt to clear up the confusion mentioned by Togger regarding the various blowers described in this thread that have widely different air flow capacities (300 CFM to 7,000 CFM).
All that any of us DIY'ers, as well as SealTech, are trying to do with our blower is to create an air pressure inside the RV that is slightly higher than the air pressure outside. This difference in air pressure causes air to flow out of any leak points, that are then located by spraying a soap solution onto seams, seals, etc.
We prepare for the leak test by closing windows, doors and roof vents, and taping closed obvious large leaks such as the stove vent, etc. By doing this, we make our RV into a pretty tightly sealed container, meaning that not a lot of air can leak out.
Using a 7,000 CFM blower to do a leak test doesn't mean that that blower will actually push 7,000 cubic feet/minute of air into the RV. If it was really doing that, then there would have to be a huge leak to let the air back out, such as an open window. What really happens in these tests is that the blower pushes in just enough air to make up for the total amount of air that is flowing out all of the leaks. The amount of air flowing out the leaks is the result of the elevated pressure that be blower is creating inside the RV. Higher pressure causes higher air flow out the leaks.
Please look at the SealTech operating procedure I quoted in my previous post above. In Step 2 they adjust the RPM of the blower to set the pressure, not the air flow rate. They aren't looking for a high flow rate, just the desired pressure range.
As an aside, I found their note in Step 4 to be interesting. Pinhole leaks require higher pressure while large leaks require low pressure. Why? My interpretation is that a pinhole will have a very low airflow and might not make a noticeable bubble unless the pressure is high enough to create a large enough air flow. On the other hand, high airflow through a large leak will just blow the soap solution away without forming any bubbles. A lower pressure reduces the air flow, thus allowing large leaks to create bubbles.
All that any of us DIY'ers, as well as SealTech, are trying to do with our blower is to create an air pressure inside the RV that is slightly higher than the air pressure outside. This difference in air pressure causes air to flow out of any leak points, that are then located by spraying a soap solution onto seams, seals, etc.
We prepare for the leak test by closing windows, doors and roof vents, and taping closed obvious large leaks such as the stove vent, etc. By doing this, we make our RV into a pretty tightly sealed container, meaning that not a lot of air can leak out.
Using a 7,000 CFM blower to do a leak test doesn't mean that that blower will actually push 7,000 cubic feet/minute of air into the RV. If it was really doing that, then there would have to be a huge leak to let the air back out, such as an open window. What really happens in these tests is that the blower pushes in just enough air to make up for the total amount of air that is flowing out all of the leaks. The amount of air flowing out the leaks is the result of the elevated pressure that be blower is creating inside the RV. Higher pressure causes higher air flow out the leaks.
Please look at the SealTech operating procedure I quoted in my previous post above. In Step 2 they adjust the RPM of the blower to set the pressure, not the air flow rate. They aren't looking for a high flow rate, just the desired pressure range.
As an aside, I found their note in Step 4 to be interesting. Pinhole leaks require higher pressure while large leaks require low pressure. Why? My interpretation is that a pinhole will have a very low airflow and might not make a noticeable bubble unless the pressure is high enough to create a large enough air flow. On the other hand, high airflow through a large leak will just blow the soap solution away without forming any bubbles. A lower pressure reduces the air flow, thus allowing large leaks to create bubbles.
