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 do not have the option to take it in to a dealer to have a Seal Tech leak check performed.

I am determined to take matters into my own hands and figure out how to do my own pressure test on site. After searching various posts from the past, this is my basic plan.

I am going to purchase a high CFM air moving device, probably a carpet dryer, and rig it up to blow air through the side storage hatch door which is under the bed in the bedroom. I will lift the bed so the air can enter and pressurize the entire camper. To achieve a tight camper I will tape off the sink drains, shower drain, kitchen exhaust, and any roof vents.

Using cardboard and duct tape I will seal the carpet dryer fan into the camper hatch. I will insert a 1/2 inch clear plastic tube through the cardboard so it runs from the inside to the outside. On the outside this tube will be taped to the camper in a U-shape about 1 ft. High to serve as a homemade manometer to detect air pressure. I will pour water into this tube enough to fill the bottom few inches of the tube.

When I start the fan I will know I have achieved positive pressure on the inside of the camper if the water levels become uneven on the two sides of the plastic tube at the bottom of the U. Adequate pressure should range from 1/4 to 1" difference in water height between the two sides.

I don't want to damage the camper with too much pressure so I i will start the fan with a door cracked and then slowly close the door while checking that I don't get over 1" pressure in the manometer.

Once I have achieved pressurization, I will spray all possible leak areas on the outside with a strong solution of dish soap and water in a pump-up sprayer. I expect to see bubbles forming anywhere air is escaping and this is the exact spot water could be entering. I will mark any bubbling areas, repair them, and then re-check afterwards to make sure they are sealed.

I am looking for advice from anyone who has done this type of test. Here are my questions:

1. How much CFM of air will I need to get adequate pressure. I am looking at purchasing a powerful carpet dryer this settings from 2500 to 4200 CFM. I figure if overpowered I can simply reduce pressure by cracking a window or door. If I am underpowered I am setting myself up for failure. Keep in mind this is a 40 ft. Trailer.

2. I am planning to do the test with 2 large slide-outs in the open position. Would the air seal be better in the closed position? I will be testing prior to campground turning on electric for the season so will use a generator for power and may have trouble if I need to close the slides.

3. Do I need to open something to allow air pressure to build between the trailer ceiling and trailer roof. If so, they would also need to do this when performing a Seal Test pressure test.

4. Is there anything I have wrong or am missing?

All advice appreciated! Thanks!

Explorer1016
Explorer
Mar 14, 2015
Here is a link to my pressure test back in February. It takes the right equipment to do a pressure test correctly and with noticable results. You will have to scroll through the pages to see my pictures.

http://ww.rv.net/forum/index.cfm/fuseaction/thread/tid/28174200.cfm
westend
Explorer
Mar 14, 2015
Answers:
1) Incalculable because we have no idea what pressure the carpet dryer achieves. It's also not that technical. If the blower moves enough air, the test will be good. Remember, if you're raising the pressure 1" of water column, you're raising the pressure 1/14 of what's already there.

2)I would guess that the seals might hold better in the closed position. If you want to test with the slides open, it doesn't take a whole lot of effort to tape the slide sealed back to the siding. I use masking tape for sealing vents drains,etc..

3)No, those cavities will be pressurized, also.

4) Your process seems spot on. It is a lot easier than one would think, I wouldn't worry about too much pressure, your doors will be leaking, even when shut.
CloudDriver
Explorer
Mar 14, 2015
A large air flow isn't what is needed to do a leak test, especially as you are sealing off the vents, drains, etc. What is needed is a blower that will produce about 1 inch of water pressure. That's not much pressure (about 0.036 psi) but I have no idea whether a carpet dryer would do that. I was able to produce 0.6 inches of water in our MH with an electric leaf blower and the dash fan on full.

A few years back I found the operating instructions for the SealTech system online and copied them in case I needed to do a test myself. Here's what they recommend for test pressures:

Note: normal operating pressures range from 0.3 inch to 0.6 inch water column. If initial pressure with impeller at maximum RPM is less than 0.4 inch, additional preliminary sealing of RV should be undertaken. A walk around the exterior of the unit will usually disclose causes of major air escapement, (indicated by outrushes of air) which can then be corrected.

1. With door closed, turn on fan unit switch. Vary RPM to determine that pressures are within operating parameters noted above.
2. Set RPM to produce differential pressure of 0.3 - 0.5 inch water column (subject to 4. below) exit the RV, closing and securing door.
3. Spray soapy solution to all exterior areas where leaks are likely to be found and note location of faults. Judgement is required; for example, Pittsburgh seams will permit air escapement, but not all resulting bubbles will be indicative of a leak due to the seam overlap. However, where bubbles appear in a Pittsburgh seam at a junction with the leading edge of a window or other outer skin break, rain water could be forced in by air pressure arising from highway travel.
4. Note: Larger leaks require lower pressure than small leaks. Pinholes may require up to 0.6” water column; big holes as low as 0.15”.
John_Joey
Explorer
Mar 14, 2015
Very impressed with your logic and creativity. What I would do to ease some fear is to make sure the stove vent is not snapped closed.

If you indeed buildup so much pressure then the vent will act as a pressure release valve. It will also give you a heads up if the pressure is that high or not. Might want to take the screen out to make it even more effective.
pianotuna
Nomad III
Mar 14, 2015
Hi,

The fantastic fan set to suck air in was enough to give me a sensation of pressure on my ears. If you happen to have one--try it first?

Bubble soap from a dollar store may be useful.
westend
Explorer
Mar 15, 2015
I have no idea what my furnace blower that I use puts out in CFM. With the blower sealed into a window and all of the interior closed up as outlined above, my DIY manometer showed a pressure rise of about 1"WC.
Blower mounted in exterior window:

DIY manometer:

A pinhole leak in seam:
j-d
Explorer II
Mar 15, 2015
Mu two Fantastic vents would not produce enough to cause bubbles at a known leak.

I've been in my coach when tested with SealTech. We could enter and close the door without sensing overpressure in our ears. As soon as we left the coach and closed the door, SealTech had it back up to a pressure which would produce bubbles. Even with no special pre-sealing and the range vent open.

Manometer could simply be a "U" of tubing, half inside the coach and half out, right? Then mark initial level at zero and look for the water to rise about half an inch, less then one inch?

CD, any idea how hard I've looked for that information?!?!? You continue to amaze me.

Doggone!!! I've finally found the ONLY reason I didn't run 50A service out to the coach. I could have a pile of used HVAC blowers tomorrow. To get one that runs on 120VAC means a furnace has to be the donor. The A/C techs also tend to keep them to ventilate attics while they work.
westend
Explorer
Mar 15, 2015
Manometer could simply be a "U" of tubing, half inside the coach and half out, right? Then mark initial level at zero and look for the water to rise about half an inch, less then one inch?
No need to have the tubing half inside and out. If you place the tubing on a board as in my picture and have the tubing enter the structure close to the blowing device, you will have a measure of the pressure rise compared to the exterior natural air pressure. That measure (close to the device) will probably be at the highest measurable rise for the interior pressure.
CloudDriver
Explorer
Mar 15, 2015
j-d

Here's a link to the complete setup and Operating Instructions from the SealTech site. The page has a link to a pdf, so you can easily save them to your PC for future reference. I'm actually surprised that they post the pressure info for DIY types to make use of.
j-d
Explorer II
Mar 15, 2015
CD, I was actually on their site trying to sniff out the instructions. You clearly have the better sniffer. GOOD ON YOU!

I've thought of making either a window-mount like Westend's or a ST clone that mounts on the interior side of a roof vent.

We have a bathroom vent that's more PITA than it looks like to dismantle. And two Fantastic Vents that according to the .pdf from ST might actually be easier.

Westend, what are the details on your blower? I can see Dayton (Grainger) on it, but I take it to be a bought blower not something out of HVAC or furnace.