C-Forum

I have a Mohawk float bag that leaks but I can't locate the hole. I've sprayed with soapy water and tried submersing the bag in a lake.
Any other ideas are appreciated
Thanks

Put air in it & submerge it. Don't fill it up or you won't be able to submerge it easily.

I find leaks by filling up the air bag as full as I can get it in a quiet spot and then putting my ear to it as a press it hard against the floor. You can hear the air escaping from even the smallest pinhole. Once I locate the general area where the pinhole is, then I try to feel it on my face as I continue pressing down on the bag. I've had better luck with this method than immersion.

I have used all of the above-mentioned methods for finding leaks, and have had each one work, at least once.

The first thing I would do is carefully check the dump valve and the filler tube, both at the Roberts valve at the end of the filler tube, and the flange of the filler tube that is bonded to the bag. In my case at least 80% of the leaks were at one of those locations.

Checking the Roberts valve is easy. Just immerse the end of the filler tube in a glass of water and squeeze the partially inflated bag. Sometimes a little crack develops at the "elbow" of the filler tube near the junction of the bag. Sometimes you have to stress the filler tube a bit by wiggling it around to demonstrate a leak at the flange or at the elbow of the filler tube. I find it is usually pretty easy to partially inflate the bag and immerse the dump valve and filler tube in water in a bathtub to demonstrate a leak in those locations.

Good suggestions.

I too have found finding leaks in air bags not an easy task.

What about filing an air bag with coloured air (like a smoke marker)?

I've had some success in the past (with a Mohawk bag, no less) by holding it up against a bright spotlight in an otherwise completely dark space. Any irregularities in the material really stood out.

If you don't find the leak around the valves, then next check out the seams. After that check out your boat. Feel along the underneath side of the gunnels and anywhere a rivet, screw or sharp end of plastic gunnel material might rub against your bag, then check out the corresponding spot on the bag.

I agree with pblanc. The fill tube junction or valve is often the culprit. If it's not that then there's usually a pin hole somewhere on the top of the air bag. My preferred method is to fill be bag fairly hard with air then go over the entire top of the bag with my lips close to the bag. Your lips are real sensitive and can feel the slightest air leak. The seam is sometimes the cause if it's a defective bag.

Paddle Power wrote:
What about filing an air bag with coloured air (like a smoke marker)?

If you're on good terms with your friendly neighborhood auto mechanic, there is a tool that does just that- used for finding leaks in a car's evaporative emissions system. I suspect it would work perfectly.

Put soapy water INSIDE the bag thought the dump valve (you don't need much), then blow it up all the way. The easiest and most sure-fire way to find leaks I've used. Draining the water through the hose when you're done isn't too hard either.

Thank you to everyone for your ideas. I'll give them a try as soon as it warms up a little here in Kansas.

RodeoClown wrote:Put soapy water INSIDE the bag thought the dump valve (you don't need much), then blow it up all the way. The easiest and most sure-fire way to find leaks I've used. Draining the water through the hose when you're done isn't too hard either.

That is so smart. Why didn't I think of that?

If it is not the valve or fill ring area, try using scrubbing bubbles bathroom cleaner. Sometimes it won't "bubble up" if ther is not enough pressure as well. Spray on and push down on the bag. Sounds like the holes are so small you need to add a fair amount of pressure to make them show.

I'm riffing on pblanc's idea, just a little more emphasis.

If you air fill the bag up and squeeze, or even use water, you will be pressure "sealing" a leaky flange against the material and stopping the leak, eliminating the presence of same.
As a preventative measure I shoe goo the base of the tube to the bag. Looks like crap but stops it from flexing. Also a tube hanging loose in the wind for a 60 mile shuttle is taking more abuse than a several years of paddling rapids.

My last couple of sets of float bags were Harmony and the fill tube is near the grommet at the middle of the big end. I made loops of small diameter shock cord to restrain them when in transit.

When I was regularly paddling my Zephyr and leaving the bags in, I took some extra Coroplast I had and made bag protectors :



Overkill? Maybe, but it only takes a minute or two to put them in / out and they don't take up much space.