If you ask most people how to check for leaks in a kayak, the most common answer is probably to put the boat up on saw horses, fill it with a bit of water, slosh it around and look for drips. There’s a place for this method for sure, but it’s quite slow and hard to pinpoint exactly where a leak is coming from.
Another less common way is to use low pressure air, along with soap and water, and look for bubbles just like you would do when checking a leaky tire on your car or bicycle.
One challenge with this latter method is how to pressurize the hull. I did just this very thing today, and thought I’d share what I came up with. Though my method may not be unique, I didn’t come across it in my couple minutes of searching online before beginning.
On the weekend I picked up two rubber VCP (Necky) oval hatch covers to replace my very aged and cracked ones. One was good enough to keep around as a spare, while the other was certainly done for. I decided to try and use the one destined for the garbage as a “pressure testing cap” for the bow and stern hatches. I liberally applied contact cement all over both sides of the hatch cover to try and seal any cracks or slight porosity. After drying for an hour or two I drilled a 1/2" hole and stuck a tubeless tire valve stem (valve core removed) in the hole with a bit more glue. The whole thing was a bit Micky Mouse, but when I installed it on the boat and used a bicycle tire pump to add pressure I noticed the cover bulge out slightly before slowly settling back down. I grabbed a spray bottle with soapy water and went to work spraying down potential leak areas.
In the picture I’m using an old day hatch cover that I replaced with a SeaLect one a while ago. So far I found that the two rear bulkheads are leaking enough to produce vigorous bubbles with this method. I wasn’t able to find any external leaks, but I’m going to reseal the bulkheads with silicone and then repeat the procedure to find any smaller leaks in fittings, deck, or hull.
I’m also going to try this on a plastic boat for which I don’t have any hatch covers I can bastardize. I’m thinking to try using a plastic bag along with some tape, elastic bands, and other paraphernalia to produce a seal on the hatch for pressurizing.