Inflatable kayak valves, PRVs and pumps

IKvalvesThe best inflation valves for an IK aren’t the simple plugs you find on an airbed, but the high-pressure one-way valve as found on white water rafts, pictured right and copied by many. Like a car tyre valve, one-way operation is the key so what pumps in won’t rush out when you remove the inflation hose. Not like the twist valves on a Feathercraft Java or an Alpacka, or even the more basic bungs of an old Semperit IK.
pump-barrelgrabvalveWith proper valves, pushing the button down and turning clockwise locks the valve open to release air when rolling up. Then, for pumping up push lightly and turn anticlockwise to release the valve so it springs back up to seal. This closed ‘button up’ position is the best way to transport an IK as the valve mechanism is less vulnerable to damage. To lose a little pressure (say, the boat is getting hot in the sun) just jab the valve core button, same as on a car tyre. The new Gumotex valves are even easier ‘push-push’ valves to lock open or close. valvespannerI always make sure I refit the cap straight away to keep grit or water out. grabtoolThese types of valves have been reliable on all my IKs although this Gumotex 410C owner didn’t find that. Old Gumotex valves are slightly cruder versions of a Halkey – newer ones are easy to use push-push types. Once in a while – or after the boat is new – you may want to check the valve is screwed tight against the fabric with the valve spanner, right. They’re useful too for removing the valve (or a PRV, below) should it jam or play up.
valve-bostonPush-fit, screw-cap Boston valves (left) are used on cheaper IKs as well as £25  slackrafts. They use a simple soft rubber ‘mushroom’ on a stem for the one-way element and so can only handle lower pressures. In a way, they act as their own pressure relief system. As shown left, the whole body including the flap valve can be unscrewed to fully deflate a boat.
pump-bayopush-fitadapterWhen it comes to inserting the inflation hose, some IKs like old Gumotex have simple push fit valve bodies using adaptors as shown right; just shove the hose adaptor in and it stays in place while pumping. It looks cheap but on a Gumotex at least works fine. Higher pressure boats like Grabners and Incepts and newer Gumotex have bayonet fittings (right); push in the inflation hose adaptor and turn like a light bulb so it won’t pop off as pressure builds. These bayonet type valves can still take an regular push fit hose-end, but it may pop off unless held down.

Pressure release valves
I’ve learned to be careful not let an IK get too hot, especially out of the water. On a warm day you can feel the side tubes tighten like a drum. This of course happens to be good for paddling efficiency but isn’t good for the seams or an I-beam floor.
mod-esc valveThe floor tube on my Sunny had a pressure release valve (far left black disc, left); oddly it’s something never mentioned in the specs. It’s there to protect the I-beam floor which could separate under pressure (I-beam floor explained here). The valve is set at a certain pressure to purge when the air inside gets hot and expands. It means an IK can feel a bit soft in the cool morning following a hot day; don’t worry, it’s unlikely you have a leak. The handy thing with the PRV is that it makes a good guide to how hard you ought to pump up the rest of the boat without a pressure gauge. At whatever pump effort the valve starts airing off, that’s the same or a-bit-more pressure to put in the side tubes which may not have PRVs.
lefielda6The air in an IK can also get cooled, for example when pumping up on a hot day and then putting in a cool river. Because you want the boat to be as rigid as possible, after inflation it’s worth topping up once the boat has got wet; splashing helps cool the sides. Topping up – or tempering – optimises rigidity and with something like a Sunny or Solar 410C you need all you can get. In the same way, pumping up your boat in way sub-freezing temps and then putting it on water which actually ‘heat’ it up, though this is a less likely scenario.
prvk40prvtestThe higher pressure Incept K40 had PRVs on all chambers which meant you could confidently leave it in the baking sun and it would safely purge and then feel a bit soft once cooled down back in the water. Picture left – Incept PRV test with the protective cap removed and purging correctly through the centre. Right, a PRV being resealed after leaking from the edges – shown below. This was because I failed to check their tightness after buying the boat, as recommended by the manufacturer. My Gumotexes never needed such tightening in many years ownership. I ended up fitting side chamber PRVs to my Gumotex Seawave to run higher pressures but protect it fully.


K40 PRV leaking from the sides not through the valve. Needs tightening with special tool.

grabnerprvOddly, my Grabner didn’t feature PRVs at all, even though it runs potentially damaging high pressures. One presumes Grabner are confident enough in their vulcanised construction to think they’re not needed. I do notice that Grabner offer PRVs to fit on the end of an inflation hose (right) which purge at 0.3 bar and so dispense with the need for a pressure gauge to check how much you’ve put in.

IK Pumps

bravohoseThe cheap and cheerful Bravo foot pump initially looks a bit crap, but I’ve found lasts well. Occasionally the yellow tube splits near either end if packed too tightly or left screwed in (right), so it needs cutting down and gets shorter and shorter over the years. Also, after many years a crease in the back of the bellows wears through, though it’s also easily fixed with duct tape. It’s a shame the Bravo pump is a tight squeeze into the Gumotex drybag’s outer pocket; with some rough treatment the pocket rips off the bag’s body. If you use a Bravo footpump very frequently it just plain wears out, so if you’re not travelling with it and using the car, an stirrup pump may be better.


barrel or stirrup pump isn’t something you’d want to tour with and is designed for pumping up full size rafts or lots of IKs. Pumping air on both strokes, it can achieve a much higher pressure more quickly, but works best on flat, firm ground where you can stand on the stirrup plates and get stuck in. The Bravo 4 item above was only about £20  but pumps up an IK in about 5 minutes. Later, I received a Bravo 6 with my Seawave but found this harder work – who knows why. The cheaper Bravo 4 does claim to be an ‘R.E.D’ sw05(reduced effort device) and I can confirm that this isn’t some gimmicky acronym – it is less effort even if (or because) it pumps on both strokes. Perhaps the fact that it’s designed for kites (paragliders – very high volume) has something to do with it. Only £15 in the UK.
Like the Bravo foot pump, the other port on the Bravo 4’s pump handle can be used to suck air out of the kayak so it rolls up good and flat. The strong spring in the foot pump works well enough to do this too; you can see creases forming in the hull as you suck all the air out.

pump-kpumpThe K-Pump Mini (right) is a top-up pump or a compact, 600-g travel pump. It takes 15 minutes to pump up my Seawave out of the bag with this, but the nozzle works on any IK. Fuller review of the K-Pump Mini here.
Until I got the Grabner which has no PRVs but runs a high, 0.3 bar (4.3 psi), I never bothered with a pressure gauge (manometer) and just pumped up by feel or until a PRV hissed. Now I am careful to make sure the Grabner runs at 0.3 bar, or a little over on chilly days. Since then I got a Gumotex Seawave and fitted PRVs to the side chambers. That means I don’t need to use a pressure gauge – I simply keep pumping until each PRV hisses.

This entry was posted in Gear, Gumotex IKs, Incept K40, Inflatable Kayaks, Sunny IK, Tech and tagged , , , , , , , , , , , , , , , . Bookmark the permalink.

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