Inflatable packboat valves, PRVs and pumps

Updated June 2018

IKvalvesThe best inflation valves for an inflatable packboat aren’t the simple bungs you find on an airbed or an old Semperit. Nor the twist valves off a Feathercraft Java or an old Alpacka.
What you want are one-way valves like the high-presure ones off on white water rafts, pictured left and copied by many. Like a car-tyre valve, one-way operation as well as a secure fitting are the key, so what pumps in doesn’t push back at your or escape when you remove the inflation hose.
pump-barrelgrabvalveWith proper raft as found on good IKs valves, pushing the button down and turning clockwise locks the valve open to release air. Then, for pumping up, push lightly and turn anticlockwise so it springs gumvalvesback 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.
Old Gumotex valves were cruder versions of a Halkey Roberts; post-2010 Gumotex valves gumvalveuse superior ‘push-push’ valves (right) which lock open or close by simply pressing, like a click biro.
valvespannerI always make sure I refit the cap seal straight away to keep grit or water out.
I’ve found these types of valves to be reliable on all my IKs although this grabtoolGumotex 410C owner didn’t. 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; see below) should it play up.

pump-bayopush-fitadapterWhen it comes to inserting the inflation hose, one-way IK valves can take simple push-fit adaptors as shown left; just shove the adaptor in and it sort of stays in place while pumping. It looks cheap but on a Gumotex at least, works fine.
With high-pressure boats like Grabners and Incepts and some Gumotex, you’re better off using a hose adaptor suited to bayonet fittings (right) so the hose won’t pop off as pressure builds.

Low-pressure valves for packrafts
anfi - 13Screw-cap Boston valves  are used on cheaper IKs as well as slackrafts and packrafts. They have two bosvalvcaps: the main one unscrewed (left) to dump the air, and a square cap to access the one-way valve to top off a boat (right).
valve-bostonThese are low-pressure valves using a simple soft rubber ‘mushroom’ on a stem (right) which is fine on a boat you top off by mouth, not a pump – ie: packrafts but not proper IKs. With a packraft, the one-way valve eliminates the need for a separate oral top-up valve which means one less thing to leak or malfunction.

Pressure release valves (PRV) for IKs
I’ve learned to be careful not let an IK get too hot 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. Nifty.

bravohoseIK Pumps
The cheap and popular Bravo foot pump initially looks a bit crap, but I found lasted well and was fairly travel-compact. Occasionally the yellow tube split near either end if packed too tightly or left screwed in (left), so it neededcutting down and got shorter and shorter over the years. Also, after many years a crease in the back of the bellows wore 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. If you use a Bravo footpump very frequently it just plain wears out, so if you’re using the car to get to the water, a stirrup or barrel pump is 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 Kite pump above was only about £20 but pumps up an IK in 5 minutes.
Later, I received a Bravo 6 with my Seawave but found it hard 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. Pumping up is effortless and they cost under £20 in the UK, last time I looked.
Like the Bravo foot pump, the other port on the Bravos’ pump handle can be used to suck air out of the kayak so it rolls up good and flat; you can see creases forming in the hull as you suck away.
I left my Bravo 4 at home one time so bought a Sevylor RB2500G barrel pump for only a tenner posted off ebay. Same size as the Bravo barrels, it looks as well made and worked well for the awkward sevypumptopping-up of my Semperit’s lilo plugs. It cames with push-fit, lilo-plug and bayonet adaptors and will suck as well as pump. But pumping up my Seawave from flat was exhausting due to friction or the effort towards the end; I actually got out of breath and had to rest. Morale of this fascinating story: get a Bravo 4 Kite pump and the right adaptor for your boat.

pump-kpumpThe K-Pump Mini (left) is a handy top-up pump or compact 600-g travel pump. It takes 15 minutes to pump up my Seawave; the push-fit nozzle works on any IK with one-way valves. You have to press the body of the pump against the valve. Using it a lot one time, I got the feeling it might break something or wear out the seal (which needs regreasing once in a while). Fuller review of the K-Pump Mini here.

Pressure gauge
amigaugeUntil I got the Grabner which has no PRVs but ran a high, 0.3 bar (4.3 psi), I never bothered with a pressure gauge (manometer, left) and just pumped up by feel. Since then I got a Gumotex Seawave and fitted PRVs to all chambers. That means I don’t need a pressure gauge to get the right pressure – I simply keep pumping until each PRV hisses: the boat is then at operating pressure. Very handy.

This entry was posted in Cheap PVC 'slackrafts', Gear, Gumotex IKs, Gumotex Seawave, Inflatable Kayaks, Tech and tagged , , , , , , , , , , , , , , , , , , . Bookmark the permalink.

One Response to Inflatable packboat valves, PRVs and pumps

  1. Simon Harvey says:

    great article – thanks

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