When drilling new holes for expansion anchor bolts, you need to clean the dust out of the hole before you hammer in the bolt. People will accomplish this by either using a blow tube or a bellows and a wire brush.

I've been wondering about how effective using water to clean out a bolt hole would be. If you were to blow water into the hole after you blow the dust out to wash it thoroughly vs brushing it. I know many 3/8" expansion bolts are rated for under water use, is using water to clean out your hole effective?

  • 3
    I assume you are referring to segment anchors (vs glue-in). That's maybe worth mentioning explicitly, as it definitely makes a difference.
    – imsodin
    Commented Jun 5, 2017 at 8:57
  • @imsodin Correct, I'm referring to expansion bolts.
    – ShemSeger
    Commented Jun 6, 2017 at 3:42
  • I don't know much about climbing, but I assume you are drilling with some kind of power tool in granite or a similar stone. How are you keeping the drill bit cool? Commented Jun 6, 2017 at 17:24
  • 1
    @JamesJenkins I'm drilling mostly in limestone and dolomite, and I'm only drilling one hole at a time, so the bit doesn't get a chance to get real hot.
    – ShemSeger
    Commented Jun 6, 2017 at 17:30

1 Answer 1


Disclaimer: This answer reflects nothing else than my own opinion on this subject, since I've never used water to clean holes nor know anyone that does so.

So, first thing I'd like to ask you is: why? You'd have to carry more weight, and there's absolutely nothing wrong with cleaning the holes using air. In fact, as far as I know, industrial bolting manuals do recommend that.

Now, assuming you have a good answer for the "why?" part, let's think a little bit. What happens when you inject water in a bolt hole (careful when pronouncing those words)? Well, firstly, it fills with water. This is per se a problem, since the whole was already filled with rock powder, which is very thin, and after getting moisturised it will turn into a thick rock porridge. Good luck removing that from the hole.

Afterwards, what happens? You find a way to place the parabolt inside, and then you start to torque it. But the parabolt already crushed a significant portion of rock porridge, which entered the casing. This will probably make it harder for the casing to grip the rock and will fill it to some extent with moisture. As one might think, rock has also a pH level. Moisturising acidic rock will make its powder more efficient in corroding metal (and don't fool yourself - stainless also gets corroded). In a word: this doesn't look good.

Let's think and try to make it look good. One thing one must consider is the angle at which the water straw is placed inside the hole. If directly or carelessly placed, turbulence effects will guarantee that rock powder accumulates in the end of the hole. What I wrote above is the result of this process.

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Now let's think it's somehow possible to fill a hole with water from a fixed position, very close to the wall. This would diminish greatly the turbulence effects due to water evading the end of the hole.

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But let's be honest: that's impossible. Conquering a route is stressful enough to think a climber would be able to place a water straw in a fixed position. The dust would eventually get moisturised.

The only missing situation is where the climber removes the dust with air first, then injects water in for some "I have no idea" reason. This is safer, since the powder would be already out, but I'm pretty sure it would make locking the bolt casing harder, since it would reduce the friction between the casing and the rock. It also looks incredibly pointless, since the dust would be already out and the water would activate the rock's chemical properties much more efficiently - and that's some efficiency you don't want.

Conclusion: I don't think you should do that. Follow the bolting manuals and use air. It's perfectly safe, you don't have to carry it, and it has never failed before.

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