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I'm planning to use a pressure washer for the first time, as a "once off" task, to clean and remove caked-on and ground-in mud, dirt and debris from rebar and concrete beams, before I pour concrete to embed them.

The pour was delayed for over a year, during which time everything was heavily soaked, walked on, ground in, and baked on, during that time, so I need to strip back to the materials themselves before pouring.

I'm aware of the seriousness of injuries that pressure washers can cause. I'm likely to be using an electric-powered washer at the higher end of domestic pressure, in the region of 130 bar/2000 psi operating - not "maximum" - pressure. I've got steel toe leather boots, leather welding gauntlets, and a cheap full-face plastic visor possibly with goggles too, lined up. I can't think of anything specific I could use for leg, torso and arm protection.

I'll be working mainly in a long 1.2m x 70cm trench, and spraying the beams and steels from below and at the ends of the beams. The beams stick 20-25cm into the trench from one side. That means it will involve close-range work, at upward and other odd angles, with no scope for a long lance and even "full arms-length" won't be practical for much of it. On a positive note, being in a trench also means there's less scope to trip or fall over, and recoil force should be ok since I'll be almost always be within inches of a rigid vertical backstop behind me.

Obviously I'll be pointing it away from me (!) and aiming for avoidance in the first place, but if I'm accidentally caught directly by the spray, by flying debris, or by water spray "bouncing" off the target, will these be adequate, and what else might be appropriate?

Also on a similar note, is the spray bouncing back off the target still capable of causing serious injury, or has it lost enough force on impact to no longer do so?

Comment: I'm not looking for answers that just say "most people don't do that much, so it's fine" (I know that most people don't do this much). I've had serious injuries and am quite motivated to avoid another. I'm more looking for reasoned comment on the proposed safety measures, the risks, and the scope/reasonableness of anything else that could be worthwhile. Thanks :)

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    I'd consider swapping the leather boots out for something waterproof. Unless you've got exceptional drainage the runoff is going to pool in the bottom of the trench, and standing with wet feet for that long is beyond unpleasant. You'll definitely want the face shield and a raincoat too, as hitting the dirt walls will fling mud everywhere. – Matthew Gauthier Sep 27 '18 at 11:40
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    The biggest safety device here is your brain. Keep your mind on your task and you'd be hard-pressed to hurt yourself. The stream is only immediately harmful out to about 12 inches. Frankly, driving around in a car is more dangerous. – isherwood Sep 27 '18 at 13:13
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Unless you are unusually clumsy, the extraordinary protective devices you've listed would be excessive.

Eye protection in the form of safety goggles or safety glasses would be appropriate. If the debris you are blasting is at or above eye level, your clear plastic shield provides sufficient protection for your entire face. An ordinary ball cap for head protection takes care of the top.

If you don't care about being soaked by the water, long sleeve shirt with a button up collar and suitable long pants and boots will protect the rest of your body. Hand protection by gloves of almost any type (other than latex or nitrile) will do the job well.

If you wish to avoid being soaked by the spray, there are inexpensive Tyvek brand full body coveralls, equipped with hoods that will shed water. I've used them to operate a weed eater and avoid the "back-spray" of vegetative matter from the cutter. It would be well suited for use with a pressure washer in the environment you describe. All that would be needed beyond the coveralls is a pair of gloves, as the suits include built-in booties.

The bounced spray has very little power. I've been struck in the face with bounced spray and it has approximately the force of a strong rain. You may already be aware that the direct force of the spray can cut skin. I can confirm that.

I suspect the biggest danger to which you will be exposed is debris and gravity. If the debris is small and the distance is short, neither item should be much of a factor. The air space under a Tyvek coverall and the fabric will absorb much of that energy.

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    The biggest danger, in terms of potential injury, is going to be the trench collapsing. Even if it's unlikely, having someone topside would be prudent. – Matthew Gauthier Sep 27 '18 at 11:35
  • Trench is braced 20 ways to hell, already :) but a good point. – Stilez Sep 27 '18 at 18:57
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I think the worst that you can encounter is contacting your skin with the stream or getting debris in your eyes. I have hit my leg before (when I was young) with the stream and it does tear the skin and hurt, but Iived to tell the story. You'll find that pressure washing in goggles or glasses is difficult, they get quickly covered in spray and dirt.

As you mentioned, I take none of these precautions. I only take it seriously when I'm pressure washing on a ladder or anywhere else I can fall. On larger washers, the kick after pulling the trigger is no joke.

  • The stream can definitely break the skin, and worse, can force dirt and germs into the cut. – stannius Sep 27 '18 at 17:15
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I believe a rain suit and face shield should be enough, I regularly pressure wash my big tractor and have never been injured by the blow back from a 5000 psi 3gpm industrial pressure washer, if you will be working in the trench a pair of rubber boots may make help, I use rubber boots in the winter and even with my gernade tip the rubber will be enough protection as I rinse my boots off with the washer about a foot (pardon the pun) away with no damage to the boots.

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