I recently bought an air compressor for airbrushing and other uses. I'm not familiar with air compressors so I was wondering if it was normal for the air tank to have sand/gravel inside it? When I tip it over from side to side, I can hear something like sand/gravel moving around inside. The manual doesn't say anything about it.

  • 1
    None of the compressors I've used has had this. When you open up the drain valve on the bottom, is the condensation that drips clear, or does it have a lot of rust?
    – BMitch
    Oct 3 '11 at 2:09
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    I bought it new and I don't see any rusting. I've never used one before and there's all these warnings about combustion with rusting inside the tank, etc. I'm just worried that there'd be problems in using it. If this isn't normal behaviour, I'll just go and exchange it for another one. There's quite a bit inside, sounds like there's half a mug of sand.
    – Jack
    Oct 3 '11 at 4:33
  • For a new one, I'd definitely exchange it.
    – BMitch
    Oct 3 '11 at 11:06
  • NOT NORMAL! usually means something inside the pistons are giving way and disintegrations and pieces of metal are now inside the tank or somebody somehow put something in there bypassing the filter or messing with the piston system.. Maybe that's why you got a bargain..It needs inspecting or you might have a serious problem later.
    – Piotr Kula
    Oct 3 '11 at 11:11

No, there should be nothing loose inside there by design. If it is a used compressor, then I'd expect it is some rust that has broken loose. If it is new, then it is probably a piece of scale from when the tank was welded, or some other junk that got left in the tank. If it was a cheap compressor, then you got what you paid for.

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    It's a new compressor $100 that was on sale for $50. If there's not supposed to be something in there, then I'll exchange it for another one. I'm just worried if there'd be any problems using it.
    – Jack
    Oct 3 '11 at 4:27
  • I don't think it is a problem, unless there is so much stuff in there that it impacts the amount of air that can be stored. If you move it around, can you feel significant mass shifting, or is it just noise? The only other reason why it might be an issue is that if the "stuff" in there is steel crap, it will tend to rust and possibly cause future problems.
    – user558
    Oct 3 '11 at 13:41

I recently bought an silent air compressor similar with California Air Tools 5510SE. I have the exact issue like you and found out that are some very small steel balls probably resulted from the welding process. I intend to remove the tank plug and purge it.

  • Welcome to Home Improvement! Thanks for the answer; keep 'em coming! Apr 26 '19 at 14:41

I encountered the same thing on my recently bought air compressor. I decided to shake them out while changing the drain plug with a ball valve (I always do this before first use, because drain plugs have a tendency to clog up).

I removed the drain plug and poured some out, they looked like weld spatter so I figured they must be left over from the welding process. Only later I realized it was not weld spatter (because there was just too much of it to be spatter) but it was the granular flux used in submerged arc welding.

I decided to keep them inside the tank because this granular flux actually contains sacrificial metal particles, which oxidize before the base metal. This effectively prevents (or at least delays) the rusting of base metal.

If you have to keep the drain plug for some reason, consider shaking the particles out because of the increased clog up risk, but it is much easier to change the plug with a ball valve.

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