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Just got a new compressor and I wondering if I should be releasing all of the pressure out of the unit when it is not in use? Or is it better to leave the pressure in so that the unit does not have to work as hard to build up the pressure next time?

I am not planning on using the unit daily. Mostly for weekend projects and regular maintenance (airing up car tires... etc).

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  • SCUBA tanks are stored at between 25 and 300 psi (consider they normally hold 3000 psi), specifically to prevent moisture from entering the tank. Does the same theory not hold true for these tanks as well? There is a major difference in the air though: that air that goes into SCUBA tanks goes through a moisture separator and filters to make it moisture- (and oil-) free.
    – gregmac
    Jan 27, 2012 at 16:29
  • The instructions say to drain, not decompress. I have mine pressurized all the time and drain the tank about once a month.
    – Gil
    Jan 29, 2023 at 19:33

7 Answers 7

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The instruction manual for my Sears Craftsman 3 gal., 1 hp, Horizontal Tank states to drain the tank after each use or daily and also for storage. The water that may be in the tank could corrode and damage the tank.

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  • It may depend on the tank size. I've got a 1 gallon DeWalt, and it says the same thing. What about something like a 60 gallon compressor though? That's going to take a lot more work to re-pressurize than a few gallon compressor.
    – Doresoom
    Dec 2, 2010 at 17:34
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    Larger compressors (and even many smaller ones) will have a water drain at the bottom of the tank that can be used to get the water out. Open it until air comes out instead of water, and you can then close it leaving most of the pressure still in the tank.
    – Mike Powell
    Dec 2, 2010 at 17:53
  • @Mike: That makes sense. I was thinking small picture - if I open the valve on my one gallon tank, it's empty in a few seconds.
    – Doresoom
    Dec 2, 2010 at 21:34
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Yes, definitely drain it after each use. Need to avoid letting water pool in the tank, possibly corroding and weakening it. Release the air and open the drain valve for a while to let out any condensation.

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I always drain my compressor when finished, mainly to blow out any moisture that could have built up inside. You should vent the air through the valve on the tank itself (facing towards the ground) for at least the last 40-60 lbs of air to help blast out and remaining moisture. I also always leave the tank valve open and facing down to help keep it dry inside.

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    Vent it with the valve facing towards the ground. On the compressor I've used before, the vent was up the side a little bit. If you just opened the valve, there would still be a pool of water in the bottom.
    – tehDorf
    Jun 19, 2015 at 21:48
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If you open drain valves too quickly moisture that settles to the bottom of the tank gets dispersed. Crack valves SLOWLY till water starts to drip to allow water accumulated at the bottom of the tank to drip out. That is all you need to do on a daily basis. If it makes you feel better you can drain tanks completely every couple of weeks. The only reason I can see to relieve all pressure is to relieve high pressure from the regulator in order to protect seals. I make a habit of draining pressure down to 50 lbs daily for this purpose.

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While draining the water out of your compressor is a good thing, draining all of the air out daily is not. When you compress air, it's ability to hold the moisture already in it, decreases, causing condensation. So you are actually defeating the purpose. And you prematurely wear out your compressor by running it so much.

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Release the pressure. If you are carrying a pressurized canister and you, say, drop it on a concrete floor, it could fracture, sending shrapnel everywhere. In other words, a pressurized canister is a bit like a small bomb.

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  • Most (portable) compressors that I've seen have wheels so they can be rolled around. I've seen portable air tanks (designed to be filled, then taken to where the air is needed) with just a carry handle, but they don't have a compressor attached. How many actual compressors have you seen that are designed to be carried and not rolled?
    – FreeMan
    Apr 28, 2021 at 14:59
  • Fortunately there are design regulations and to be sold in the USA they have to withstand obvious scenarios like that.
    – whatsisname
    Jan 29, 2023 at 21:01
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My 3 gal [ the Sausage Shape and not the Pancake one ] was not that old , and it would not stop running as it was not building up the set pressure on my regulator to shut off. When I shut it off it sounded like I was being attacked by a herd of mean spirited snakes !! So much hissing as that 300 lb rated hose had more holes than a 10 lb piece of swiss cheese !!

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    Yikes! Please don't shout at us, it's totally unnecessary for you to be heard. If you'll take a moment to take the tour, you'll see that this is a Question & Answer board, not a general discussion forum. We like answers that are based in fact (granted, most of the answers on this question are "I've always"...). Also, you're addressing an issue that could be simply resolved by disconnecting the hose from the compressor and not draining the tank, so you're really answering a different question. Additionally, I've had the same air hose connected to my compressor [con't]
    – FreeMan
    Apr 28, 2021 at 14:46
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    (2 different compressors, actually), for at least 15 years and the hose itself hasn't developed a single air leak, so the issue may have been with your particular hose. Unfortunately, unless to edit your post to be more of an answer and less of a rant, it will be quickly deleted, as this isn't really appropriate at this site and we do police it fairly rigorously.
    – FreeMan
    Apr 28, 2021 at 14:48

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