Should you depressurise compressor after use?

[lewis s]

After using a compressor is it ok to leave pressure in it to use another day? I still plan to drain it regularly and before spraying but for pumping up tyres and running tools it seems a pain to wait for it to pump up to pressure, use it for 5 minutes and drain it back down again.

Are there any implications with leaving it pressurised?

 

[cumbriasteve]

I often leave my small 25 litre tank full, the only thing I can think of is the air will have moisture in it, even with regular bleeding off, so it could speed up the internal rusting.

When I do bleed off after it's been sitting for a week or so, the run off is milky coloured and not as clean as a daily empty.

 

[rtbcomp]

I leave mine pressurised as I use it daily, but I do drain the moisture out of the tank and traps.

What I do sometimes is switch the pumps off just before I finish blasting and use the air in the tanks, down to about 40 psi.

Make sure the mains is off though so it doesn't start up in the early hours if you have a leak.

 

[brightspark]

After using a compressor is it ok to leave pressure in it to use another day? I still plan to drain it regularly and before spraying but for pumping up tyres and running tools it seems a pain to wait for it to pump up to pressure, use it for 5 minutes and drain it back down again.

Are there any implications with leaving it pressurised?

i allways leave mine pressurised. as long as u remember to turn it off as if u have a small air leak the comp will start up during the night which isnt good policy once air is in the tank the one way valve stops any back pressure being aplied to the pump valves

 

[pedrobedro]

In the instructions for mine it says to drain down daily or after use so that's what I do, leave it till the end of the day.

 

[rtbcomp]

My instructions say the same, but I take it to mean drain the water off.

 

[tigler]

Draining frequency depends on use, a compressor used everyday for some hours does need draining daily or the receiver will fill with water formed from condensate fairly quickly, this reduces the receiver volume so the compressor will need to run more to maintain pressure. Also of course, the water doesn't do the receiver much good.
Compressors used infrequently do not need draining every day, maybe once a month or even less is acceptable.

 

[FranV8]

You don't necessarily have to depressurise, but it would be worth opening the drain cock on the receiver after a day's use. For my tiny 25l compressor, it's no hassle to let it pump up again every time I need it, so I leave it with the drain cock open.

Often, workwise, I have involvement with recievers in the 100's of litres class - 24/7 operation, they almost exclusively have auto drains on them. They also have the benefit of being on a pressure systems register, so their internal condition is assessed annually by an independent inspector.

For your (assumed) home machine, that won't benefit from internal inspection, and will have mild steel internals, I'd make a point of at least opening the drain cock for a few seconds at the end of a work session, even if you close it up again and leave it pressurised, at least then you've minimised the moisture in there and therefore corrosion rates.

 

[Chipper]

I drain mine down, though as it's mainly for spraying, I figure the less water kicking around the better. It seems to blow a bit of water even when the pressure's fallen to say 10psi, notalot, but it does spit.

With the missus' 24 litre one I make sure she drains that down every time as it makes such wet air. There's usually more juice than from my 150 litre. Only takes a tic to fill anyway, as per ^.

 

[hunter27]

I don't know if this is relevant but with diving cylinders we were always told never to leave them empty to reduce condensation in them.
pete

 

[awemawson]

Mine is powered up 24/7 - I was scrupulous making sure all the pipework was leak free when I installed it,checked every joint with soap solution, and did a pressure test on each section of piping (It runs over three buildings), and to make sure I'm not loosing air I have a running hours meter on the compressor so I can check it's not running away with the 'leccy bill. If left unused it takes over a week to cycle. Means I have air when I need it and where I need it, with the compressor in a remote Portakabin so the noise isn't an issue spoiling thinking time!

 

[penfold]

I don't know if this is relevant but with diving cylinders we were always told never to leave them empty to reduce condensation in them.
pete

That's because HP air is normally supplied totally dry; compressor set ups at dive shops will have big refridgerated driers, which means cylinders will never have internal corrosion problems. portable HP compressors are a bit more problematic, and can pass moisture into your tank.

The OP's LP compressor will be fine left charged, just be sure to drain off moisture last thing before locking up the shed. On ships the systems are (supposed to be!)permanently charged, so draining moisture is done at every watch change(every 4 hrs).

 

[lewis s]

Thanks for the great replies! It is a home 50l compressor and from now on i think i will keep it charged and drain it down periodically. Its main use will be to pump up car tyres so will have only light use until my car working weekends where i will be using all of my other new air tools

I will also add that i did'nt realise what i was missing out on when i didn't have a compressor! I managed to change all 4 wheels on my car in 15 minutes yesterday, and the shears are great!

No doubt more questions will be coming soon

 

[dannyp]

mine are up to pressure 24/7

but the tanks are all slightly tilted so watre runs to the drain hole but ive removed the drain taps from the tanks and piped them all up together to a ball valve on a pippe that goes outside.

every now and again crack the valve open to let the water out. rember preping a car for paint on a foggy evening and we got gallon and gallons out the drain after a few hours

 

[rtbcomp]

The instructions with one of my regulators advise against leaving it under pressure when not in use. I have ball valves on the inlet side of my regs to isolate them.

This would be essential with autodraining ones which rely on being de-pressurised to open the drain cock.