Hello everyone, i have a question about draining the air brakes…when/in what weather conditions would you most likely need/feel the need to drain the air out to get rid of any liquid in the tanks/system?
i know this is a bit premature due to the fact that i need to pass my C test before i need this info, but would be very grateful for any advice on this. Many thanks
humid and wet weather would be the worst conditions for it.
A question for everybody though, How often does everyone drain theirs?
at least once amonth,and also check when your Filter for the AIR-DRYER WAS INSTALLED as it should be changed YEARLY or early if and when required,
It used to be every day when they were the butterfly type valves but since the introduction of Air Dryers the need has greatly reduced.
Even on the rare occasions that I have checked then, very little, if any, moisture has come out.
so how is it done and where is it situated. I wouldnot know anything about this question. any pictures
If you look under the air tanks you will see ring-pulls like key-rings. They may be connected with a wire give it a tug & air will escape from the valves__. Be careful you don`t pull the rings on the self-destruct modem. These are basically hand grenades & can cause problems !!__ 
goofball:
so how is it done and where is it situated. I wouldnot know anything about this question. any pictures
On the sides/ends of the air tanks usually next to the fuel tank or around the same position on the other side. Like Harry says, there’s a ring on the end of them usually. All you’ve got to do is press the valve in with your foot or whatever and you’ll hear the air rush out. As has also been said, it’s very VERY rare to get any water coming out of them on modern trucks.
On our Y plate Scania and 55 plate actros i’m yet to find a drain valve. 
maybe its done automatically on those…but i could be wrong.
try looking for a little metal pin sticking out from the bottom of the Air tank
this has to be pushed in if fitted., a pressure regulator valve will also be fitted
this is to allow air to escape when the pressure is too high , also a good
check point to see if the compresor is working alright and not takeing oil into the system,as it will show in the air escape point on this valve.
If you cant find the valve try going up a lumpy track up to a farm and you will generally find out that way as you lose all your air as you knock the valve off and end up immobile in a heap of cow [zb]
ERF’s are famous for it as I can personally vouch
Well there must be about 8 air recievers under each of them and with out actually getting on my back underneath it i havent been able to see valves. None else there knows where they are either. 
have a look here it is quite good
-http://images.google.de/imgres?imgurl=http://www.ndt.co.th/pictures/spec_tracter_img_1.jpg&imgrefurl=http://www.nissandiesel.co.th/model_desc.php%3Fid%3Ddvnekmqtdxwjmzdpezym&h=290&w=148&sz=11&hl=de&start=20&tbnid=K-cmU2_Pz32uBM:&tbnh=115&tbnw=59&prev=/images%3Fq%3D%2Bair%2Bbrake%2Bsystem%2Bfor%2Ba%2Btruck%26svnum%3D10%26hl%3Dde%26lr%3D%26sa%3DG
might help you out ,
