At some point you need to drain the loop. How do you do it?
 
Do you just disconnect and quickly move over a bowl?
Do you have a plug at a low point specifically for draining?
 
I've only built one loop. When I did it I was advised to put a T at the low point so I could easily drain if I needed.
 
How do you do it?

I put in a drain plug at the bottom of my loop...the block and plug I used Koolance....their are others out their....I find it easier it to have a drain bottom with enough to get the drain plug outside of the case that way no water inside...just my .02.....in my mods pics the first pic you can see my drain plug and temp setup... 

Put a ball-valve with drainport drilled into the bottom of the case (from my build-log):

Interesting where did you obtain that ball valve? and more importantly do they carry 3 ways?

I have an inline drain valve (Koolance) below my GPUs right before the tubing goes back up to reservoir. To drain the loop I usually tilt my case, rest it against a desk and open the drain stretching the piece of tubing over a bowl/bucket. With sealed loop this drains only a little (vacuum lock effect).
 
Later I attach a piece of tubing to it and route it to bucket while I open the fill port on reservoir and open the drain on my external radiator. That drains most of water out, pretty much it leaves only pump and internal 360 rad with water in.
 
If I need to totally drain the system I disconnect the parts and drain them completely as I remove them.
 
Having a drain valve at bottom of loop rarely drains the whole system, all depends also on how the tubing is routed, how radiators are placed (horizontal/vertical), where the ports are, etc. etc.
 
Even with drain at bottom, my loop is a b*tch to drain unfortunately and having an external rad with bottom ports (that I used as extra drain ports) is a life saver. Draining the front 360 Crossflow radiator placed vertically is another story LOL, to that I usually remove it together with pump (connected to its "bottom" fitting) and drain those outside of case.

dipdippotatochip

Why must the loop be drained?

 
Just like how you gotta clean the dust out from a air system, you drain a loop to make sure the water stays fresh to keep algae and other build up.

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CAxVIPER

ak420boarder

Interesting where did you obtain that ball valve? and more importantly do they carry 3 ways?

I just picked mine up from performance PC. It is a bits power fitting, not sure if they make 3 way or not. 

 
Found them thanks. Though i'm really interested in a 3 way valve if anyone knows where those could be found.

There is always something a little more shiny! :)

flasher4q
I put in a drain plug at the bottom of my loop...the block and plug I used Koolance....their are others out their....I find it easier it to have a drain bottom with enough to get the drain plug outside of the case that way no water inside...just my .02.....in my mods pics the first pic you can see my drain plug and temp setup... 

Same here and with Koolance.
Bill
Also for the Drain Valve from Koolance is only $12.99
I order from Koolance's site for all Koolance`s products.

Using the 800D I have a single loop cooling the two 680's, the Vreg's and the CPU OC'd to 4.0... I drain this loop on the cheap... Everything is routing to the back for a very clean loop on the visual side...
 

 
 

 

 
 
Here is what it looked like on the other side when it was running a pair of 570's...
 

Very carefully

Personally, I always use a T of some sort at the lowest possible point of the loop, and a threaded plug in the end.  I also not have the shut off valve for it as well from BitsPower.  From the shutoff is a couple feet of tubing and the plug, so I open the side panel, hand the line out of the case into a container, remove the plug, and open the valve, let gravity do the rest.  Once it's drained, close the valve, then replug it and tuck the hose back inside.  No spills, messes or surprises.  If you don't have room for the extra tubing, with the valve like that, you can keep it separate on a barb and just thread it into the valve as needed, works just as well.