FLUIDXP Where to buy?

are you still under your service warranty?  if so, i'd recommend contacting DS directly to at least get tech support to walk you thru the process. 

you can contact the coolant manufacturer here: http://fluidxp.com/main/

if you really want to stay with their product.  or once you flush out the remaining coolant you can go with another brand. 

inspect your rig for a leak with that much coolant missing from the loop.  look for stains around the base of the inside of the case and around all tube connections, rads, fittings and blocks.  if you have a leak you might need to replace o-rings in the fittings.  you probably need to replace the tubing by now if it's soft tubing.  disconnect the psu prior to working on the LC loop.  and don't run the pump w/o fluid in the loop.  for refilling and leak testing make sure you disconnect the power supply from the rest of the system and only have the pump plugged into it (or use an entirely separate psu to test and fill the loop). 

could've been evaporation or a leak that's why.  i don't have your pc in front of me, so i wouldn't know.  just wanted to help you out.  mine was down to half and i had slow leak.  so take it fwiw.  sometimes with the Aventums it's hard to look in every little space (like the basement where 2 rads block your view w/o taking it apart).  after 4 years it might be a good time to tear it down and replace discolored tubing, check for gunk in the blocks/rads/fittings, and do a thorough flush at the least.  but it's up to you how little or how much you want to do.  good luck with it.

Thanks for the response.

No I dont have any leaks. It is a natural process of evaporation due to micro pores in the tubes so its normal when the coolant level in reservoir very slowly changes in so many years. I have been keeping my eyes on it.

As I mentioned in my first post, DS booklet says FluidXP.

I have decided to go with EK EKoolant EVO Clear or the EK-CryoFuel Clear Concentrate coolant. I will be flushing out the loop with distilled water. I didn't realized that FluidXP is a really expensive coolant.

Now I just need to figure out how to drain the loop. Aventum II is a big system with 3 radiators...Im not sure those quick disconnect fittings is going to benefit me to drain the coolant unless I get identical fitting to reconnect it back in order to drain the coolant. It is Koolance black colored brand fittings. I searched online for it but it seems they stopped making them as Im not able to find it. Its the kind where you pull the outer ring back to disconnect as its labeled on the fitting (not the kind where you push the two fittings inward and twist it off to disconnect). There are two Koolance fittings at the graphic card blocks (input and output) and another 2 directly at the cpu block.

I heard that using vinegar in coolant loop is a big no. Even EK website says using vinegar is NOT recommended.

How do I power the pump without powering the rest of the system?

Edited by Blackstar - 15 Aug 2017 at 12:35pm

you can unplug everything from the psu except for the pump (just trace back the wire from the pump to psu).  or you can use a separate psu to do it.  

If you have LC you should always check for leaks, if there is liquid there can be leaks so checking for leaks should be a part of regular maintenance of a lc system. Also one should flush their system once a year for best performance and maintenance.

QDs as mentioned make this very easy.