Unfortunately you havent heard from the thousands (likely worldwide) that have had 0 issues with an EK Block on either a 3090 or 3080.
 
That Corsair 1000D is "screaming" for a large custom loop (like my old 900D), so many options for Rad placement, great case choice!!!

I believe the issue comes from when people uninstall the factory heatsink.
Wether it's people ripping off components while disassembling or insufficient solder joints on EVGAs end I couldn't say.
 
I will say I successfully installed an EK block on my 3090ftw3 ultra.

the_Scarlet_one
I have two 3090’s on water using EK Quantum blocks. I haven’t experienced the issues that others have, so I am not sure what could be causing the issues others have experienced. I have only ever used EKWB products for my GPU’s, so I trust them personally, but there are other options available if you decide that you don’t want to risk your cards.

Hello what do you mean whit other options? Undervolting or so?

What about the thermal Pads Came whit the Waterblock? Some Users mean these are to thin and some vram und VRM does not have contact whit the Block and they used other thermal Pads

Subzero30k
Hello i had this card since Christmas and i love this beast

But for me its to loud and Hot the card reaches 78° degress

I have the card installed on a corsair obsidian 1000D case whit max fans installed

I bought everything to Build a costum loop.

I selected a ek Quantum waterblock for the card

Now i heared many 3090 and even 3080s died after installing the Block

Now i dont know what to do? I have two of these 3090 cards

Should i try the Block or maybe buy a other waterblock?

Installed the EK Waterblock (Nickel/Acetal) yesterday 
 
First of all: Yes I was concerned too due to the forum posts here... 
 
What I figured out:
 
The old thermal paste is sticky as hell. Due to that I ran some stress tests (3D Mark) to bring the card on temp. After that I took out the graphic card and started with the dismantling. The backplate was easy to dismantle (and yes you also have to remove the GPU bracket! - the manual from EKWB is not so informative but you should take a look at the manual of EVGA regarding the hybrid AIO manual; Important: the GPU bracket is under heavy pressure, hold it a little bit down during the removal - dont use too much pressure!). The cooler itself was a little bit more tricky. At the end you should take your time and dont try to dismantle it from the end on (easy to bend the board in total). I was able to remove the cooler from the side (upper end - not the PCI-E side). 
 
After the old cooler was removed it was time to remove the old thermal pads and paste. The pads are no problem. The sticky paste at the VRM took more time. At the end no problem at all. During the installation of the cooler I only had a problem with one screw (the screw seems not to fit the screw thread - result: I omit the screw (was not essential)). Always use the plastic washers!
 
After that the backplate was next. Its important to follow the install manual from EKWB regarding the thermal pads especially for the 3090 (correct thickness at the right place - you have 1 mm, 1,5 mm and 2 mm). After installed the thermal pads exactly as described I figured out that the RAM pads are not correctly covered. Due to that I extended the pad on the backplate a little bit. After that comes the most important part: Mounting of the backplate screws. Dont tighten the screws too much. Just tighten them until you recognize a small resistance. 
 
Until now no problems with the card.  
 
 
 
 

I just recently got my 3090 ftw3 ultra on water with EK's block. I just posted a thread in here showing it off. I'm new here or I'd post the link. 0 issues with the process and all is well. Just took my time and kept grounded with a grounding pad the entire time (better safe then sorry). Happy I did, quiet and cool as can be.  

Hello i had a question i Start my work in two days

I checked the Manual for the EKWB Block

On the gpu is a small evga Logo on the back off the card

Do i have to remove this or can it stay?

GTXJackBauer
Test out the GPUs on air and once everything is operational, put the blocks on.  

That's one monster case.  I look at my 900D with disgust because of it's size/weight.  Has grown away from me but it's great in the beginning so soak all the fun.  I might be looking to go light the next go around.

GL and post some PC pics here once you're up and running.

I feel exactly the same about my 900D....but....there is so much space in there when working on loop for my big hands...hard to give it up!!!!