A lot of your questions have already been answered but some weren't, and there were a few answers that I disagree with, so I went a little overboard here
Originally Posted by Ukkooh Rads
I know that the rads should be flushed properly before using them but is it ok to do it with tap water? Is it correct that you don't have to clean them with vinegar or such due to a new solder type? I read some fags in ek's website and according to them vinegar hurts the nickel plating so I'd be scared of some of it staying in my rads if I used it to clean them.
Also are these still the best performing rads for this thickness?
A lot of people flush with tap water but do a final rinse with distilled. The reason is that common tap water contains greater amounts of minerals and bacteria etc., and you want to keep those contaminants out of your loop to the greatest practical extent because you want to minimize oxidation/corrosion and biological growth in your loop. Distilled water is very pure, and usually quite inexpensive and easy to obtain. In the US at least, you can get it at supermarkets for $1 or $2. Check your local grocery or hardware stores.
About using melted snow: IMO not a good idea at all, unless you live in a very clean rural area without any cities within a thousand miles upwind, or you're getting it from inside a thousand-year-old glacier. Otherwise, it's not going to be better than distilled water, and assuming your city has modern water treatment facilities, tap water will likely be cleaner as well.
Vinegar is an acid, so it will damage things if it's too concentrated or left in contact for too long, but it's safe to use it for brief periods. You should be extra careful using it on plated blocks or fittings since the plating is a very thin layer that is much more fragile and will show damage a lot sooner. Nickel can be discolored quickly by vinegar even without physical damage. But there's no nickel inside a rad, so as long as you flush things out afterwards, you'll be fine.
The alphacool nexxos rads are very highly regarded so that's a good choice
Is the size purely an aesthetics thing? Is bigger tubing much harder to install than smaller? Is, for example, 13/10 tubing more or less likely to leak than 16/10?
I'm currently trying to decide between 13/10mm, 16/10mm and 19/13mm tubing and I'd love to get some suggestions on this. I have no idea how many meters of tubing I'd need for my planned loop so it would be great if you could give me an estimation on that.
It's partially aesthetics and partially practical, pretty much like everything in watercooling
Most people seem to prefer the larger tubing since that will also allow for better water flow. When properly installed, it won't leak no matter what size tubing you use.
Three meters of tubing will give you enough, with some to spare if you make a mistake.
From what I've heard you should never use any colored coolants. Is the ek clear coolant good or will it stain my loop? I've heard that distilled water with a biocide is the best coolant but I have no idea where I could buy distilled water. I hope someone else from Finland could give me a tip on this.
I personally use distilled + biocide because it works and it's very inexpensive, but there are some perfectly good premixed coolants out there. Most warnings about using dyes or premixed colored coolants have been because some of them can break down over time and leave gunk that can clog your blocks. However, I don't read as many complaints about that as there used to be, so my assumption is that the newer products do a better job in that regard. I haven't seen any complaints about the EK coolants causing problems, but since I don't use premixes, I haven't really researched it too deeply. Anyway, I think it's safe to assume that a clear coolant won't stain anything since it is colorless
Do I also have to flush or clean the blocks before using them? Are the gaskets reusable or do I have to replace the blocks every time I open them?
I would recommend flushing out radiators, but it's optional for blocks. It won't hurt anything if you do. The O-rings are reusable and should last a long time; however it's a good idea to inspect them when you do open things up to make sure they are undamaged.
Is it safe to move a pc with a loop without draining it? I carry my rig to lan parties pretty often and this has been worrying me for a while. Mostly I'm worried about the res leaking. How tight is the lid on those?
It's safe to move it without draining if you are careful. All that copper and water makes things quite heavy though, so keep it lying with the motherboard flat and face up to reduce movement on the graphics card.
Also, there shouldn't ever be any open ports in your loop anywhere so there wouldn't be any leaking. A port is a port is a port whether it's on a block, res, radiator, or pump, and they should all be sealed with water-tight fittings or stoppers.
Good luck with your build and keep us posted on how it goes!