# Is fan efficiency affected if it not pushing, but pulling the air through a liquid-cooling radiator?

## All we need is an easy explanation of the problem, so here it is.

TL;DR: if I mount high-pressure PC fans on a water-cooling radiator so that they will not be pushing the air into the radiator, but pulling it out instead, how much I will lose the efficiency? If at all?

I’m planning a water-cooling system for my new PC and faced an issue. I’m going to use the top mount for the radiator (horizontal). Logically, it’s best to push the air up, so it goes through the radiator and leaves from the top of the case right away. However, in that case (pun intended), if I’m mounting the radiator on the top adding the fans below the radiator, the liquid ports can only face downwards.

That makes filling the circuit and getting rid of the air in it tricky. I don’t want tricky, I want to be able to fill and empty the circuit without half-disassembling it or turning the PC case around. So one possible solution is to mount fans in exhaust position, then add the radiator below them. That way I’ll make some space for L-shape fittings and the air will have a way to escape the radiator when filling it with liquid.

Surely there are air leaks between the radiator and the fans, but they are there either way. Judging the fan as a local static pressure gradient (voltage) and the radiator as a resistance (ohmage), it seems it should work both ways pretty much the same. However, it’s not as abstract as electric current, and the hydrodynamic effects I can’t account for.

## How to solve :

I know you bored from this bug, So we are here to help you! Take a deep breath and look at the explanation of your problem. We have many solutions to this problem, But we recommend you to use the first method because it is tested & true method that will 100% work for you.

### Method 1

EK Water Blocks did some actual experimenting comparing the CPU and GPU temperatures of push, pull and push-pull configurations. The temperature difference was usually 1°C or less, in favor of the pull configuration. Since you intend to go with a pull configuration, you’re good! (Though in my opinion, that 1 degree would not be worth worrying about either way.)

Note: Use and implement method 1 because this method fully tested our system.
Thank you 🙂