How does watercooling help me to get a more quiet system?

The first message in this thread describes the system I'm planning to build: http://www.hardforum.com/showthread.php?t=1458328

A lot of guys say over at the Corsair forum that they get good cooling by using three fans in the top of the 800D case. And lots of other guys here and at the Corsair forum are watercooling with a three-fan radiator. So my question is: just how much more noise would an aircooled system be than a watercooled system?

Put another way, if I have to exhaust the same number of watts of heat, what is it about watercooling that means I need less total CFM of air moved through fans? For the 800D, does that mean I can use less powerful fans, or lower speed fans, in the top of the case?

I'm assuming here that noise is directly related to total CFM.

The only thing I can think of is that with watercooling, I don't need a fan on the CPU heatsink and possibly the GPU, if I watercool that. But unless I want a super-elaborate watercooled system, the RAM, mosfets, NB/SB, and hard drives will all be aircooled.

I hope I've explained my question clearly enough.

Basically, a radiator drastically increases the surface area available for heat exchange. Think about it this way, a heatsink the size of one 120mm fan cools effectively at high rpms. On a radiator, you get three times the surface area (not really, but good approximation for now) using three fans operating at low (inaudible) rpm levels. So yes you are removing the same amount of heat, however watercooling allows you to move the heat more efficiently to a larger surface area than using normal air cooling. Also one of the best reductions in noise you'll see is from your graphics card. No more 17 million rpm fans trying to squeeze air out of pci backplates

Water is something like 4x more effective and conducting heat than air is. It transfers faster and can carry a larger heat load provided there is sufficient volume. Single radiator systems sometimes have issues competing with higher end air cooling or at best are about as good as they are. Dual and triple radiator systems are much more effective.

Both Punk and Dan have summed it up well. Get a Swiftech MCR series radiator and slap some nice 50-60 CFM fans on there for a nice quiet setup.

Originally Posted by lollerskater69

Both Punk and Dan have summed it up well. Get a Swiftech MCR series radiator and slap some nice 50-60 CFM fans on there for a nice quiet setup.

Thanks. This answers my question.