WTF?! We've seen PC builds that prioritize performance, ones that focus on silence, and those that look like they belong in a cyberpunk art gallery. Billet Labs' latest project falls firmly into the latter – as usual. It's a custom passive water-cooled gaming PC with no fans, lots of copper, and enough heat to make its creator admit the internet might have had a point.
The build comes from Felix at Billet Labs, who set out to answer the question: can you cool more than 500W worth of modern PC hardware without any fans? The internet's usual answer to passive water cooling is that it is pointless and inefficient, but that wasn't going to stop someone who previously turned a century-old cast-iron radiator into a PC cooler.
This new system uses many of the same core parts as that earlier "Raddy" project, including a Ryzen 7 9800X3D, an RTX 5080, a Gigabyte Aorus Pro B850 motherboard, 32GB of RAM, 2TB of storage, and a 600W Flex ATX PSU. Raddy looked amazing, but it weighed around 100kg (220 pounds), needed regular flushing, and was not truly passive as it still had three fans.
For the new machine, Felix used three radiators: a 120 x 240mm unit, a 140 x 280mm radiator, and a much larger 200 x 400mm model. They were stacked above the components in a tapered tower designed to use the convection chimney effect. Hot air rises through the large lower radiator and continues upward through the smaller ones, theoretically pulling more air through the system without mechanical assistance.
The components sit on an 8mm aluminum base plate, while the loop uses polished copper pipework, brass fittings, a custom reservoir made from 54mm copper pipe, temperature and pressure gauges, and a prototype Billet Labs CPU block.
Felix even tried to turn the motherboard fully fanless by transferring heat through thick thermal pads into the aluminum base.
As is often the case with these ambitious custom builds, there were problems. One radiator was ruined when the mounting screws pierced its water channels, forcing Felix to strip and prepare a replacement.
Once assembled, filled, and running, the system was impressively quiet, with the pump becoming the loudest component once the motherboard fan was disabled and the pump speed was adjusted to around 80%.
The thermal testing started well enough. After around 30 minutes of idling, the water temperature settled in the high-20s Celsius, while lighter workloads such as Peggle were not enough to trouble the system. Cinebench was more demanding – after roughly half an hour, coolant temperatures climbed to just under 40C, while the Ryzen 7 9800X3D's cores averaged close to 90C.
Fan-less gaming PC - 5080/9800x3d/32gb/2tb - Yes I'll probably add fans next
by u/Billet_Labs in pcmasterrace
Gaming pushed the passive setup much harder. Halo 3, Clair Obscur: Expedition 33, and Cyberpunk 2077 all showed that the system could run real games without the RTX 5080 throttling, but the CPU was less comfortable, occasionally hitting 95C or more. Cyberpunk 2077 pulled close to 400W from the wall, with the CPU reaching the low-80s and the GPU sitting in the mid-70s.
The worst-case scenario came from running Cinebench and FurMark at the same time. That torture test pushed total system draw beyond 450W, sent coolant temperatures past 60C, and again caused the CPU to throttle. That 60C-plus water temperature is around the maximum rated level for the pump used in the build. The GPU still avoided throttling, though it reportedly reached the low 80s under the heaviest load.
Felix concluded that while the system technically worked, he had "failed to make a passive PC" he would want to use every day. He also suspects the smaller radiators might have hurt performance due to their denser fins, and plans to add a single 120mm fan in a follow-up.
If you're interested in other Billet Labs creations, check out this miniature RTX 4090-powered PC that looks like an old alcohol distillery.