Conventional cooling solutions don’t cut it when dealing with a server cluster that kicks out 8,000 watts of heat. LTT’s “million dollar PC” (a wild nine-server cluster with two petabytes of NVMe storage) was turning their server room into a sauna, and their makeshift cooling tower setup, while functional, was creating as many problems as it solved.
The original setup was a disaster waiting to happen: a massive cooling tower taking up precious space, cardboard ducts channeling hot air (hello, fire hazard), and a weak cast iron pump in a mixed metal loop with no corrosion inhibitors. Something had to change.
Why Traditional Solutions Weren’t Working
The proof-of-concept heat exchanger setup was functional but deeply flawed. Linus had cobbled together a pair of APC data center cooling towers that we found behind a local data center, but they were:
- Taking up an ungodly amount of space in our already cramped server room
- Positioned incorrectly – they’re designed to go between racks, not behind them
- Connected via cardboard ducting that was both inefficient and potentially dangerous
The fundamental problem was that we were trying to adapt equipment designed for proper data centers with hot and cold aisles into our closet-sized server room. It was like trying to fit a jet engine into a compact car – technically possible, but hardly practical.
The Water Door Concept
The solution seemed obvious in hindsight: why not attach radiators directly to the back of the rack? This would reclaim the space and likely work better by capturing heat at the source. Thus, the “water door” concept was born.
The idea was simple but brilliant – replace the standard back door of the server rack with a custom-built door featuring water-cooled radiators that would capture the heat as it exited the servers.
Of course, implementing this solution meant navigating a maze of plumbing challenges, from finding the right fittings (who knew 5/8″ copper pipe was only used in HVAC applications?) to reforming damaged pipes with a socket and hammer not to mention the constant threat of leaks that could destroy thousands of dollars of equipment.
Building the Water Door
The construction process was a comedy of errors and improvisation. They salvaged radiators from the cooling towers (after discovering that buying new ones would cost upwards of $60,000), soldered fittings onto them, and mounted them to a door frame.
The plumbing setup was particularly challenging. We needed to:
- Create a system that could handle the door opening and closing (hence the swivel barbs)
- Ensure no leaks at any connection points
- Replace the weak cast-iron pump with a more powerful stainless steel one
- Create a system to direct airflow through the radiators
They finally had a working water door after several false starts, leaks, and fixes. The moment of truth came when they closed it, turned on the water, and felt the air coming through—it was actually cool! The hot air from the servers was being effectively captured by the radiators, and the heat was transferred to the water, which was then pumped out to be cooled elsewhere.
The Results
The difference was dramatic. Opening the door revealed a blast of 50-60°C air from the servers, but closing it resulted in a much cooler 30-35°C output. They had created a functional water-cooling system that not only reclaimed the space but actually performed better than the previous setup.
After running for several hours, the server room temperature stabilized at about 30.5°C – a degree or two lower than before, despite using less space. The thermal camera confirmed that while the servers were still running hot (around 50°C at the back), the water door effectively captured and removed that heat.
The best part? No professional data center would ever implement something this janky, which makes it fun. Our DIY solution might not be pretty, but it works, and it’s a testament to what you can accomplish with creativity, persistence, and a willingness to get your hands wet.
Next, LTT will add more fans to improve airflow through the radiators and move the cooling tower we removed from the server room up to the mezzanine for even better results. But for now, I’m happy to see how you can reclaim your space and slightly improve the cooling situation.
Frequently Asked Questions
Q: Why not use a commercial cooling solution instead of this DIY approach?
Commercial solutions for this level of cooling can be prohibitively expensive – we found that proper radiator doors would cost upwards of $60,000. The DIY approach allowed us to repurpose equipment we already had while creating a solution tailored to our specific needs at a fraction of the cost.
Q: Is there a risk of water leaking onto the servers?
Absolutely, which is why we took extensive precautions, we pressure-tested all connections before installation, used proper fittings and soldering techniques, and added valves to isolate sections of the system. While there’s always some risk with water cooling near electronics, the benefits outweighed the potential dangers in our situation.
Q: How much heat can this water door system actually remove?
Our server cluster generates approximately 7,000-8,000 watts of heat. While our water door doesn’t remove all of this heat (the room still runs warmer than ideal), it successfully reduced the ambient temperature by 1-2°C compared to our previous cooling tower setup, taking up significantly less space.
Q: Would this solution work for a home server setup?
For most home server setups, this would be overkill. However, the principles could be applied at a smaller scale. Suppose you’re running multiple high-performance servers at home that generate significant heat. In that case, a scaled-down version of this approach might be worth considering, though conventional cooling solutions would likely be more practical.
Q: What improvements could be made to this system?
Several enhancements could make this system even more effective: adding more fans to improve airflow through the radiators, creating better air ducting to ensure all hot air passes through the radiators, adding corrosion inhibitors to the water loop, and implementing a more sophisticated control system to adjust cooling based on server load and temperature.
Finn is an expert news reporter at DevX. He writes on what top experts are saying.
