Key takeaways
- Leak test any custom loop with the system powered off and the PSU disconnected from components, as water-cooling makers advise, and leave it running for the recommended time before powering the PC.
- Use coolant approved by your block and radiator makers to avoid corrosion or galvanic issues.
- Check that the radiator mounting screws do not penetrate the fins.
- Keep the pump accessible and make sure it never runs dry.
- Follow each maker’s manual, and consult an experienced builder if you are new to custom loops.
The Cooler Master NR200P V2 is the most cited ITX case for water cooling because it supports 280 mm radiators and tall GPUs, the Lian Li Q58 is a compact second choice, the Lian Li A4-H2O suits a 240 mm all-in-one build in a very small footprint, and the Fractal Design Terra is better treated as a case for air cooling or a minimal AIO. That ordering follows several buying guides, though some of them disagree on radiator figures, so confirm the numbers on each maker’s page.
ITX Cases for Water Cooling at a Glance
| Case | Best for | Key stated specs (reported) | Limits |
|---|---|---|---|
| Cooler Master NR200P / NR200P V2 | Custom loops and AIOs in a small case | Reportedly about 18 L; radiators up to 280 mm at the top or side; CPU cooler height to 155 mm; GPU length around 357 mm | Larger than other ITX options; side and top radiators compete with other mounts |
| Lian Li Q58 | Compact water-cooled build | Reportedly about 14.3 L with roughly 320 mm GPU clearance; radiator support is reported inconsistently as 240 or 280 mm | Confirm radiator size in the maker’s manual before buying parts |
| Lian Li A4-H2O | Small 240 mm AIO build | Reportedly about 11 L, 240 mm AIO support, GPU up to about 322 mm | Reported to have limited cooler height and little room for a full custom loop |
| Lian Li O11D Mini V2 | Roomy custom loops with a standard PSU | One guide notes full ATX PSU support and suitability for large triple-slot GPUs with a water block | Bigger than a true small-form-factor case |
| Fractal Design Terra | Air cooling or small AIO | Reportedly about 10.4 L, 322 mm GPU; sources describe 120 mm radiator positions | One report notes a side radiator reduces GPU length to about 200 mm |
Sources conflict on several of these specifications, particularly radiator sizes on the Q58 and Terra. Treat the table as a starting point and rely on the maker’s manual.
What Matters in an ITX Water-Cooled Build
Radiator size and position
A 240 or 280 mm radiator gives the best cooling in a compact case, but it takes up the volume that might otherwise host the GPU or PSU. Top-mounted radiators may collide with the motherboard’s tall VRM heatsinks or memory modules, so confirm clearance.
GPU length and thickness
Modern graphics cards are large. With a full-cover water block, the card becomes slimmer, which allows triple-slot GPUs to fit cases where the air-cooled version would not. Check both the GPU’s length and its power connector location against the case.
Pump and reservoir space
Custom loops need room for a pump, reservoir and tubing bends. Pump-reservoir combos save space. Soft tubing is easier in tight cases, while hard tubing demands careful planning.
PSU format
Most ITX cases need SFX or SFX-L power supplies. The NR200P accepts SFX and SFX-L, and the O11D Mini accepts standard ATX. A high-end graphics card needs a PSU with enough wattage and the right connector, so check the GPU maker’s recommendation.
Airflow
Even a water-cooled build still needs airflow for VRMs, memory and SSDs. Leave fans on the radiators and consider a small exhaust position.
Serviceability
Filling and draining a loop in a small case can be awkward. Choose a case where panels come off easily, and consider quick-disconnect fittings to remove the GPU without draining the system.
Case-by-Case Notes
Cooler Master NR200P V2
Guides name this case first for water cooling. A 280 mm radiator can sit on the top or side, with CPU cooler height up to 155 mm for air coolers and a long GPU range. At around 18 liters it is the largest of the group but still compact. Mesh panels help airflow, and the case is widely supported with accessories.
Lian Li Q58
Smaller than the NR200P, and PCGuide notes that its interior allows impressive water-cooling setups. The radiator support figure is where sources disagree, so read Lian Li’s specification and manual. If you plan to run a 280 mm radiator, confirm that before committing.
Lian Li A4-H2O
This tiny case is designed around a 240 mm AIO. It does not leave much room for a custom loop, and cooler height is limited. It suits builders who want a very small footprint and accept a standard all-in-one.
Lian Li O11D Mini V2
Not a true mini-ITX case, it supports ITX boards but offers far more space. It suits a large GPU with a water block and ATX PSU, if desk space allows.
Fractal Design Terra
A well-regarded design for its materials and small size, but sources agree it is the weakest for water cooling. Radiator spots are small, and a side radiator may cut GPU length. Use it for air or a compact AIO.
AIO vs Custom Loop in ITX
| Approach | Strengths | Trade-offs |
|---|---|---|
| AIO liquid cooler | Sealed, simple, supported by the maker | Limited to the CPU; fixed tube length |
| Custom loop for CPU only | Flexible routing, quieter at low load | Maintenance; leak risk if fittings are mishandled |
| Custom loop with CPU and GPU | Cools both major heat sources and slims the GPU | Complex in a small case; more fittings and compatibility checks |
Safety and Build Notes
- Leak test any custom loop with the system powered off and the PSU disconnected from components, as water-cooling makers advise, and leave it running for the recommended time before powering the PC.
- Use coolant approved by your block and radiator makers to avoid corrosion or galvanic issues.
- Check that the radiator mounting screws do not penetrate the fins.
- Keep the pump accessible and make sure it never runs dry.
- Follow each maker’s manual, and consult an experienced builder if you are new to custom loops.
Budget Tiers
Budget tier
Cooler Master NR200P V2 with a 240 or 280 mm AIO. It offers the best radiator support for the lowest outlay among the cases here.
Mid-range tier
Lian Li Q58 or A4-H2O for a more compact, premium-looking build with an AIO.
Premium tier
A custom loop in the NR200P V2 or O11D Mini V2, with a full-cover GPU block and pump-reservoir combo. Component cost rises quickly with blocks, fittings and tubing.
Pick X If… Decision Table
| Pick this | If you… |
|---|---|
| NR200P V2 | Want the strongest radiator support and the easiest build |
| Lian Li Q58 | Want a smaller case and will confirm the radiator size first |
| Lian Li A4-H2O | Want a very small build with a 240 mm AIO |
| O11D Mini V2 | Want a custom loop with a large GPU and ATX PSU |
| Fractal Terra | Plan on air cooling or a compact AIO |
Alternatives
- Sliger and other boutique ITX cases. Small makers offer water-cooling-focused designs, though availability varies.
- Micro-ATX cases. A micro-ATX board in a slightly larger case gives much more room for loops with little size penalty.
- Air cooling with a large tower cooler. A strong air cooler is simpler and avoids leak risk if cooling headroom is acceptable.
Planning Checklist
- List the CPU, motherboard, GPU and PSU you plan to use.
- Read the maker’s spec for radiator size and mounting positions.
- Measure the GPU length, thickness and power connector location.
- Check the CPU block or cooler against the memory and VRM heatsinks.
- Plan tubing paths and fill ports before assembly.
Component Fit Table for a Water-Cooled ITX Build
| Part | Constraint | Note |
|---|---|---|
| Motherboard | Mini-ITX, 170 x 170 mm | VRM heatsink height affects top radiator clearance |
| Memory | Low-profile modules | Tall RGB heatspreaders can collide with a top radiator |
| GPU | Length and slot thickness | A full-cover block reduces thickness to roughly two slots |
| PSU | SFX or SFX-L, or ATX in larger cases | Match connectors to the GPU, including 12V-2×6 where used |
| Fans | 120 mm or 140 mm, thickness varies | Slim fans free up space for push-pull on radiators |
| Fittings | Compression or push-fit | Plan bend radius and a fill port before closing the case |
Thermal Expectations
Water cooling in a small case reduces temperature on the cooled parts, but heat still ends up inside the chassis and must be exhausted. Reviewers commonly point out that a single 240 mm radiator can handle a modern CPU but may struggle if it also cools a high-power graphics card. Adding a GPU block in a small case often means choosing lower-power parts or accepting higher fan speeds. Compare the maker’s thermal design power figures for your CPU and GPU against the radiator capacity before choosing a loop.
For many builders, the sensible compromise is a CPU AIO paired with a graphics card that has an efficient air cooler, keeping complexity low while still gaining the quiet and compact benefits of a small build.
Maintenance deserves a mention as well. Custom loops need periodic coolant changes according to the coolant maker’s schedule, and radiators collect dust quickly in a small chassis. Choose a case where the dust filters are removable without disassembling the loop, and plan how you will drain the system before you need to swap a part.
Frequently Asked Questions
Can you run custom water cooling in an ITX case?
Yes, but space is tight. The NR200P V2 and O11D Mini V2 are the more spacious choices, while very small cases often limit builds to an AIO.
What radiator size fits in the NR200P V2?
Guides report support for radiators up to 280 mm at the top or side. Confirm with Cooler Master’s specification and consider the clearance of your motherboard and memory.
Is the Lian Li Q58 good for water cooling?
PCGuide notes its interior allows strong water-cooling setups, but radiator figures are reported inconsistently. Read Lian Li’s manual to confirm the supported size before ordering parts.
Does the Fractal Terra work with liquid cooling?
Sources describe 120 mm radiator positions, and a side radiator may limit GPU length. It is better suited to air cooling or a small AIO.
Do I need an SFX power supply?
Most ITX cases use SFX or SFX-L power supplies, though the O11D Mini V2 supports ATX. Check the case manual and choose wattage to match your GPU.
Is a custom loop worth it in a small case?
It can reduce GPU thickness and noise, but costs more and takes planning. Many builders find a 240 or 280 mm AIO delivers most of the benefit with less complexity.
