Using Pneumatic Fittings 8mm OD with Mora 420 and D5 Pump?

Hey everyone,

I'm working on an **SFF (Small Form Factor) PC build** and, due to severe space constraints, I **must** use **Legris Pneumatic Push-In Fittings (G1/4 to 8mm OD tube)** for all the internal connections.

I plan to cool a **Radeon 7900 XTX** (with an Alphacool Core Block) and a **Ryzen 7 7800X3D** (with an EKWB Velocity Block).

I already own a **D5 Next pump** and an **external MO-RA 420** radiator plus the above-mentioned hardware and water blocks that I intend to use. Crucially, my current external setup is so effective that I run the D5 Next at its lowest speed, around **1980 RPM**, achieving fantastic cooling results.

My main concerns revolve around the potential performance hit due to the small inner diameter of the 8mm tubing and the high restriction of the fittings themselves.

# My Core Questions:

1. **Flow Restriction:** The internal loop, constrained by the **8mm OD tubing** and the highly restrictive Legris fittings, will be a major bottleneck. Will my **single D5 Next**—especially running at the low speed of **≈1980 RPM**—be able to maintain an acceptable flow rate when pushing coolant through these highly restrictive components and the massive MO-RA 420? 2. **Cooling Performance:** How drastically will this small tubing affect the overall cooling performance of my high-end hardware (7900 XTX and 7800X3D)? Since the MO-RA 420 is a low-restriction beast, will the benefits of the huge radiator be effectively nullified if the flow rate drops critically low (e.g., below 90 L/h)? 3. **Pressure/Sealing Confidence:** The fittings are technically rated for much higher pressures (20+ bar). Have any of you had long-term experience with these pneumatic fittings in a low-pressure/PC water-cooling environment? Should I be concerned about leaks or any long-term issues, given the high restriction of the overall loop?

**Has anyone successfully used small diameter tubing (8mm OD) and high-restriction pneumatic fittings in a custom loop with a high-end pump/radiator setup like this?**

Thanks for your expertise!