Guide
Building a loop
A first custom loop takes about two hours to assemble and twelve to leak-test. Most of what goes wrong goes wrong before any of that, in the measuring and the parts list. This is the order we would do it in.
- 01
Measure the case before anything else
Radiator length plus fitting height is the number that decides the build, and it is not the number printed on the case spec sheet. A three-fan radiator needs its own length plus roughly 30 mm of fitting at each end. Measure the depth available behind the front panel too — a 30 mm core plus a 25 mm fan is 55 mm before a single screw goes in.
- 02
Pick the radiator first, then everything else
Cooling capacity is set by radiator area and fan speed, not by the block. A larger radiator does the same work at a lower fan speed, which is where quiet comes from. Start with the largest that fits, then choose a block, then a pump.
- 03
Soft tube for a first loop
Rigid tubing looks better and is a separate skill. Soft tube with compression fittings tolerates being moved, forgives a cut that is 5 mm long, and can be re-routed without a heat gun. Build the first loop in soft tube and learn the rest on the second one.
- 04
Count the fittings, then add two
Every tube run needs two. A simple CPU loop — reservoir to pump, pump to block, block to radiator, radiator to reservoir — is four runs and eight fittings. Angled adapters are extra on top of that, and running out of fittings mid-build is the most common reason a loop sits half-finished for a week.
- 05
Leak-test dry, with the system unpowered
Fill the loop, run the pump alone on a jumped power supply, and leave it twelve hours with paper towel under every joint. Nothing else in the machine gets power until that passes. This is the single step that separates a hobby from an expensive afternoon, and it is the one people skip.
The five that cause most of the failures
Over-tightening the fittings
The thread does not seal — an O-ring does. A compression fitting is finger-tight, and once the O-ring meets the block a quarter turn is the whole job. Using a tool is what cracks acrylic tops and what causes the leak it was meant to prevent.
Bending rigid tube cold
PETG forms at about 100 °C and cracks below that. Heat the whole bend zone evenly, use a silicone insert so the bore does not collapse, and use a mandrel — freehand bends look freehand.
Mixing aluminium into a copper loop
An aluminium radiator in a loop with copper blocks sets up a galvanic cell and destroys the aluminium part specifically, usually within months. Nothing in this catalog is aluminium on the wetted side, and nothing you add should be either.
Blaming the coolant for the tubing
Cloudy tube and a waxy film inside the blocks is usually plasticiser leaching out of soft PVC above about 38 °C, not a fault in the fluid. It gets blamed on the coolant because the deposit takes the coolant's colour. Plasticiser-stable tubing and clear fluid remove both the cause and the confusion.
Running dyed coolant through micro-fins
Pigment drops out of suspension and lands in the narrowest passage in the loop, which is the part you paid for. If you want colour, colour the tube, not the fluid.
A worked parts list
A single-radiator CPU loop in a mid-tower needs: one three-fan radiator, three fans, one CPU block in your socket, a pump and a top, a reservoir, eight compression fittings, two angled adapters, ten feet of soft tube and a litre of coolant.
Axiom 360 Loop Kit
$749.00That exact list, specified together and shipped in one box. The reason to buy it as a kit is not the saving — it is that the fitting count and the tube size are already right.
See what is in it →If you are unsure whether a part fits your case, ask before you order. Contact — we answer email within one business day.