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How to fill a water cooled PC?

Published in Uncategorized 6 mins read

To effectively fill a water cooled PC, ensure all components are securely connected and the system is leak-tested before slowly introducing coolant into the reservoir. Then, carefully bleed any trapped air from the loop by tilting the PC and cycling the pump until the fluid level stabilizes and no more bubbles appear.

Introduction to Filling Your Custom Liquid Cooling Loop

Filling your custom liquid cooling loop is a critical step in building or maintaining a water-cooled PC. A proper fill ensures optimal thermal performance, prevents damage from air pockets, and extends the lifespan of your components. This guide will walk you through the process, from initial preparation to final checks.

Essential Tools and Preparations

Before you begin filling, gather all necessary tools and prepare your system. This minimizes interruptions and ensures a smooth process.

Tools You'll Need:

  • Coolant: Specifically designed for PC liquid cooling systems.
  • Funnel: To prevent spills when pouring coolant into the reservoir.
  • Paper Towels or Microfiber Cloths: For immediate cleanup of any spills.
  • PSU Jumper (24-pin ATX bridge): To power on the pump without booting the PC.
  • Distilled Water (Optional): For initial flushing or if you need to dilute concentrate.
  • Zip Ties or Cable Management Straps (Optional): To manage cables for better access.

Pre-Fill Checklist:

  1. System Powered Off: Absolutely ensure your PC is completely powered down and unplugged from the wall.
  2. Leak Testing (Air Pressure): While not strictly part of filling, it's highly recommended to perform an air pressure leak test before introducing any liquid. This uses a specialized pump to pressurize the loop and detect leaks.
  3. All Fittings Secured: Double-check every single fitting, clamp, and connection in your loop. If you've previously drained your system for maintenance or upgrades, ensure any drain tubes or specific fittings that were disconnected have been fully reconnected and secured to restore the loop to its original, sealed state before adding new liquid. A loose connection can lead to catastrophic leaks.
  4. Components Connected (Except GPU/Storage for Safety): For the initial fill and leak test, it's often advisable to have the graphics card and storage drives disconnected from power to minimize potential damage in case of a leak. The motherboard and pump should remain connected to the PSU.
  5. Reservoir Accessible: Ensure you have clear access to your reservoir's fill port.

Step-by-Step Guide to Filling Your PC Water Cooling System

Follow these steps carefully to ensure a clean, efficient fill.

Step 1: Prepare the Reservoir

Locate the fill port on your reservoir. This is typically at the top. Unscrew the cap and place your funnel securely into the opening.

Step 2: Begin Filling with Coolant

Slowly pour the coolant into the reservoir. Only fill it partially, leaving some room at the top. The coolant level will drop significantly as it begins to fill the empty tubing and components.

Step 3: Initial Pump Priming & Air Bleeding

This step focuses on getting the pump running and circulating fluid, beginning the air-bleeding process.

  1. Isolate the Pump: Ensure only the pump is connected to the power supply. Use your 24-pin ATX jumper to short the green wire with any black wire on the main ATX cable. This will power on the PSU and pump without booting the PC.
  2. Start and Stop the Pump: Briefly turn on the PSU (and thus the pump) for a few seconds, then turn it off. This helps push fluid through the loop and dislodge large air bubbles.
  3. Refill Reservoir: As the coolant level drops in the reservoir, continue to top it off. Never let the pump run dry, as this can damage it.
  4. Repeat: Continue this cycle of briefly running the pump and refilling the reservoir until the loop is mostly full and the coolant level in the reservoir stabilizes.

Step 4: Full System Air Bleeding

Once the initial fill is complete, it's time to purge the remaining air.

  1. Run the Pump Continuously: With the loop mostly full, let the pump run continuously (via the PSU jumper).
  2. Gently Tilt the PC: Carefully and slowly tilt your PC in various directions (forward, backward, left, right). This helps move stubborn air bubbles trapped in radiators, blocks, and tubing towards the reservoir.
  3. Monitor Air Bubbles: Watch the reservoir for air bubbles exiting the loop. As they appear, the coolant level may drop, so continue to top off the reservoir as needed.
  4. Patience is Key: This process can take anywhere from a few minutes to several hours. For best results, allow the pump to run for at least 2-4 hours, or even overnight, to ensure all air is purged. You'll know it's done when no new bubbles appear in the reservoir and the coolant level remains stable.
  5. Shake Gently (Optional): For very stubborn bubbles, a very gentle shake of the PC might help dislodge them, but be extremely careful.

Step 5: Final Top-Off and Sealing

Once all air is bled and the fluid level is stable:

  1. Top Off Reservoir: Fill the reservoir to the recommended maximum fill line (or just below the fill port, leaving a small air gap for expansion).
  2. Secure Fill Port: Replace the reservoir cap and tighten it securely, but do not overtighten.
  3. Inspect for Leaks Again: Perform a final visual inspection for any leaks before connecting all power cables and booting the PC.

Tips for a Successful Fill

  • Patience: Rushing the filling and bleeding process is the most common cause of issues. Take your time.
  • Leak Detection: After the initial fill and bleeding, leave paper towels under potential leak points for a few hours or even overnight as a precautionary measure.
  • Coolant Choice: Always use coolants specifically designed for PC liquid cooling. Automotive coolants or plain distilled water without biocides/corrosion inhibitors can cause issues. For more details on coolant types, check out this guide on EKWB's blog.
  • Keep it Clean: Work in a clean environment to prevent dust or debris from entering your loop.
  • Regular Maintenance: Plan to drain, flush, and refill your loop periodically, typically every 6-12 months, depending on your coolant type and usage.

Common Issues and Troubleshooting

Issue Possible Cause Solution
Persistent Air Bubbles Trapped air in specific components/radiators Continue tilting the PC in different directions. Run the pump at varying speeds if your pump supports it. Let the pump run for an extended period (several hours or overnight). Gently tap components to dislodge bubbles.
Leaks Loose fittings, damaged O-rings, cracked components Immediately power off and unplug the PC. Identify the source of the leak. Tighten the fitting, replace the O-ring, or replace the damaged component. Re-test thoroughly before powering on the PC. For further help, refer to resources like this Corsair guide on custom liquid cooling.
Pump Not Priming/Flowing Air lock, pump not receiving power, faulty pump Ensure the pump is properly connected to power (use PSU jumper). Fill the reservoir adequately. Briefly turn the pump on and off repeatedly to break an air lock. If all else fails, the pump may be faulty and require replacement.

Liquid Cooling Maintenance