What happens when you change AIO coolant

An all-in-one (AIO) liquid cooler circulates coolant through a sealed loop to pull heat away from your CPU or GPU. Over time — usually two to five years depending on the cooler model — that coolant degrades, becomes less effective at absorbing heat, and can develop algae or mineral buildup inside the tubes. Changing the coolant restores cooling performance and extends the life of the cooler.

Most AIO coolers are sealed units designed to run for years without maintenance. Some models allow you to refill or fully drain and replace the coolant; others are not designed to be opened at all. Before you start, check your cooler's manual or manufacturer website to confirm whether coolant changes are supported. If your cooler is sealed and not user-serviceable, replacing the entire unit is the safer choice.

Key Takeaways

  • Check your cooler's manual first — many AIO coolers are sealed and not meant to be opened by users.
  • If your cooler supports coolant changes, you will need distilled water, a small funnel, paper towels, and a container to catch old coolant.
  • Power down your system completely and let it cool for at least 30 minutes before opening any part of the cooler.
  • Drain the old coolant slowly into a container, refill with distilled water mixed with coolant additive if recommended, and bleed air from the loop by tilting the cooler while it runs.
  • Monitor temperatures for the first few hours after refilling to make sure the new coolant is circulating properly.

Check your cooler model and manual first

Not all AIO coolers are designed for user maintenance. Some brands like NZXT, Corsair, and Lian Li make coolers with user-accessible fill ports or drain plugs; others seal the loop completely at the factory. Opening a sealed cooler can damage the pump, introduce air into the loop, or void the warranty.

Look up your exact cooler model on the manufacturer's website and download the manual. Search for words like "refill," "drain," "maintenance," or "coolant change." If the manual does not mention these steps, the cooler is sealed. In that case, your only option is to replace the entire unit when performance drops.

Gather your supplies and prepare your workspace

If your cooler supports coolant changes, collect these items before you start: distilled water (not tap water, which contains minerals that clog the loop), a small funnel with a narrow spout, paper towels or a cloth, a small container to catch old coolant, and a flashlight or headlamp. Some coolers come with coolant additive packets; if yours did, have that ready too.

Work on a clean, flat surface with good lighting. Shut down your computer completely and unplug the power cable. Wait at least 30 minutes for the system to cool — the coolant inside can be hot enough to burn your skin. Remove the side panel of your case and locate the fill port or drain plug on your cooler's reservoir or pump head. This is usually a small cap or screw-on fitting on top of the pump.

Drain the old coolant safely

Place your collection container under the drain plug or fill port. If your cooler has a dedicated drain plug (usually at the lowest point of the loop), open it slowly and let the old coolant flow out. This can take several minutes. If there is no drain plug, you may need to carefully unscrew the fill port cap and tilt the cooler to pour the coolant out through the opening — work slowly to avoid spilling.

Once the coolant stops flowing, tilt the cooler in different directions to encourage any remaining liquid to drain. You do not need to get every last drop, but the more old coolant you remove, the better the new coolant will perform. Wipe up any spills immediately with paper towels. Do not pour old coolant down the drain; check your local regulations for proper disposal, as some coolants contain additives that require special handling.

Refill with distilled water and additive

If your cooler came with coolant additive packets, mix one packet with distilled water according to the instructions on the packet. If no additive was included, use distilled water alone — it is safe for the loop and will work, though some users prefer to add a small amount of coolant additive to inhibit algae growth and protect against corrosion. Use only distilled water, never tap water or filtered water, because minerals in tap water will accumulate inside the loop and reduce cooling efficiency.

Attach your small funnel to the fill port and pour the new coolant slowly into the reservoir. Fill it until the liquid reaches the fill line marked on the reservoir, or until it is about three-quarters full if there is no line. Do not overfill — the coolant needs room to expand as it heats up. Screw the fill port cap back on tightly.

Bleed air from the loop and test

Air pockets in the loop will reduce cooling performance and can cause the pump to make noise. To remove air, power on your system and let it run for two to three minutes. Then power it off, wait a minute, and tilt the cooler gently in different directions — forward, backward, and side to side — while it is off. This helps trapped air bubbles rise toward the fill port. Power it back on and repeat this process two or three times.

While the cooler is running, listen for unusual sounds like grinding or loud gurgling, which can indicate air is still trapped. If you hear these sounds, repeat the tilting and running cycle. Once the noise stops and the pump sounds normal, let the system run for at least an hour and monitor your CPU or GPU temperatures using software like HWiNFO or your cooler's control software. Temperatures should be similar to what you saw before the coolant change, or slightly lower. If temperatures are significantly higher than before, air may still be trapped in the loop — repeat the bleeding process.

Frequently Asked Questions

Can I use tap water or bottled drinking water instead of distilled water?

No. Tap water contains minerals like calcium and magnesium that build up inside the loop and reduce cooling performance over time. Bottled drinking water is also not pure enough. Use only distilled water, which you can buy at any grocery store or pharmacy for a few dollars.

What if my cooler does not have a fill port or drain plug?

Your cooler is sealed and not designed for user maintenance. Attempting to open it can damage the pump or introduce air into the loop. Replace the entire cooler when performance drops. Most sealed AIO coolers last five to seven years before coolant degradation becomes noticeable.

How often should I change the coolant?

Most AIO coolers run for three to five years before coolant degradation noticeably affects cooling performance. If your temperatures are rising but your cooler is clean and the fans are working, coolant change may help. If you have not changed it in more than five years, it is worth trying.

My cooler is making a grinding noise after I refilled it. What do I do?

This usually means air is trapped in the pump. Power off the system, wait one minute, then tilt the cooler in different directions while it is off. Power it back on and listen. Repeat this cycle three to four times. If the noise continues, the pump may be damaged — contact the manufacturer about a replacement.

Can I mix different brands of coolant or additive?

Stick with the additive that came with your cooler, or use distilled water alone. Mixing different brands of additives can cause chemical reactions that cloud the coolant or damage seals inside the loop. If you do not have the original additive, plain distilled water is the safest choice.