can i use water as coolant

Yes, technically you can use water as a coolant. However, you should note that water, while it has excellent properties for heat transfer, it also has several disadvantages when used as a coolant. For starters, water can cause rust and corrosion in metallic components of your engine. Additionally, using water might lead to freezing in colder temperatures.

The same principles apply. Using water in a computer's liquid cooling system can indeed lead to corrosion and damage over time. That's why liquid cooling systems often use mixtures of water and other substances such as propylene glycol or ethylene glycol, which help to prevent corrosion, inhibit the growth of algae, and lower the freezing point.

Distilled water is actually preferable to tap water if you choose to use water as a coolant since it does not contain the minerals that lead to scale build-up. However, it still doesn't prevent the issues of corrosion and potential freezing, which is why coolants typically contain additional chemicals like anti-corrosives and anti-freeze.

The best option would be to use specially designed coolants with the apt mix of anti-corrosive agents, anti-freeze additives, and other substances to prevent any sort of operational issues with your system such as overheating or freezing. Always refer to the manufacturer's guidelines to find out the best coolant to use for your specific circumstances.