PC coolant expansion

[artag]

I'm building a system that uses warm circulating water to keep a constant temperature.

I've allowed for a pump, heater, filter, reservoir and a partitioned expansion chamber as used in hot water systems. But I may make a smaller one using PC watercooling parts and it made me wonder - how do they allow for the coolant to expand as it warms up ? I don't think they're generally open, and while some pump types have a reservoir that might trap a bit of air it seems like you'd at the very least need to carefully bleed it after moving.

Or are they so small that a few bits of flexible hose will take up the slack ?
 

[Phil1977]

A few bits of flexible hose and a few unavoidable air/gas bubbles do the trick.

Some better systems have a pressurizer or use little balls of compressible balls.