You can replace the AIO cooler inside the NZXT H1 ... so to speak

[Windows Central]

Best answer: The NZXT H1 uses a standard 140 mm AIO water-cooling solution, which can be replaced by an aftermarket kit, so long as the tubing will be fine in the cramped space. It's not recommended to do so, however, unless you know everything will fit.

Full story from the WindowsCentral blog...