On my small lathe, for cutting coolant, I use a small pond pump, which fills a tank and the excess overflows back into the reservoir. Thus I have a controllable constant height gravity fed system and the flow from the tank is controlled by a gas tap. Now I don't know what the demands for a water cooled spindle are, but my system is cheap and controllable and can easily supply up to 1.5 meters with a very small pump.

Just my two pennuth.

Cheers,

Rob