Wont work with boiler unless you constantly have water draining out of it to make room for the water coming form your water cooler kit. Not to mention the rusting problem from using tap water.
Swimming pool water wouldn't last too long in a water cooler kit before it causes problems with corrosion and clogs the system.
But good idea's anyway.
You don't circulate the actual boiler water or pool water through the water cooling system, are you nuts?

Renewable energy boilers have heat exchangers, basically a copper coil inside the boiler, to which you hook up your water-cooling circuit on the outside. Heat from water-cooling gets exchanged with the (still cold) water in the boiler, and nothing more but thermal energy is exchanged. They are both closed, separate circuits, only in connection with each other via a thermal route. Hence there are no issues with rust, corrosion, clogging,... Same principle can be applied for a pool, a copper coil in the filter housing will give off heat to the water flowing past it.
This way you are only limited by the flow-rate and size of your boiler or swimming pool, in the case of a boiler it might get a little hot if you're out on vacation.
