Home made pool heater?

[bell9440]

I am think of making a pool heater out of a water heater.I would cut the end out of the tank and make a coil out of copper tube inside it.So the water in the water heater would stay a bought 130% and the pool water would run threw the coil and transfer the heat.It shouldn't cost anymore to run than a normal water heater.What do you guys think?Has anyone tried this before?