The most efficient and comfortable way to heat a pool is by imbedding
the tubing in the floor and walls of the pool.

  EFFICIENCY; this is by far the most efficient way to heat a pool, you do not need to keep the water as hot because all of the surfaces are warm, there is no turbulence, so the surface loss is much less. This reduces the surface-to-air ratio that can sap pools of their heat. Also the fact that the pool pumping system does not have to run to heat the pool saves electricity.
  HUMIDITY; The lack of turbulence and lower surface temperature , considerably reduces the humidity.
 
COMFORT; The water is the same temperature from top to bottom, unlike standard pool heaters that layer the hot water near the top.
  SAFETY; Adding radiant heat to the surrounding pool area reduces surface water around the pool area and increases safety.
  In addition to being more efficient, radiant heat systems have many other benefits. They are not vulnerable to damage from chemically treated water. The system uses antifreeze, it doesn't need to be winterized. And the pool can be heated to prevent damage from freezing.

http://ingramswaterandair.com/

IN GROUND POOLS SHOULD BE WELL INSULATED

Expansion Tank

ALL PLUMBING MUST BE PEX OR COPPER OR BRASS