Thanks for the quick reply.

Power powder is their best chlorine shock. 1lb treats 16500 gallons of water.

My pool is concrete. The pool has been opened since we bought the home in may and like a novice my first helping hand came from Lesiles. The filter is "american product Quantum cellular media filter". The specifications of filter are:

Filter square area: 360sq ft.
Max pressure: 50psi.

With the above spec, I think the pool capacity is approx 20000 gallons or more. right ? I really dont know the pool capacity.

Please let me know the steps to fix the problem