Since June 1 I have had a terrible time getting chlorine in my pool. After several trips to the pool store they said my stabilizer was too low. I added stabilizer and eventually the chlorine came back to where it is supposed to be. In the mean time I got algae in the pool because of no chlorine for so long I am assuming so they told me to add an algecide. For the past week I am back to no chlorine. The pool store is now telling me I have chlorine lock. My pool is 14,500 gallons with a sand filter and a chlorinator using 3" tabs. Here are my numbers:

Alkalinity: 110
PH: 7.4
Calcium: 400
Stabilizer: 135
Free Chlorine: 0
Total Chlorine: 0

I was told by the pool store to drain a 1/3rd or more water out of the pool and refill.

Do you have any other suggestions?