My pool plumber pressurized my piping for a few weeks before gunite at 30 psi. When the guys did gunite the pressure dropped to 15 psi. Two days later it was down to 4 psi and there was evidence of water leaking out of the skimmers into the pool. It has stayed at 4 psi for two days now but I am concerned because the pressure has dropped so low. Our GC says everything is ok. Is this normal or do we have a problem somewhere?