I paid the pool company to close my pool. I noticed this thumping type sound on occassion when I'd sit on my deck thinking it was coming from the woods somewhere. I went to check the pool equipment today and noticed it was coming from my equipment. I saw the white pvc pipe that has a screw on connector was not connected to the other end of the pipe. It was the pvc pipe to the steps and deep end and that pipe went to the heater.
Now is the closing messed up seeing how this pipe was not connected by the closers and is there air in there now or will the pipes freeze here in NY.. One I connected the white pvc pipe to the other end the occassional thumping sound stopped.