Hello everyone, I'm coming up on my first pool opening season on about a 30 year old pool. Im draining the pool using a large water pump because I need to paint and try my best to make the pool look nice. The main drain is closed off because of a leak. I honestly have no idea if there is a hydrostatic valve. I'm going to wait until about June so I can get a nice dry period so hopefully there is less ground water. What precautions can I take to avoid heaving scenario. Its a concrete pool, can I drill holes to let ground water into pool? How do I drill holes underwater? Please help. Thank you.