How often you should add water to your pool depends on how quickly the water evaporates. Keep an eye on your skimmer box, if you have one. Top up the water in your pool if you notice the water levels are lower than the bottom third of your skimmer. This helps prevent damage to your pump. 

Replace all the water in your pool every five to seven years, depending on how often you use your pool, the weather, and whether or not you close your pool for the winter.

It’s a good idea to wait at least 24 hours after opening your pool before you swim in it. Pool opening often involves shocking the water, and the chemical levels need to come down a bit before it’s safe to swim. You can continue testing your water pH and chlorine levels if you’re in a rush. It’s wise to wait until your chlorine levels drop to under four parts per million (ppm) and you have a water pH of between 7.2 and 7.8. You can artificially lower your water pH to speed up the process.

Generally, you do not need to drain your pool to convert it to a saltwater system. The main exception is if you have used an antibacterial agent containing polyhexamethylene biguanide to sanitize your pool, as these sanitation products do not mix well with saltwater systems. If this is the case, you will need to start fresh. You can either drain the pool or treat the existing water with a high dose of chlorine to remove the antibacterial agent. If you choose the chlorine treatment, wait several days to allow the chlorine to work before proceeding with the conversion. If you are unsure whether this applies to your pool, consult a pool technician.

Avoid the dreaded pool pop by only draining your pool during dry, temperate times of the year. If there is too much moisture or the threat of ice in the ground surrounding your pool, the pressure could disrupt the stability of your pool's floors and walls. Additionally, always open the hydrostatic drains in an inground pool toward the end of the design process.