Should I drain my pool?

No. Green algae is a water problem, and water problems clear with chemistry and filtration: lower the pH, shock hard, brush and run the filter. How to get algae out of a pool has the full order of operations.

The exception is when the algae or the staining is in the plaster rather than the water. Black algae rooted into the surface and stains that will not lift chemically need a drain and an acid wash. That is a different job from clearing green water.

Because the water table is high, and groundwater pushes up on the shell from underneath. A full pool's weight holds it down. Empty it and that pressure can crack the floor or lift the whole shell, and a pool that pops out of the ground is a rebuild, not a repair.

Many pools here have a hydrostatic relief valve in the floor to let groundwater in rather than letting it push the shell up, and whoever drains the pool needs to open and check it. The risk is highest in the rainy season, after heavy rain, and in low lying yards. That is why a drain for an acid wash should be as short as the job allows, and timed for drier weather where possible.

Only when the water or the surface cannot be fixed with the pool full:

• An acid wash or resurface. Both need the plaster exposed.
• Stabilizer that has built up too high. There is no chemical that removes cyanuric acid. Replacing some of the water is the only fix.
• Water that will not balance. Very high calcium or dissolved solids after years of evaporation and top ups.
• Contamination you cannot treat, such as a large amount of flood water.

For the stabilizer and balance problems, a partial drain is usually enough.

Yes, and for most chemistry problems it is the better option. Lowering the level a foot or two and refilling dilutes stabilizer, salt or calcium while leaving enough water in to keep the shell weighted down. It can be repeated if one round is not enough.

Test the fill water first if it comes from a well, because refilling with metal laden water can trade one problem for another.

Only enough to keep it from overflowing onto the deck or into the equipment, and then only a few inches. A full pool is fine in heavy rain. Draining it low to make room for a storm is exactly the wrong move here, for the reason above.

No. That is the one that costs people the most money. Leave it full, lower it a few inches at most, and shut the equipment off at the breaker. The rest is in our hurricane season pool checklist.

Rarely, and in a well kept Florida pool sometimes never. Rain does a fair amount of the water replacement for you every summer. Drain when the water cannot be balanced or the surface needs work, not on a schedule.