Don't fully drain a fiberglass pool.

You almost never need to empty it completely, and doing so risks the pool popping out of the ground or cracking the shell. Fiberglass pools are lightweight and rely on the surrounding ground and groundwater pressure to stay put. If you drain it, the empty shell can float or flex, causing expensive damage.

If you really need to drain for repairs or deep cleaning, keep it to about 50-70% max. Anything more than that, and you’re gambling with the water table. Check local groundwater level first — if it’s high, don’t drain at all. You’d want a plumber or pool pro to handle it.

When refilling, do it slowly. Add water at the shallow end, not direct onto the floor. And don’t let the skimmer run dry while filling. Just be patient — rushing it is the most common mistake.

Honestly, unless you’re replacing the liner or fixing a leak, just leave the water in there and use a sump pump to lower it a foot or two for cleaning.