Your pool foam is probably a chemistry problem.

Usually, yes. Low calcium hardness or high phosphates from sunscreen, sweat, and leaves are the main suspects. Too much algaecide can also cause it.

Foam forms when water gets too soft (low calcium) or when organic stuff breaks down and creates surfactants—basically, soap-like compounds. That’s why you see it after a pool party or heavy rain.

The fix isn’t complicated: test your water first. Add calcium hardness increaser if it’s low. If phosphates are high, use a phosphate remover. Shock the pool to break down organics. A little clarifier or a filter rinse helps push out the crud. Most foam disappears after a good filter run.

Don’t drain and refill unless it’s really bad—that’s the nuclear option. Start with a test kit.