How long should I wait to swim after adding algaecide to my pool?

For most standard pool algaecides, wait 15-30 minutes — the chemical disperses and dilutes quickly. Check the label; concentrated or heavy-duty types may require up to 24 hours. Run the pump during that time. If you added chlorine or shock, wait until chlorine levels drop to 1–3 ppm. When in doubt, wait an hour.