Brief Answer:
Give some anti-emetic with acid reducing agent

Detailed Answer:
Hello

Thanks for asking on this platform

Vomiting after ingestion of swimming pool water is a common complaint and can be due to gastritis or some infection.
Although chlorine is used to kill germs but still some germs can be left causing stomach problems. Chlorine itself may also cause stomach upset.
Here I would suggest you to give some anti-emetic like ondensetron and acid reducing agent like omeprazole/lansoprazole to control vomiting.
Give plenty of fluids once the vomit gets controlled to avoid dehydration.Most of the time symptoms subside within a day or two after giving these medicines.
If condition worsens or vomiting persists even after giving these medication, consult a physician for proper evaluation and to consider about the need of antibiotic.

I hope this helps.
Please let me know if you have any more queries.
Wishing for your child good health.
Regards

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