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Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How is tap water not full of mold and algae when nobody cleans the inside of the pipes that carry it?

Anything wet that I leave outside accumulates mold, algae, and other gross stuff over time.  Given that drinking water pipes are not regularly flushed out with bleach or something, how is it that drinking water is not totally filthy from going through dirty pipes?

Edit: thanks for all the responses guys!  Especially from the water treatment and plumbing experts.  Didn't expect to get such a big reaction!
gpt
> drinking water pipes are not regularly flushed out with bleach or something

They are, essentially. Drinking water supplies contain a low concentration of chlorine bleach or another disinfectant to prevent germs growing.

Also the pipes are sealed, with valves and taps designed to prevent air containing germs being drawn in, and they're opaque so light algae need to grow doesn't get in.

EDIT: As many people have mentioned, not all places and countries leave the disinfectant in the water. Ensuring that it's clean when it enters the pipes - either with chemicals that are removed or with UV light - along with the pipes being airtight and dark and unfavourable to life is when done correctly enough to keep the water clean.