I live in an apartment in an old building. Recently the water froze and ever since the plumbers fixed it the water comes out reddish brown and you can see stuff in it. The problem will clear up for a few days and then the water will turn color again. Why is this happening? Is it safe for us to drink and our pets?

Sounds like they've stirred up somr rust in the old steel lines. It should eventually clear up.

Harmful? Probably doesn't taste good. Probably will stain your clothes, if you wash them there.

Regards,
Stew