while this looks like it could be an easy enough fix I would do nothing untill I found the outside shut off. Call the water dept. and ask for help finding it. You may also need a shut off thing to get to it. Unless there is a floor drain that can handle mass water if that thing breaks you will be up &%¢∞§¶ creek in a big hurry.
You will want to know where the outside shut off is anyway
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