Some plumbing problems can wait, while others need a licensed plumber the same day. Call promptly if you see water where it should not be, such as a leaking supply line, a damp ceiling, or a water heater that is dripping, because these can damage floors and drywall quickly.
Slow drains in one fixture often point to a local clog you can clear with a plunger. When several drains back up at once, the issue is likely in the main line and needs professional equipment.
Watch for low water pressure across the house, discolored or rusty water, or a sudden jump in your water bill. Each can signal a hidden leak or failing pipe. Unusual sounds like banging when you close a valve are also worth a look.
For any gas line or sewer concern, shut off the supply if you can and contact a professional. Complex repairs without the right tools can turn a small fix into a larger one.