If multiple drains in the house are slow, the issue is likely in your main sewer line. Maintenance Tips to Prevent Future Clogs
If the water rushes down the drain, you’ve succeeded! If it lingers, repeat the process 2 or 3 more times. Sometimes stubborn hair clogs require multiple rounds of pressure to break apart. When Plunging Doesn't Work unclog shower drain with plunger
If your shower has a (a metal cap that twists or pulls up), you need to remove it to get a good seal. If multiple drains in the house are slow,