Evaluate the specific situation Identify the influenced drain and extent of backup Verify if multiple drains are influenced (indicates key line problem) Try to look for visible drinking water damage or overflow Standard Do it yourself Measures Pour boiling h2o down drain Use plunger appropriate for sink/bathroom Test baking soda https://www.kawatan.net/why-you-should-never-use-baking-soda-and-vinegar-to-unclog-a-drain/