A slow drain that is not entirely blocked is usually caused by a partial restriction or narrowing of the pipe interior due to a lining of congealed soap scum, hair strands, and body oils along the P-trap. While water can still force its way through the reduced opening, the flow rate is severely restricted, causing the sink or shower basin to drain sluggishly. Verification: Inspect the upper drain trap using a flashlight or clear out surface debris to test flow velocity.
1 votes
Marked as accepted