CSLB C-36 Plumbing ContractorService, Repair, and MaintenanceMedium
A client reports that their basement floor drain is backing up with sudsy water whenever they run their washing machine. The other drains in the house appear to be functioning normally. What is the most likely cause of this specific issue?
- AA clogged branch drain line serving the laundry area.
- BA faulty check valve in the sump pump discharge line.
- CA blockage in the main sewer line leaving the house.
- DAn obstruction in the washing machine's standpipe or trap.
Show answer & explanationAnswer & explanation
Correct answer: A. A clogged branch drain line serving the laundry area.
Since the backup is specifically sudsy water from the washing machine and only affects the basement floor drain (which often shares a branch line with laundry), it indicates a blockage in the branch line serving that area, rather than the main sewer.
Why the other options are wrong
- B. A faulty sump pump check valve relates to groundwater removal, not the internal drainage of a washing machine or sudsy water.
- C. A main sewer line blockage would cause backup in lower fixtures throughout the house, not just isolated to laundry suds and the floor drain.
- D. An obstruction in the standpipe or trap would prevent the washing machine from draining, but wouldn't typically cause the floor drain to back up.
Laundry Drain Backup
When wastewater from a washing machine overflows or backs up, often due to blockages in the dedicated laundry drain or connected branch lines.
- Characterized by sudsy water backing up, often into a floor drain or the standpipe itself.
- Usually indicates a clog in the laundry branch line or the main sewer line.
- Can be exacerbated by excessive detergent use or lint accumulation.
Memory trick: Sudsy flows, where blockage goes.