Why Sewers Back Up in Heavy Rain, and How Rosemead Homes Can Avoid It

Sewers back up in heavy rain when stormwater gets into a system built for wastewater. Downspouts, yard drains or a broken cleanout cap connected to the sewer can add a large volume of water at once. LA County asks homeowners to keep rainwater out of sewer lines because it can overwhelm their capacity.

In Rosemead, as in most of Los Angeles County, rain and sewage are meant to travel separately. Rain runs off roofs and streets into gutters, catch basins and the storm drain system. Wastewater from homes runs through laterals to the public sewer mains maintained by LA County Public Works. The sewer is sized for wastewater, not for storms.

When rainwater gets into the sewer, it competes for space in pipes that were never meant to carry it. A partial clog that the line could live with on a dry day suddenly becomes a backup.

The most common way is a direct connection: a downspout, an area drain on a patio or a yard drain tied into the sewer line. Another is a broken or missing cleanout cap in the yard, which lets runoff pour straight into the lateral. Cracked pipe and open joints let in groundwater too, especially when the soil is saturated.

Each source adds water at exactly the wrong time, when everyone nearby is also sending water down their drains and the system is already busy.

When the lateral cannot carry everything, water backs up to the lowest opening in the house, usually a shower or tub on the ground floor. That is often the first warning. If it happens during storms and not on dry days, rainwater is the prime suspect. A sewer camera inspection Rosemead can show cracks and open joints where groundwater gets in.

Stop using water in the house, keep people away from the affected drain and check the outdoor cleanout if it is safe. If the cleanout is full, the problem is likely in your lateral and a drain contractor can clear it. If sewage is coming out of a manhole in the street, report it to LA County Public Works at 800-675-HELP (4357). See emergency drain service Rosemead for the full checklist.

Once the line is flowing again, find out why it backed up. A camera inspection shows whether there was a clog, a crack letting in groundwater or simply more water than the line could carry. Fixing the source is cheaper than cleaning up after every storm.

Take ten minutes on a dry day to walk around the house. Follow each downspout and see where it ends: on a splash block, in a planter or the lawn, or into a pipe that disappears into the ground. A downspout that goes underground could connect to the storm drain, a dry well or, wrongly, the sewer. Look at any patio or yard drains and ask where they lead. Then find the outdoor cleanout and check that its cap is whole and screwed down.

If anything looks like it ties into the sewer, ask a provider to confirm with a camera or a simple dye test. Moving a downspout to the yard is usually a small job compared with cleaning up after a storm backup.

Even without direct connections, a lateral with cracks or open joints lets in water from saturated soil. During long wet spells that steady seepage adds to the flow. The fix is the same as for roots: find the defects on camera and repair or line them.

The best time to look at your lateral is before the rainy season, when a provider can clear any partial clog and check the cleanout cap. Homes in Garvey Avenue Rosemead drain cleaning calls with busy households benefit most, since a partly blocked line has less room to spare in a storm. Check the contractor's license with the CSLB license check.