When sewage comes up through a shower drain, a floor drain or the lowest toilet in the house, the problem is almost never inside the bathroom. It is in the main line, the pipe that carries everything from your house to the public sewer. Heavy rain is one of the most common triggers in Northern California, and the first storms of the season are when a lot of homeowners find out their line has been failing for years.
Signs the main sewer line is backing up
A single slow sink is usually a clog in that fixture’s drain. A main line problem shows up in more than one place at once:
- Water comes up in the shower or tub when you flush a toilet or run the washing machine.
- The lowest drains in the house, often a downstairs shower or a floor drain, back up first.
- Toilets gurgle or bubble when another fixture drains.
- Several drains slow down at the same time.
- You notice sewage odor or soggy ground near the cleanout or over the line in the yard.
If more than one drain is affected, treat it as a main line problem.
What to do in the first hour
- Stop using water. Every flush, shower and load of laundry adds to the water that is already backing up into the house.
- Keep children and pets away from the water. Sewage carries germs that commonly cause stomach illness and skin infections.
- If water is standing anywhere near outlets, cords or appliances, turn off power to that area at the panel before you go near it.
- Do not touch sewage with bare hands. If you have to move things, wear waterproof gloves, boots and eye protection, and never mix bleach with ammonia while cleaning.
- Call a plumber to clear the line and find the cause. Clearing the blockage gets water flowing again. Finding out why it happened is what keeps it from happening again.
Porous things that soaked up sewage, such as carpet and pad, upholstered furniture, mattresses and cardboard, generally need to be thrown away, because health departments say they are too hard to clean.
Why heavy rain causes sewer backups
Sewer pipes are meant to carry wastewater only, but during storms rainwater finds its way in. The City of San Rafael says private laterals let in “massive amounts of stormwater” during large storms. That can overwhelm the system and push sewage back up into streets and homes. Sonoma Water describes the same problem with stormwater coming in through cracked or improperly connected private laterals.
The same weak points cause trouble in your own line:
- Tree roots find their way into joints and cracks, and the debris they catch builds into a blockage. When the rain arrives, the extra water has nowhere to go.
- Older clay and cast iron lines crack and shift over time. Groundwater and rainwater get in, and soil and debris come with them.
- Where a section of pipe has settled, waste collects and the line slowly loses capacity.
- A line that has partly collapsed may still drain on dry days, then fail as soon as flow goes up.
If your line backs up every winter, it is usually telling you about one of these.
Who is responsible for the sewer line?
In most of our service area the homeowner owns the lateral, the pipe that runs from the house to the public sewer main.
- Santa Cruz County Sanitation District: “You own and are responsible for your sewer lateral from where it connects to the public sewer main” all the way to your building. The district asks for overflows to be reported immediately. When a property has more than two overflows within a 12 month period, a video inspection is required.
- City of Santa Cruz: maintaining the private lateral, including the part under the street and the connection to the main, is the property owner’s responsibility. The owner is held liable for a spill caused by a problem in the building sewer.
- San Rafael: maintaining and repairing the lateral is the property owner’s responsibility.
If you are selling, remodeling or adding an ADU in the Santa Cruz County Sanitation District, the lateral also has its own inspection rules. They are covered on our sewer line repair and replacement page and our Santa Cruz sewer lateral inspection guide.
Does homeowners insurance cover a sewer backup?
Usually not under a standard policy. Standard homeowners policies generally exclude backup of sewers and drains. Insurers commonly sell coverage for it as a separate endorsement added to the policy, and what that endorsement covers varies. Some cover only damage inside the house, and some also cover the line. If you are not sure what you have, check your policy for a sewer or water backup endorsement before you need it.
How we find the cause and fix it
We put a camera in the line first. The footage shows what is happening inside the pipe: roots, cracked or offset joints, low spots and collapsed sections. We show you what we see before we recommend anything, so the recommendation is based on the pipe and not on a guess. More on sewer camera inspections.
What the camera finds decides the job:
- A blockage in a sound pipe can often be cleared and cleaned. Roots and buildup can be cut out, and hydro jetting scours the inside of the line.
- One damaged section can often be repaired on its own.
- A line that is failing along its length is usually better replaced than patched again. Where the line allows it, trenchless repair replaces the pipe through small access points instead of a full trench.
The diagnostic visit is $189, and we waive it if you go ahead with the repair. Home Protection Plan members pay nothing for it. We do not charge by the hour. Once we know what is wrong, you get a written upfront price before any work begins.
We answer the phone at any hour. Most of the time we can reach your home within a few hours, and sooner when sewage is backing up. Evenings and weekends cost more than a weekday visit, and we tell you the after hours rate when you call, not after we arrive.
Can you stop it happening again?
Fixing the cracked or root-filled section the camera finds is the most reliable way to stop a repeat. Two other things help:
- A backwater valve. The plumbing code calls for a backwater valve where fixtures sit on a floor level below the next upstream manhole cover of the public sewer. The valve lets wastewater leave the house and closes when sewage tries to come back in. If your lowest drains back up when the public sewer surcharges, ask whether your home should have one.
- Regular inspection of an older line. A camera inspection before the rainy season shows roots and cracks while they are still small.
If your drains are already backing up, book a sewer line repair visit and we will find out what is in the pipe.
Frequently asked questions
Why does my sewer back up when it rains?
Rainwater gets into sewer pipes through cracks, separated joints and root intrusion, in your own line and in other laterals connected to the public sewer. The extra flow fills a line that is already partly blocked or damaged, and the water comes up through the lowest drains in the house.
What should I do first if sewage is backing up into my house?
Stop using water, keep children and pets away, turn off power to any area where water is near outlets or appliances, and do not touch sewage with bare hands. Then call a plumber to clear the line and find the cause.
Who is responsible for a sewer backup on my property?
In most of our service area the homeowner owns and maintains the sewer lateral from the house to where it connects to the public sewer main. In the Santa Cruz County Sanitation District, overflows must be reported to the district immediately.
Does homeowners insurance cover sewer backup?
A standard homeowners policy generally does not. Coverage for sewer and drain backup is usually sold as a separate endorsement, and what it covers varies by insurer, so check your policy.
What does it cost to find out what is causing my sewer backup?
The diagnostic visit is $189, and we waive it if you go ahead with the repair. Home Protection Plan members pay nothing for it. Once we know what is wrong, you get a written upfront price before any work begins.
