Sewage Backup After Rain or Heavy Use
A sewage backup usually shows up first at the lowest drain in the house: a basement floor drain, a shower or a toilet. It might follow a week of rain or a day of laundry and guests. Either way, it's a sign the system can't take water as fast as you're sending it.
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Warning Signs
The DHSS onsite system owner's manual lists the most obvious signs of trouble:
- Surfacing sewage, pooling water or muddy soil around the tank or field, or in the basement
- Plumbing or septic tank backups
- Slow drains and gurgling sounds in the plumbing
- Sewage odors in the house or yard
- Unusually lush green grass over the field
Safety First
- Keep children and pets away from backed-up drains, wet areas and any lagoon.
- Don't drive or park on the field. Vehicles compact soil and crush pipes.
- Don't open or enter the tank. DHSS warns that tank gases can be fatal.
- Wash your hands after any contact with sewage-soaked items.
Three Common Causes
The troubleshooting table in the DHSS onsite system owner's manual lists, for wastewater backing up into the house, a plugged sewer vent, or a tank that's backed up because of a clogged effluent screen, lateral lines backing up into the tank, or a tank that needs pumping. It also lists excessive water use and blocked plumbing. In plain terms:
- A full tank. Pumping brings the level down and often stops the backup.
- A blocked line between the house and the tank. Pumping won't help if the tank isn't the problem.
- A saturated field that can't accept water. The tank can be pumped, but it will refill if the field stays wet.
DHSS advises noting whether the problem came on gradually or suddenly and whether it's tied to weather, laundry or more people in the house. That pattern helps whoever looks at it.
Why Boone County Systems Back Up After Rain
Boone County's claypan and till soils are the main reason. NRCS rates the county's most extensive soils, Keswick, Mexico and Leonard, "very limited" for absorption fields because of a shallow saturated zone and slow water movement. After a long wet stretch, water perches on the clay and the field can't take much more. If you have a lagoon, the DHSS manual says any overflow must be kept out of natural drainage ditches and dispersed into the soils on your property.
What to Do Now
- Stop non-essential water use until the level comes down.
- Spread laundry over the week once things are working.
- Keep roof drains and surface water away from the tank and field.
- If sewage is in the house, see emergency septic pumping and say it's an emergency in your request.
If the cause turns out to be the field or the line rather than the tank, that's work beyond pumping. If the fix involves a major modification or repair, the DHSS manual says to make that contact before work starts. Around here, that means the county onsite program.
Related: septic tank pumping, septic inspection, septic pumping cost.
Request service with our short form
We pass your request to independent local septic professionals, and a local septic pro will contact you directly. They'll reach out as soon as they can; timing depends on their schedule. If it's an emergency, say so in the form so the contractor sees it.
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