Septic Backing Up After Heavy Rain? What to Do on Clay Soil

Why does a septic system back up after heavy rain?

A septic system backs up after heavy rain for one of two reasons: the ground it drains into is full, or rainwater is getting into the tanks. Often it is both at once.

A drainfield or drip field works by letting water soak into soil. After a storm, the soil pores are already packed with rainwater, so effluent has nowhere to go. It backs up the pipe toward the tank, and if the tank is full, toward the house.

The second path is sneakier. Tanks sit in a dug hole that was backfilled with looser material than the clay around it. Texas A&M AgriLife points out that this backfill collects water, and if the tanks are not watertight, that water gets in and can flush sewage through the treatment system and into the yard.^source

Why Blackland Prairie clay makes rain backups worse

Most of Kaufman County sits on Blackland Prairie clay, which takes water slowly and holds it. That is the whole reason about 98% of recent county permits are aerobic or surface irrigation systems instead of conventional drainfields: the clay usually will not accept enough water through trenches.^source

The same clay behaves like a bathtub around your tanks. Rain runs into the softer backfill around the tank, cannot soak into the clay walls of the hole, and sits there. Any gap in a riser seam, a cracked lid, or a loose inlet lets that water into the tank.^source

Clay also swells when wet and cracks when dry. A long hot summer followed by a big fall storm is a classic setup: cracks open around risers and pipes during the drought, then fill with runoff when the rain finally comes.^source

What it looks like on an aerobic system vs a conventional system

On an aerobic spray system, rain trouble usually shows up as a high water alarm before anything backs into the house. On an older conventional system with a gravity drainfield, it shows up as slow drains and gurgling toilets.

That difference matters. The aerobic system's alarm is an early warning with some reserve behind it. The conventional system has no alarm, so the first sign is often a tub that will not drain.

What to do during the storm

During heavy rain, your job is to put as little water into the system as possible and stay safe. The system will usually catch up once the rain stops.

• Cut water use to toilets and hand washing. No laundry, dishwasher, or long showers until the ground starts to dry.
• If the alarm sounds, press the silence switch on the panel. Do not turn off the alarm breaker.
• Stay off the spray area or drainfield. Walking and driving on saturated clay compacts it.^source
• If floodwater is rising over the tanks or the panel, AgriLife advises shutting off power to the system at the main circuit panel and stopping all water use.
• If you have floor drains or a low shower that ties into the septic system, plug them so water cannot back up through them.
• Keep kids and pets away from any water pooling over the tanks or field. It may not be just rain.

What to do after the rain stops

After the storm, give the system a day or two to recover before judging it, and ease back into normal water use. On a time-dosed aerobic system, the pump may need a full cycle or two to spray down the extra water.

Then walk the system and look for the things AgriLife tells owners to check for rainwater problems.

• Low spots or depressions over the tanks where rainwater can pond and soak in
• Riser lids that are cracked, loose, missing screws, or sitting below grade
• Grass over the tank or pipes that is much greener and thicker than the rest of the yard, which AgriLife says can mean broken tanks or piping
• Soil washed away from pipes, lids, or spray heads
• Gutters, downspouts, or driveway runoff pointed toward the tanks or spray area
• Whether the alarm clears within about a day of normal use, and whether the spray heads are back to running only overnight

How long does a septic system take to recover after heavy rain?

Most rain-related slowdowns clear within a few dry days once you cut water use. On heavy clay, a wet week in spring can stretch that longer, because the soil drains slowly and the next storm may arrive before it dries out.^source

EPA's flood guidance sets a simple test for conventional systems: do not use the system normally until the water in the soil absorption field is lower than the water level around the house. If the field is still the wettest part of the yard days after everything else has dried, the soil is not the only problem.

A useful rule of thumb: temporary saturation gets better every dry day. A failing field or a leaking tank does not. It stays the same, or comes back with the next rain every time.

When a rain backup is a real failure, not the weather

Rain gets blamed for a lot of problems that were already there. Treat it as more than weather if any of these are true.

Common rain-related fixes and what they cost

Most rain-related repairs are small compared with a new system. The trick is fixing the entry point instead of paying to pump the same rainwater out after every storm.

Resealing or replacing a riser or lid is often done as an emergency repair. Texas lets the licensed person start those before a permit, as long as they notify the permitting authority in writing within 72 hours (30 TAC 285.35). Our article on the 72-hour emergency repair rule explains that paperwork.^source

How to keep rain from backing up your septic system

You cannot change the clay, but you can keep extra water away from the system. AgriLife's first recommendation is to divert runoff from roofs, driveways, and other hard surfaces away from the treatment and dispersal area.^source

• Point downspouts away from the tanks and spray area, or extend them past it
• Keep the soil over tanks mounded slightly so water runs off instead of pooling
• Ask your provider on every four-month visit to check riser seals and lids
• Spread laundry across the week, and skip it entirely during wet spells
• Fix running toilets fast; EPA WaterSense suggests a food coloring test in the tank to find silent leaks
• Do not park, drive, or run heavy equipment on the field, especially when it is wet (see roots, ruts, and rig traffic damage)

Who to call in Kaufman County

Start with the maintenance provider on your aerobic contract. Kaufman County requires every aerobic system to be maintained by a licensed provider, and your provider inspects every four months, so they may already know whether your tanks take on water.^source

If you do not have a provider, or you have a conventional system, you still need a licensed technician for any repair. You can request septic tank repair in Kaufman County and describe the storm, the alarm or backup, and when it started.^source

If the alarm is what brought you here, our first-response guide to a septic alarm going off covers silencing it, reserve capacity, and what to check in the first ten minutes. If the ground over the field stays wet long after the storm, read standing water over the spray field or drain field.