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Septic Problems After Heavy Rain or Snowmelt: What to Do, and What to Wait On

Updated

Most septic problems after heavy rain aren't a broken tank. They're waterlogged soil. Your drain field or mound can only take wastewater when the soil under it isn't already full of water, and a soaking rain or a fast spring melt fills it up. With nowhere to go, the water backs up toward the house. First the drains slow down. If it keeps raining, sewage can come up the basement floor drain. For today: use as little water as you can, stay off the soggy ground, and hold off on pumping until the field drains. If sewage is already coming into the house, call us at (920) 241-6573.

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Excavator bucket at work in a muddy lawn trench, with caution tape and orange cones around the dig

The Basics

Why Wet Ground Backs Up a Septic System

The real treatment happens in the soil under the drain field or mound, and it needs dry soil to work. That's why Wisconsin code requires the soil receiving effluent to sit at least 24 inches above the estimated highest groundwater and bedrock (SPS 383.44). When groundwater climbs into that zone, or rain soaks it from above, the field stops taking water.

Spring stacks snowmelt on top of rain. In 2014, after heavy snowmelt and a run of rainstorms, pumpers in northwestern Wisconsin told Wisconsin Public Radio that saturated ground had stopped drain fields from absorbing, so wastewater backed up into tanks and homes (WPR). Soil works the same way here.

Local Context

Lots Near Lake Winnebago and the Fox River

The U.S. Army Corps of Engineers regulates Lake Winnebago and the flow down the Fox, but a big melt can outrun that. In early April 2019 the lake sat about 1.5 feet above the level its regulation plan called for, with high flow expected on the lower Fox from Neenah and Menasha to Green Bay (Brillion News).

Low shoreline yards are where septic problems after heavy rain pile up. Wisconsin code requires a tank installed where the ground gets saturated to be set so it won't float (SPS 383.43), and that's one reason we're careful about pumping those tanks in a wet spring. Our pages on septic repair in Oshkosh and mound system repair in Neenah cover lake-country systems in more detail.

Safety First

What to Do Right Now

  1. If floodwater is over the tank or drain field, stop using the system. University of Minnesota Extension says a system covered by floodwater shouldn't be used (U of M Extension). The EPA's rule: don't use it until the water in the drain field is lower than the water level around the house (EPA, after the flood).
  2. If it's just soggy, cut water use hard. Hold the laundry, take short showers and flush less. Every gallon you skip is a gallon the field doesn't have to take.
  3. Stay off the field. The EPA says not to compact the soil over it by driving or running equipment on it.
  4. Watch the electrical. If you have a pump chamber and water reached the controls, have the connections checked before power goes back on (EPA).
  5. Keep away from sewage. If it's in the basement, keep kids and pets out. The EPA says to avoid contact because sewage "may contain harmful pathogens" (EPA, malfunctions). Don't open the tank yourself either. Tanks can hold dangerous gases.

Sewage in the house is an emergency. See emergency septic service or call (920) 241-6573.

Key Differences

Why We Won't Pump a Flooded Tank

Pumping is the first thing most people think of for septic problems after heavy rain. The toilets are backing up and the tank is full, so pump it, right? Not while the ground around it is saturated.

The EPA says not to pump during flooded or saturated drain field conditions, because an emptied tank can try to float out of the ground and may damage its inlet and outlet pipes (EPA). And with the field still under water, a pump-out buys you very little. We'd rather tell you to wait a few days than charge you for a pump-out that doesn't fix anything.

Once the field isn't saturated, the advice flips. The EPA says to pump the tank as soon as possible after the flood, and U of M Extension says the same once the water recedes.

Warning Signs

Wet Spot Over the Field: Rain or Failure?

A wet spot over the field is the most visible of the septic problems after heavy rain, and the hardest to read. The question is whether it's rainwater or wastewater. Walk it a few dry days after the rain stops.

Probably weather: the whole low part of the yard is wet, the water is clear, there's no smell, and it dries up as the rest of the yard does.

Probably the system: grey or black water, a sewage smell, or a spot that stays wet after the rest of the yard has dried. The EPA calls soft, wet soil around the drain field "especially when there have been no significant rainfall events" a good sign of failure (EPA).

Wastewater on the surface is more than unpleasant. "The discharge of sewage to the surface of the ground" is one of the conditions that make a system failing under Wisconsin law (Wis. Stat. 145.01(4m)). If your spot fits the second description, call us. Our septic repair page covers drain field trouble, and mound system repair covers mounds.

How It Works

After the Water Goes Down

Most septic problems after heavy rain ease off once the ground drains. Then:

  • Get the tank pumped. This is the pump-out that does some good. The EPA also warns that silt can settle in a flooded pump chamber and clog the drain field, so have the chamber checked too. Like any service, it's reported to the county within 30 days (SPS 383.55), and we file that report for you.
  • Get it looked at if anything seems off. The EPA recommends a professional inspection if you suspect damage.
  • Ease back in. Don't catch up on a week of laundry in one day. The EPA warns that doing it all at once can flood a drain field.

Prevention

Getting Ready for Next Spring

If the same soggy field shows up every April, something is sending water its way. The cheapest cure for septic problems after heavy rain is keeping that water off the system.

Move roof water. The EPA says to keep roof drains, sump pumps and other rainwater drainage away from the drain field (EPA, septic care).

Get the sump out of the septic line. Wisconsin's plumbing code is direct: "stormwater or clearwater piping may not connect to a sanitary drain system" (SPS 382.36(4)(b)1). University of Minnesota Extension gives homeowners the same advice: don't empty roof drains or sump pump water into the septic system; channel it away (U of M Extension). A sump or footing drain tied into the house drain sends groundwater into your tank every time it rains, right when the drain field can least take it.

Watch where the melt goes. Extension's advice is to watch the snowmelt and note where it pools and runs. If it runs across the field, talk to us before regrading anything near it.

If the field is under water every spring even after all that, the system may be too close to the water table for the soil it has. That's a repair or replacement conversation. For the other half of the year, see our guide to keeping a septic system from freezing.

FAQ

Rain and Snowmelt FAQ

Can heavy rain cause a septic backup?

Yes, and a backup is the most serious of the septic problems after heavy rain. Rain saturates the soil under the drain field or mound, the field stops taking water, and wastewater backs up into the tank and then the house.

Should I pump my septic tank after heavy rain?

Not while the drain field is still saturated. An emptied tank in wet ground can float and damage its pipes. Pump it as soon as you can once the field has drained.

Why is my drain field still wet days after the rain stopped?

If the rest of the yard has dried and that spot hasn't, or it smells, it's probably wastewater, which the EPA treats as a sign of failure. Call us.

Get In Touch

Septic problems after heavy rain won't wait for dry weather. Call now.

Call (920) 241-6573