Septic Tank Back-Flooding FAQs

Q&A on how to diagnose & fix septic tanks with abnornal sewage levels
Septic tank backflooding (filling with water) due to leaks, groundwater, rain
Septic tank backflooding due to failed drainfield

Septic Tank Floods In Wet Rainy Weather FAQS

Tip: Also see SEPTIC TANK BACK FLOODING

Our septic tank fails when it rains: toilets won't flush and there's a septic odor indoors

We have a septic tank that is fairly new but every time it rains, no matter how lightly, our toilet won't flush correctly and when it rains all day we have the septic odor in our house but not outside and the toilet fills to the rim when you try to flush it. (Mar 16, 2014) debbie

Reply: see our explanation of septic tank back-flooding

Debbie it's a troubling question - it sounds as if rain runoff, perhaps from groundwater, surface runoff, or roof runoff is entering and flooding the septic tank, or worse, the drainfield. Even if the tank is new a failed older drainfield couild be at fault;

I'd ask your septic contractor to excavate and open the septic tank access ports to see if the tank level is flooding from surface runoff; And if you pump the tank and water runs back into the tank from the drainfield that'd diagnose a flooded drainfield. Either can back up into the house.

If the problem is really controlling surface runoff then you'll fix it by directing water away from the tank and drainfield.

See SEPTIC TANK BACK FLOODING or for drainfield flooding to read details.

When it rains water from the septic lines runs back into the septic tank, flooding it

I have flat ground. When it rains for days the ground get socked and the water from the lines runs back into the tank. Is there anything that can be done?
Bud4auburn@yahoo.com On 2018-02-28 by Buddy Cromer

Reply by (mod) -

Buddy

I am genuinely sorry to be the bearer of bad and expensive news, but a septic drainfield that floods from ground-water in a level area is probably improperly designed and needs significant revision.

The bottom of the drainfield trenches needs to be at least 24 inches above the seasonal high water table - that can mean a raised bed septic or mound septic design (search InspectApedia.com for those phrases to read details).

Sometimes an intercept drain around the fields can carry off ground-water and leave fields working but that works best where there is some slope and some hope.

I'm doubtful that it'd work in an entirely level area as water may just come up under the intercept drain and into the septic area.

When rain floods our septic drainfield we can't flush toilets and the tank floods; can we change to an effluent sprayer system?

We have a septic tank system with a drain field. In times when the ground is saturated and there is too much rain, the drain field water goes back into the septic tank and will not allow us to flush our toilets. Forget washing clothes.

I wondered if we could rely on a septic effluent sprayer system that would not back up. I also wanted to know if the system could be attached to the septic tank and replace the drain field permanently. On 2011-10-03 by Mary

Answer by (mod) - not without more changes to your septic system design

Mary, effluent dispersal by spray is used to dispose of effluent produced by aerobic or other wastewater treatment systems that perform a very high level of treatment inside the septic tank before the effluent leaves the system.

But I doubt you'd obtain permission to spray septic effluent from a system that was designed to work with a drainfield because you'd be spraying into the air and onto the ground surface effluent that was not sufficiently treated.

In a septic tank and drainfield system the tank performs just about 40% of the treatment, the remaining 60% being accomplished in the soil. By contrast, an aerobic system may perform up to 95% of the effluent treatment before it's released to a surface spray system.

When the ground is saturated our septic tank floods and our toilets won't flush - can we just add an effluent sprayer?

We have a septic tank system with a drain field. In times when the ground is saturated and there is too much rain, the drain field water goes back into the septic tank and will not allow us to flush our toilets. Forget washing clothes.

I wondered if we could rely on a septic effluent sprayer system that would not back up. I also wanted to know if the system could be attached to the septic tank and replace the drain field permanently. On 2011-10-03 by Mary

by (mod) - effluent dispersal by spray is used to dispose of effluent produced by aerobic or other - wet soils still mean septic system failure

Mary, effluent dispersal by spray is used to dispose of effluent produced by aerobic or other wastewater treatment systems that perform a very high level of treatment inside the septic tank before the effluent leaves the system.

But I doubt you'd obtain permission to spray septic effluent from a system that was designed to work with a drainfield because you'd be spraying into the air and onto the ground surface effluent that was not sufficiently treated.

In a septic tank and drainfield system the tank performs just about 40% of the treatment, the remaining 60% being accomplished in the soil. By contrast, an aerobic system may perform up to 95% of the effluent treatment before it's released to a surface spray system.

Be sure to read the detailed diagnosis and repair advice

at SEPTIC DRAINFIELD REPAIR BY CORRECTING SURFACE WATER RUNOFF OR DRAINAGE - if the drainfield floods in wet weather

Septic failure after it rained cats and dogs - told not to pump the tank

Hi, I just had my septic tank pumped, and I failed to properly seal the lid, with a tarp then dirt. So I noticed a pool of water, and I saw more dollar signs in my future. But when I googled it, it said you must not pump out water from the tank as it will damage it.

I cannot ask my tenants to stop using water, as they are to used to wasting water with lots of laundry.

So I may be forced to pump it out if it will not damage the tank. I myself cut back severely no dish washing for a month, a rare shower twice a month, beginning to feel real ripe, and not much toilet flushing. And lastly if I do not pump it out how long on average would it take to drain into the leach fields, its 2500 gallons. Thank you.

Sorry forgot to mention; it rained cats and dogs, and that is how it filled up with California rain. Thanks again. On 2019-04-11 by ella seneres -

by (mod) - pumping the flooded septic tank won't fix it - we need a proper diagnosis

Ella

I think someone has given you confusing information. Pumping a conventional septic tank does not ruin it damage you can or harm it. However it doesn't need to be pumped over and over again. The pumping frequency is given in the septic tank pumping schedule article in this series and depends on the size of the tank and the Wastewater volume or number of bedrooms or number of building occupants.

However if surface water is leaking into your septic tank it will flood the tank and flood the drain fields and possibly ruin them. That's a question to have answered by your septic contractor.

Watch out: if a septic tank or cesspool is home-made out of stacked stone or concrete block, indeed it can collapse if it's pumped out. Such systems are unsafe; keep people away and have it inspected by an experienced septic system contractor.

How do I diagnose septic field issues in our new home - can't flush toilets if the soil is wet or in rainy weather

We recently started having septic/drain field issues. We have been on our property for 20 years and never had a problem. We have a new home there now with a new foundation.

When the ground is saturated due to rain or sprinklers we can't flush the toilets and the washing machine will back up into the tub.

The toilets gurgle as well. We had the tank pumped (second time in 5 months) and it lookes like there is another smaller tank between the house and main tank.

There is no access to this but we saw sludge coming from it. The water from the drain field was also pouring into the tank. And suggestions on how to diagnose this properly as I don't want to just throw money at it? On 2021-06-29 by jhaug76 -

by inspectapedia.com.moderator (mod) - recently started having septic/drain field issues

@jhaug76,

1. Your septic system is either blocked or in total failure; wet weather saturation makes the failure show up but it's there regardless: a septic system as to work in all kinds of weather not just the dry season.

2. Pumping the septic tank prolongs field life but will never fix a failed drainfield nor remove a blockage there.

Scope the lines.

Alarm keeps going off on new septic system every time it rains

We have a new septic system in a new house. Everytime there is a hard rain the interior alarm goes off followed shortly by the exterior alarm.

I have to manually pump to get the alarm light to go off but it sounds again 2-3 hours later for up to 24 hours after it stops raining. When this happens we basically stop using water in the house. Is it possible for that much ground water to leak in or infiltrate the tanks? On 2017-05-14 by fernbri

by (mod) - septic pumping chamber is being flooded, alarm keeps going off

Fern,

From what you describe, it sounds as if a septic pumping chamber is being flooded.

In a new septic system installation that suggests to me that something is wrong with the installation.

Groundwater or roof runoff need to be kept away from septic tanks and drain Fields precisely to avoid this problem.

So you need your septic contractor to open and inspect the septic tank and the distribution box for signs of flooding in wet weather.

If that's happening, the water source is going to need to be identified and kept away from the septic components.

If water is leaking directly into the septic tank but not the drainfield it may be possible to repair the problem with a combination of sealing the septic tank pipe connections and cover and redirecting surface runoff.

Let me know what you're told as what you learned will help her other readers.

by fernbri - contractor added risers but septic tank still floods

thanks for the quick response. Contractor will be getting an irate caller first thing Monday morning. First time it happened they put another layer of risers on the two tanks but clearly groundwater is working its way to the tanks.

Thinking of putting a swale in to divert the runoff water down and around the septic tanks. I will pump it down for 10 minutes in a few to hopefully last the night. Need some sleep after being up every 2 hours last night!

by (mod) - septic pumping chamber is being flooded.

F

Best if you can get the contractor on your side of this matter. Keep us posted. Daniel

After heavy rain bathroom & garden tub is overflowing onto the floor.

Will bypassing water conditioner help or do we just have to wait for things to dry up?

The past 2 nights our master bathroom & garden tub is overflowing onto the floor. The only thing that is different @ night is our water softener runs. The stool flushes normally during the day. We've had like 2.5" of rain the past week which is way above normal. Anybody know why this has started all of a sudden? On 2019-02-10 by skashon

by (mod) - waiting for the ground to dry after rain won't fix a failed, flooded septic system

SK

When the septic system has failed - from flooding combined with perhaps inadequate original design or soil clogging - waiting for the soil to dry out will, sadly, not fix the problem - it's going to recur until the field is re-built above the high water table.

But I agree that it makes sense to stop the water softener regen cycle - that adds more water to the septic tank and increases the chance of sewage backup into the buiding.

There is of course also the risk of scale clogged hot water pipes, tankless coil, water heater, etc. when the water softener is out of service for much time.

Septic Tank Flooded Again After it Was Pumped FAQs

Why is my septic backing up into the basement even though we had the tank pumped?

How can I fix septic issues all the sudden it’s backing up in my basement I had it pumped 13 months ago what do I do ? On 2018-11-23 by April Roberts

by (mod) - pumping the septic tank will never fix a failed septic system

April,

Unfortunately pumping the septic tank will never ever fix anything.

Pump in the tank protects the field and extends the drainfield life but it won't fix a blocked sewage or septic line or will they fix a clogged drain field.

So if your septic drainfield is blocked or saturated and thus no longer accepting effluent flowing out of the septic tank, OR if there is a blocked line between septic tank and the drainfield, then you can expect the septic system to back up again after the tank is pumped - it just takes a few days to a week for your normal household plumbing fixture use to re-fill the septic tank.

What you need is some on-site diagnosis. That might involve looking at the sewers levels in the septic tank and looking at the waste water level in the distribution box or D box.

Septic tank "Back-Flooded" and Overflowed; the Pumpers didn't do a great job

I had not clue I was being robbed and not only that, but oh the thought I have 40 years of sludge that should have been sucked out,

I just spend the last hour reading your site. First I am a photojournalist; and you write so well. I was laughing most the time, as you are funny.

Second I had no clue all these decades, and its worth repeating this for others as they may not be as diligent as myself in exploring your site.

The Septic tank service has to use a pole to stir up the sludge so it can be pumped up.

That has NEVER happened, they just stick it in and look around. I had not clue I was being robbed and not only that, but oh the thought I have 40 years of sludge that should have been sucked out, my last septic sucker cost me 650 for 2000 gallons. He used a hose a little, but on one else ever did anything but suck.

I want to re re thank you for your site; its very informative and funny. From now on I almost feel I know more then these crooks because of your depth sharing and educating us.

Thanks for the learning curb on nothing I choose to learn about but had to. Bravo, oh and that you used s/he. Lord that almost made me weep. Hardly no one does that. Brava.

I am so sorry to bother you again. I am so relieved you are here. So I wrote before about the overflowing septic tank. It was backing up into my studio, the stench blablabla.

Had it pump, then snake thru the outdrain, and then did not cover manholes good enough, rained, flooded.

So no one could help me 4 months later! Finally one guy came up who put a measuring tape into a pipe that vents? the drain field, and said it was bone dry, and said if the septic tank is overflowing from the manholes but the leach fields are bone dry, possibly a clog.

I had someone finally come up today and I scrambled to come back and ask you, HELP. He ignored or did not want to hear about the dry fields and said pump the tank again and dig the leach fields.

I have no business owing a house, I inherited it, and I am on severe limited income, and to fork out 12,000 plus may put me under.

Now if I need it, I am gladly willing to bite my lip and pay up as I will pay for work rendered. But once again we come to those dry fields. And yes the system is 40 years old, but I never use nasty chemicals, I do not abuse water.

Thank you again for, us lost souls who do not know what is up and can easily be fooled and ripped off. On 2019-05-29 by ella seneres -

Reply by (mod) -

Ella,

My guess is that the tape down the vent opening finding no water could be a useful diagnostic if we were sure that the vet were actually near the end of one of the lines in the drain field.

I don't think that just pumping the tank again is going to fix anything, and it's not appropriate if the type of recently pumped anyway. I also don't think digging up the entire drain field is appropriate without more diagnosis.

You need a plumber on site who has a sewer camera and who can run that through the lines to find the distribution box and through the distribution box the drainfield lines that can then be examined directly.

Proper or best practices when pumping a septic tank

Yes, in addition to experience in the field and septic systems inspection, I've researched and written about the details of a thorough septic tank cleaning, as demonstrated to me by a Jimmy Herring, a Poughkeepsie septic pumping contractor.

And yes I agree that most pumpers are rushing the job.

There is no statute regulating what the pumping company must do - not in any jurisdiction I know-of.

About the claim that septic pumpers need to pump water back into the septic tank

In my OPINION the worst offense that you described is a septic pumping contractor not being thorough by failing to stir up the sludge on the tank bottom, and more: it's those people who get paid for "pumping" the septic tank, then they empty most of the pumped volume BACK into the septic tank, claiming that "the water is needed" which

1. Is Not true at all :

The water (septic effluent) is not needed and does not need to be pumped back into the septic tank; The septic tank fills up and begins treating sewage within a few days of normal use.

2. Misrepresents what they're doing and is likely to shorten the drainfield life:

Unless the return-effluent is very thoroughly-filtered to remove small fine floating solids, the septic pump chops up the sewage and disperses solids into the truck during pumping - putting that back into the tank clogs up the drainfield.

...

I'm indeed happy that you found our (as in editorial "we") information useful - we work hard on it and are grateful when a reader finds the effort useful.

I too am a photojournalist - card carrying member of the US Press Association - ok so I don't usually carry my card. I didn't know I was a journalist until a lawyer representing an electrical manufacturer told me so during a meeting with the US CPSC on aluminum wiring connectors.

The lawyer told some of the meeting attendees that he and his client would not continue the meeting with "that journalist" in the room.

I looked all around wondering if the NY Times had somebody hiding under the table.

Then he pointed at me.

I should have been upset, or insulated that he'd impugn my integrity but hell, the truth was I was really excited. Geez I told my friend as we took a break: After all these years, writing and scribbling since the 1950s, finally oh finally I'm a real journalist - I had no idea.

Followup by ella seneres - rain filled our septic tank back up

Sorry forgot to mention; it rained cats and dogs, and that is how it filled up with California rain. Thanks again.

Hi, I just had my septic tank pumped, and I failed to properly seal the lid, with a tarp then dirt. So I noticed a pool of water, and I saw more dollar signs in my future.

But when I googled it, it said you must not pump out water from the tank as it will damage it. I cannot ask my tenants to stop using water, as they are to used to wasting water with lots of laundry.

So I may be forced to pump it out if it will not damage the tank.

I myself cut back severely no dish washing for a month, a rare shower twice a month, beginning to feel real ripe, and not much toilet flushing. And lastly if I do not pump it out how long on average would it take to drain into the leach fields, its 2500 gallons. Thank you.

Answer by (mod) -

Elua

I think someone has given you confusing information. Pumping a conventional septic tank does not ruin it nor cause damage except by accident such as breaking a lid or cover or driving over the septic tank.

And when a tank is pumped out it should not need to be pumped over and over again right away.

The pumping frequency is given in the septic tank pumping schedule article in this series and depends on the size of the tank and the Wastewater volume or number of bedrooms or number of building occupants.

However if surface water is leaking into your septic tank it will flood the tank and flood the drain fields and possibly ruin them. That's a question to have answered by your septic contractor.

If that is happening see

SEPTIC TANK BACK FLOODING

Otherwise see

FLOODED SEPTIC SYSTEMS, REPAIR to read suggestions for repairing a flooding septic tank or soakbed system that floats full of water when it rains