Leaky clamp patch drain line (C) Daniel FriedmanDiagnose Clogged Drain vs Septic Blockage FAQs
Blocked Drain Diagnosis

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Blocked drain or drain backup diagnosis FAQs:

Questions & answers on how to determine if a slow or blocked drain is caused by drain line blockage or caused by septic system failure.

This article series gives advice on how to diagnose and fix clogged or slow plumbing drains and how to recognize failures in a septic system.

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Slow drain diagnosis: pipes or septic system FAQs

Toilet plunger clearing a sink drain (C) Daniel FriedmanThese questions & answers about how to tell the difference between a clogged drain line and a blocked, clogged, or failed septic system, were posted originally at CLOGGED DRAIN vs SEPTIC PROBLEM - topic home.

On 2017-10-30 by (mod) - signs of a clogged drain


From your description this sounds like a clogged drain, I agree.

An inspection of the sewage levels in the septic tank and distribution box can confirm that by an absence of abnormally-high sewage or effluent levels at those locations.

Articles at this website describe HOW TO FIND the SEPTIC TANK and HOW TO FIND THE D-BOX if you need that help.

That's a reasonable place to start: hire a drain cleaning service who can also inspect the drain system for types and location(s) of blockages. Let me know what you're told.

On 2017-10-30 by paul

forgot to tell you that after inspecting the well and septic area on property i do not see any floodind or water or smell anything unusual

we moved into a 2 level home ,have had no problems for 6 months now we have 2 upstair full bathrooms and 1 half bath downstairs i have always had sewer in past years but 1 upstair b/r is working fine including toilet ,shower /and sink the other upsyairs toilet seems like there is a clog between that upstair and downstairs .

we replaced downstairs toilet and tank with a new one but we do not have much of a flush when we use a plunger we have backup in shower then we clean it and water goes down from shower so it seems there is a clog between upstairs b/r and this half b/r the septic was just cleaned and pumped 2yrs ago.

i am not sure to call plumber or septic

On 2017-10-10 by (mod) - A septic field can be saturated but still passing out effluent slowly enough that we don't immediately see a backup

Good question Anon. A septic field can be saturated but still passing out effluent slowly enough that we don't immediately see a backup in the building that it supports. But it's a safe bet that we're headed for a sewage backup - typically occurring when the system is loaded more heavily by having many occupants in the building or by wet weather that further floods the fields.

Standing water over the septic tank sounds like a problem in any case: local groundwater flooding the tank will flood the tank and drainfields even if it's not coming out of the building as sewage effluent. The septic system cannot work under that condition and there is also a risk of backup.

On 2017-10-09 by Anonymous

Anonymous from 3 hrs ago, sorrry my name is Kelly, I felt I should add and clarify a few things pertaining to my earlier post.

We had our septic tank pumped because water was standing in the area of the septic tank, the water however has been clear water and thete has been no foul sewer stinch, I said it had filled back up in 2 days,

well I'm assuming it has filled back up because the water started standing again in the same area as before, the water is clear though and does not smell, hope this is a little clearer! Thanks!

On 2017-10-09 by Anonymous

If your septic leach field lines are full wouldn't you have sewer back up in house, we aren't having any problems in the house but water standing on septic tank, had it drained and it filled up in two days, but water is clear on top of ground, does not smell like sewer and did not smell like sewer before we had it drained, could we have a water pipe leak , instead of sewer priblem??

On 2017-10-09 by (mod) - it's not normal to see water running continually in a drain line

No, Mike, it's not normal to see water running continually in a drain line. I suspect that a toilet is running somewhere. Try turning off water supply to the toilets then turning it back on one by one. (Another possibility is a partially-blocked drain line, or some other water usage source like a water softener).

On 2017-10-09 by Mike

We have a drain clean out and can see water running after a flush. We put in a wad of TP on all three toilets but can never see that just the that normal?

On 2017-09-26 by Princess

I have a well system, septic, I have 2 bathrooms, everything is draining just fine, except for the toilet in my master bedroom, could the septic be clogged if only one toilet won't flush? When flushed it just fills the bowl up with water, after some time it goes down bit won't flush completely

On 2017-08-20 by (mod) -

Cindy the article CLOGGED DRAIN vs SEPTIC PROBLEM is my best explanation of how to sort out your question. Was that too long, confusing, or just annoying? Your critique will help me make the information more useful and usable.

In short, if all drains clog with the same amount of wastewater flowing into them, then it's either a bad septic OR a clog in the house main drain.
If just some drains clog then the problem is probably closer to the clogging fixture.

On 2017-08-20 by Cindy

Slow drain in shower and toilet, is it septic system or just a clog

On 2017-08-05 by Christa

Sorry that last post was mine. Not sure why it posted as anonymous.

Yes I did remove both of the traps and cleaned them . I have also plunged both sinks. I purchased a snake from the local hardware as well and tried to snake it. I can get the snake completely through both. I'm at a loss for what could be causing this to happen.

On 2017-08-02 by (mod) - kitchen sink was clogged/ draining extremely slowly

The good news is that what you describe sounds like a local drain problem. That would not be a septic system issue - if the septic were the problem I'd expect all of the drains to slow or back up.

Unfortunately the baking soda powder, if it was too much, may have added to a solid blockage.

Have you tried using a plunger?

If the blockage is in the trap, removing and replacing the trap might be a solution.

Keep me posted.

On 2017-08-02 by Christa

My kitchen sink was clogged/ draining extreamly slow in the hoe we just moved into. The bathroom sink, toilet, and bathtub all drained fine. I put vinegar and baking soda in the kitchen drain to try to clear it.

The next day i tried to plunge the kitchen sink. Once I started to plunge the kitchen sink it backed up in the bathroom sink. Now both sinks are blocked and will not drain at all. However the toilet and bathtub are fine. The bathroom sink smells of sewage. (very disgusting) Could this be my septic needs needs emptied. I live in a mobile home.

On 2017-07-18 by (mod) - how to fibure out if the blockage is the drain or the septic tank


It sounds as if wet weather has flooded the septic tank or drainfield or both. If so, the bad news is that significant work is needed.

If all building drains are slow or clogged, or if waste is backing up into the building from the lowest plumbing fixture, you would suspect the sewer line is blocked or there is a failing or blocked onsite waste disposal system (septic system).

On 2017-07-18 by Donna

We been having a lot of rain the past few days. Today my mom did some laundry and later found stuff in her bathtub(looks like water backed up) we have a septic tank. I'm not sure if there is a pipe clogged or if from all the rain the septic is full of water.

Is there a way I can figure it out myself? Don't have hundreds of dollars to call someone please help thanks

On 2017-07-01 by (mod) - main drain is blocked downstream of the point at which both toilet and shower empty into the drain system


Most likely the main drain is blocked downstream of the point at which both toilet and shower empty into the drain system. Or if there is no blockage in the building drain itself then the blockage is at the septic tank or in failed septic fields. The article CLOGGED DRAIN vs SEPTIC PROBLEM helps sort out whether the problem is in the building drain or in the septic system.

On 2017-07-01 by Mike

What does it mean when you have a septic system when you flush the toilet and it backs up into the shower

On 2017-05-27 by Izzy

I realize this might be a stupid question, but I'm moving into a third-floor apartment in Maryland, and wondering if I should bother getting the optional Water and Sewage coverage in my renter's insurance.

It "covers damages to a Resident's possessions when water backs up from a sewer or sump pump.

This endorsement applies when there is an issue with the sewage line from the street that causes the sewage to flow back into the apartment. It does not cover flooding, seepage, etc."
Are backups just a problem for basement/ground floor apartments? Thanks.

On 2017-05-02 by Tabatha

My bath tubs and toilets are filling up with water but not sewage is this just a clog?

On 2017-04-19 by (mod) - time to use a sewer camera to inspect the drain line

It sounds to me as if the drain is blocked. Perhaps your plumber can use a sewer camera to find the blockage or damage.

On 2017-04-19 0 by Jon

House on slab septic tank pumped out. Problem is washing machine drains into bathtubs.only 1 vent for housI've had 2 plumbers check it out,they didn't know. I think it needs more vents.HELP PLEASE

On 2017-03-27 by (mod) - clearance requirements of drain or sewer lines to property lines

Not a system I know - in looking I found for Colorado.

and a number of other discussions of this type of wastewater treatment such as a more academic article.

You've clarified the drain line vs. property line question - thanks.

Blocking a sewage effluent outlet while continuing to run waste into just about any septic tank or treatment system can cause trouble ranging from backups into the building to pushing the floating scum layer into an outlet tee or over an outlet baffle; IF that is what happened at your system then solids could have been pushed into the line to the drainfield or into the drainfield itself.

I'd suggest opening the tank to inspect the inlet and outlet baffles for signs of recent overflow.

Do keep me posted - what you find will help others. To send photos of the system and its investigation you can find our email at the page top or bottom CONTACT link.

On 2017-03-27 by Jackie

Thanks Daniel it's a W.P.C. Type A unit with filter, media, distributor, pump, control equipment and baffles. It has been working beautifully since 1982 and since we brought the property in 2002 . We had it serviced last year and a new pump put in.

Our property was built by the people that owned next door and the deeds give rights for the discharge drain to run through their garden to the ditch at the bottom.

They have since sold the piece of land with the discharge drain to developers who are putting up two houses. They said they had to block off the drain and relocate it to the new run between the two new plots. I

was just wondering if blocking the drain for the time they needed to reconnect it to the new route has cause it to back up and damage our unit? It has always discharged clear water and now it's not. It seems to be flowing fine but not filtering properly.

I've been waiting for an engineer to ring back. Thank you for your help.

On 2017-03-27 by (mod) - builders next door did something to our septic or sewer line?

Jackie I'm not clear on what happened, what's damaged, what repairs are needed.

1. In most jurisdictions it would not be permitted for sewer lines from house to septic tank nor from tank to soakbed to be off of your own property (plot) so I'm confused about why a builder on an adjoining property would touch your system at all.

Certainly they ought not be driving equipment across your land as the risk is damaging or destroying the septic system

2. You need to find out exactly what was done as well as the current state of the system by direct inspection - I'm not very smart anyway but certainly I can't see your property from here at my lab.

From your comments it sounds as if you r septic system uses a pump - I don't know where the pump is, what its pumping, where it's pumping to: sewage grinder pump to an uphill septic tank? An aerobic system? or an effluent pump to an uphill drainfield?

There is also a possibility that the line relocation not only left damaged or leaky piping but piping not properly sloped to drain properly.

You need onsite expertise: and probably some digging, to see what happened to the system and its piping, starting at the septic tank.


On 2017-03-27 by Jackie

Hello the builders in the plot next door had to re-locate our discharge pipe to our septic tank. Since then the tank has been discharging dirty waste. The builders said the blocked the drain off whilst relocating.

Could they have damaged the pump or the circuit board if the tank had been allowed to back up into the chambers? Thanks

On 2017-01-28 by Greg

Basement toilet has been gurgling for about a week. We've recently had the septic emptied (within the last year) I've taken the toilet off and snaked what I believe to be all the way into the tank (6ft snake) with no problem so I don't suspect a clog. Do you think the septic could be full?

On 2017-01-23 by Mark

Septic tanks were pumped last week. Its been raining really hard for days and toilets wont flush for hours then will flush maybe couple times. The cleanout is full of water and i ran a snake to the tank .

On 2016-12-30 by (mod) - local drain blockage close to the toilet

Jeff, that sounds like a local drain blockage close to the toilet.

On 2016-12-30 by (mod) -


Ken Riddell said:
Various reason can be there for clogged drain lines. Cleaning out plumbing services will fix your clogged or damaged sewer and drain lines quickly. You may refer to some plumbing services company which provide drain cleaning in south jersey that will be helpful for your problem.

On 2016-12-29 by Jeff

Only one toilet in our house is not flushing. Black contents in toilet and in the basement right below the toilet, water is coming out of the pipes.

On 2016-06-04 by (mod) - blockage pretty far down the drain system

Sounds like a blockage pretty far down the drain system or at the septic tank itself; that can happen by a pipe blockage, D-box blockage, or septic tank backflow from a failed drainfield. Your onsite inspector will want to open and look into the septic tank and Distribution box

On 2016-06-04 by A sudden Clog that is effecting our 2 bathrooms!

I took a shower first. There was no problem. Then my husband gets in and the tub starts to fill and wont drain. We then discover our guest bathroom toilet and shower are clogged too. There was no slow draining, no noises, nothing.

We located the septic and opened it. The water barely trickles out to the septic after flushing the toilet. So we figure the clog is a main pipe leading to the septic. We used a hand snake (25ft). We snaked both showers and toilets. Still its clogged. Any suggetions? Why would it clog so suddenly?

On 2016-04-19 by (mod) - Pumping a septic tank will never fix a clogged line nor a sewage backup


Pumping a septic tank, while critical for preserving septic drainfield life, will never fix a clogged line nor a sewage backup; at most it gives a few days of relief (while the septic tank refills from normal use) if the problem was a clogged septic tank outlet or failed drainfield.

Snaking a sewer line does not always remove blockages, particularly if it's just partial. Then a big blob of toilet paper combined with a volume of wastewater used can cause a sewage backup.

If all drains are slow or if the backup occurs in the lowest part of the building, I suspect the blockage is in the building main drain.

Perhaps your plumber can run a camera to inspect the drainline.

On 2016-04-19 by Perplexed

My drains toilets and pipes have been snaked, the tank does not need emptied ( was told by our septic guy), but we have back up! What could be the problem? there has been recent renos done to the house, a bathroom and kitchen added.


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