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Q&A on Clogged or Slow Drain Repairs

  • CLOGGED DRAIN DIAGNOSTIC FAQs - home - CONTENTS: how to diagnose and fix blocked or clogged plumbing drains. What signs indicate a clogged drain? How do we distinguish between a clogged drain and plumbing vent troubles. What are the steps in fixing a clogged drain?
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Questions & answers about how to fix a blocked or clogged drain:

Here are answers to frequent questions about how to diagnose and fix a slow plumbing drain or a drain line that is clogged or that backs-up.

This article series explains how to troubleshoot & repair slow or blocked plumbing drains, diagnose & fix sewer line or septic system backups & how to distinguish between a probable septic system failure versus a probable blocked building drain or sewer line.

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Clogged Drain Diagnosis & Repair: how to fix slow or clogged plumbing drains

Roof inspection of plumbing vent (C) Daniel Friedman

Recent questions & answers about diagnosis & repair of clogged or slow plum bing drains, posted originally at CLOGGED DRAIN DIAGNOSIS & REPAIR

On 2017-04-26 by (mod) re: what to check when adding water to the toilet tank still doesn't provide an adequate flush


If there's plenty of water in a toilet tank that doesn't necessarily mean that enough water is participating in the actual toilet flush - something you can check at least subjectively by watching the bowl when the toilet is flushed. Sometimes we have to adjust the lift chain on the flush valve flapper to give a bigger dose of water to the flush.

Second: clogs in the toilet rim water passage can also interfere with delivery of enough water in the right sweep pattern to flush well.

Third, I'd consider having the drain line inspected internally using a sewer line camera, looking for
- improper or inadequate slope
- a partial blockage
- a partial collapse or damage to the drain line

Keep me posted.
I'd also confirm that the drain lines are properly vented (do nearby fixtures gurgle when you flush the john?)

[Click to enlarge any image]

On 2017-04-26 by bob

We have two bathrooms in the home ( septic system ) One is approx. 16 ft. to discharge , the other is approx 28 ft. The 16 ft run works fine but the 28 ft run clogs when we use toilet tissue . There is no basement, only a 2.5 ft. crawl space .

We have had it inspected by a plumber and every thing seems to be o.k. They seem to think that there is not enough water flow ( 6 Lt. toilet ) to carry waste that distant (28 ft.) with that degree of slope. I have increased the water level to approx. 9 LT by playing with the float and over flow tube but we still have the problem .

On 2017-03-29 by (mod) re: pumped the septic tank because its level was "high"


A septic tank is normally ALWAYS full of sewage. But if as you describe the sludge level was too high then indeed solid waste would be pushed out of the tank and into whatever absorption system is in use ( a seepage pit or "dryrwell", or a soakbed or drainfield) where it clogs the soil.

In my OPINION use of acids as a septic soakbed "repair" is
- ineffective
- risks harming the environment by contaminating nearby water, wells, groundwater, lakes, streams
- is illegal in many jurisdictions


That is NOT to say that drain cleaners (including acidic products) used IN BUILDING DRAIN PIPING to try to clear a clogged trap or drain are
prohibited or ineffective - that's a different situation. Used as directed, and not to excess those products can be useful.

Some jurisdictions license septic installation and repair contractors, some don't. I've not come across a separate license for application of chemicals in septic systems.

For example using the U.S. state of Oregon, septic contractors must be licensed
Any person or firm engaged in the business of pumping septic tanks, holding tanks, grease traps, pit privies or
cesspools, or providing or cleaning chemical toilets must operate under permit from the Environmental Health
Division (EHD). Any non-permitted sewage pumping companies, vehicles, and/or non-certified drivers caught
operating in Contra Costa County may be subject to penalties, citations and/or other legal action.

On 2017-03-29 by Vicki Douglas

Septic tank and dry well were full and both had to be emptied. I was told level of sludge so high it went into dry well and beyond so they treated dry well with acid. Was this the right thing to do? Has the acid treatments damaged our drain field? Also do septic service companies have to have a separate license or certification for chemicals?

On 2017-03-29 17:32:29.506581 by (mod) re: toilet was slowly overflowing water over the bowl edge

Several possible causes:

1. a fill valve sticks and overfills the bowl - usually the bowl will self flush but on occasion I've seen tank overflows;

2. A drain line has developed a blockage - eg. by collapse, being driven-over

3. there is a community sewer system backup

4. There was other drainage into a system that caused a backup or failure such as roof, surface, or other runoff entering a basement floor drain or flooding a septic field

I'd start by having the main drain cleared and inspected by camera.

On 2017-03-29 by Marwan

The toilet was not overflowing when departing in the morning and appeared to be normal like every other day. When I came home from work, the toilet had been slowly overflowing water from the top all day long causing serious water damage.

What would cause this? Is this a plumbing issue or operator error, or a combination of blockage (plumbing) and malfunctioning toilet water flow system?

On 2016-12-21 by (mod) re: signs of a partly-clogged main drain pipe

Sounds like a partly-clogged main drain line.

On 2016-12-21 by lyle

commode sometimes flushes,then backs up . slowly drains then goes clear down into toilet then gurgles before backing up on next flush

On 2016-12-13 by (mod)

eny said:
Oh, thank you for that. I hope I will figure it out myself. Have some problems with drains and I need to fix it. My husband did that but he is in other city because of work. I'll try but think I will need to call service

On 2016-11-11 by (mod) re: Drain-FX drain de-clogger touted by Jack

Thanks for your opinion, Jack and for the report of your experience. Some drain de-cloggers can clean some types of clogs, such as a blob or blockage of grease or hair in the traps or in drain lines. Those products do not fix a failed septic system nor will they fix a blockage due to damaged or broken sewer pipes.

On 2016-11-11 by Jack

I have tried Drain-FX - heard about it on the Gary Sullivan show and bought it online. Cleared my slow running sinks & tub. I highly recommend it.

On 2016-10-14 by Andrea

Washing machine is in the basement. A pump pushes the water up 90• to the main drain. But the catch is that the wash water comes up into my kitchen sink. A vent has been put in place to help but it still goes on. What can be done.

On 2016-10-14 by Kathy

Kitchen sink clogged no other problems just kitchen. Used 50ft Snake... No response, still slow.. Help

On 2016-10-07 by Judy

Mound system in great shape. However, the pipe line has been compromised by sand coming in to the pumping station. Is there a safe

On 2016-09-07 by (mod) re: sag or belly in drain line causes clogs

If the line was inspected by a sewer camera the plumber's explanation could be spot-on.

Depending on the costs involved there may be other repair options including use of a horizontal boring machine to run a new waste line or converting the system to use a sewage ejector pump.

On 2016-09-07 by Barbara

My home us 30 years old. I recently experienced a sewage backup in the masterbath and called a plumber who cleared the blockage but said it would hapoen again since the sewage line buried in the ground under the concrete slab has shifted. He descibed it as having a belly.

He advised not flushing anything but water from toilet and drain from tub, shower, or sink. He said the repair is to tear up the floor in my house, dig through the concrete and dirt to replace that pirtion of the line. Does this sound right and any suggestions? Any advice is appreciated. Thanks

On 2016-06-19 by (mod) re: sink wouldn't drain, but the pipe seems clear for 12 feet

Indeed, Linda sometimes it's tough to get a manually-opearated drain snake past a simple elbow or bend in piping as well as getting it past an obstruction; I'd ask for help from a plumber using a power snake - or you can rent one but they're heavy to handle if working alone. An alternative is to have a fancier plumber who has one use a drain scoping camera to inspect the drain line for roots or collapse.

Keep me posted.

On 2016-06-19 by Linda

Sink wouldn't drain, no smell, no other blockage in house. Used a 12 foot snake, it got to a certain point and stopped but no debris on snake. Suspect tree roots? Small 8 foot tree close by. Only problem is with kitchen drain.

On 2016-06-09 by (mod) re: trying to use a snake to clear a toilet drain

Randy I've had bad luck using toilet snakes; if the blockage is close sometimes you can free it up using the plunger when the toilet is draining slowly and the bowl is full. Plunge for a half minute or longer as longer sometimes works.

If the slow drain is only at the toilet I suspect it's a either a close blockage or a problem that the bowl was not full enough at start of the flush cycle. If we're looking at a close blockage that we can't snake out through the toilet and can't free by plunging I'm afraid the next step is to pull the toilet from the floor entirely, then use a power snake or hand snake directly into the drain line.

On 2016-06-09 by Randy

When flushing toilet water rises then does not drain all the way I used a snake doesn't seem to help what's next

On 2016-03-05 by (mod) re: warning about flushing wet wipes down the toilet

David Stanley said:
More and more clogs are being caused by flushing Wet Wipes instead of Toilet Paper and they don't break down. Better solution is to get a Hand Bidet Sprayer and wash with water. Cleaner, greener, healthier and saves money....both before and after clogs!


On 2015-12-27 by (mod) re: shower water seeps out on floor by the toilet

Wade, that's odd indeed since a backup at the toilet base makes one suspect a blocked drain line;

The glub glub noise is characteristic of either a partly-blocked drain or a problem with the vent piping.

It's common for a shower drain to tee into (actually wye into) the larger drain near a toilet;

I'd try

1. running a snake thorough the shower drain
2. seeing if there is a relationhship between the amount of water run and the occurrence of the backup; for example if the backup is pretty far along the drain line, you can flush the toilet fine - it's filling the drain line and seeps past the blockage slowly with you never noticing the effect; but after showering for a time the drain fills up enough to back up at the toilet.

On 2015-12-27 by Wade

Hello, I have an odd plumbing faux pass. My home is a single story, built 5 years ago & connected to the county sewer/water system. When the shower runs in my bathroom, what appears to be the showers draining water begins seeping out of the floor, at the base of the toilet.

That toilet flushes fine without any problem. Another odd symptom is that while this shower anomaly is unfolding, the toilet in the other bathroom makes a glub glub noise. We just tried liquid plumber in the affected showers drain & it did not change a thing. Thank you in advance for your expertise....Wade

Question: how to clear a blocked bathtub drain

I am wondering how to clear a blocked bathtub drain. The bathtub has not been used for some time and it is blocked with solid buildup from minerals/calcium. I tried a few drain cleaners, scraping at it and boiling water to no avail and ended up bailing the water out. Any suggestions? - M. 1/15/2013


What is the drain piping material? I'm guessing galvanized iron or that + cast iron?

Are you connected to a public sewer or private septic?

Is this the only slow drain?

Is this bathroom over an occupied finished space or over an unfinished basement or crawl space?

How did you determine that the blockage is from mineral deposits?

The answers will assist in making some suggestions.

Reader Follow-up:

I believe it is cast iron piping.

It is connected to a public sewer system.

No, it's not the only slow drain - the bathroom sink is slow as well.

The bathtub is over an unfinished basement- M.


As the drain blockage you describe is just in a single bathroom and not throughout the building, I don't start by assuming it's a system drain problem; more likely a local drain issue; typically we find a combination of cast iron and galvanized iron; sometimes you can clear mineral deposits, even hair and other crud using an aggressive chemical drain cleaner; some plumbers also try using muriatic acid;

Watch out: The risks of using dangerous chemicals to try to open a blocked drain include at least these, in addition to those warnings on the product label:

The best procedure is to follow a series of escalating steps, starting with plunging, snaking if we think it's an actual clog from hair or a single point of debris, trying some drain cleaners (caustics & OTC cleaners dissolve hair, maybe paper, while acids such as muriatic used by a plumber can dissolve mineral deposits), with caution, and ultimately replacing the drain;

I have not had much success with trying to snake drains that are actually blocked by rust or mineral deposits; the crust of iron or minerals is just too hard to be cleared by pushing a wire through the drain, and even a rotary drain cleaner may have trouble attacking such deposits, though you could discuss that option with your plumber.

More often, if that's the problem, and if the chemical does not clear the blockage, at this step it's time to expose the drain lines and think about replacing them.

Detailed advice on proper diagnosis and cure for a clogged drain begins at our 12-steps in the article above,


and continues at


Finally, if you are right that mineral deposits from the water supply (unlikely with municipal water supply) are clogging drains, your building may need a water softener;


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