My inlaws have one toilet in their house that regularly clogs. They have two more toilets that don't seem to clog at all. They live in a suburb with full plumbing (not a septic tank). The toilet isn't low-flow. They had a plumber come look at it, plumber says there's nothing wrong.

But every third time we visit, my husband clogs it. Or I do. Other guests seem to clog it, too. The residents don't clog it. My husband and I don't usually clog toilets. We do eat more meat, less fiber while visiting, but we travel tons and put up with drastic dietary changes and new plumbing all the time, and we don't clog toilets. Just this one.

What makes this one exceptional is that we often have to snake it when it does clog. Just plunging never releases the clog.

Is the plumber nuts? Is there something else going on here?

  • 4
    Did the plumber run a camera down the drain line, did he remove the toilet, did he go on the roof?
    – Tester101
    Commented Apr 9, 2012 at 15:00
  • 1
    No, no, and no. At least to my knowledge.
    – Amanda
    Commented Apr 9, 2012 at 15:02
  • 5
    Then tell you in-laws to get their money back; if the plumber didn't do any of these things then he can't have done anything that would diagnose the problem.
    – KeithS
    Commented Apr 9, 2012 at 17:24
  • The "good" toilets wouldn't happen to be on a second floor while the "problem" toilet on the first, would it? I'm thinking that the problem toilet's drain pipe may have shifted and lost the proper pitch...
    – ShoeMaker
    Commented May 1, 2012 at 4:40
  • @ShoeMaker, nope. One good on the first floor, on good on the second. Clogger is on the second.
    – Amanda
    Commented May 2, 2012 at 16:04

9 Answers 9


Troubleshooting steps/questions:

  • Has this toilet always had this problem, or was there ever anything installed in this location that didn't clog like this? If the toilet has always had this problem then it's likely some issue with the initial installation; the drain pipe diameter may be too small, or there may be insufficient venting which is causing slow drainage in the wall because there's no "air behind water".

  • If it didn't always have this problem, then something has changed. Would that be anything obvious like a remodel, or something more gradual like build-up accumulation? If the toilet was replaced at some point, either as its own job or as part of a larger remodel, then most likely something was done during construction/installation that is causing an obstruction. If not, then mineral or organic build-up is the most likely culprit.

  • From the comments, what DID the plumber do, if he didn't scope the drain, lift the throne, and/or inspect the vent stack from the roof? Anything he did do, besides flush a toilet with nothing but clean water in it, may help to eliminate or diagnose potential problems.

  • Does the toilet always seem to drain slowly, even if it doesn't clog outright? Slow drainage of the bowl in all circumstances would point to an obstruction of the pipe diameter itself, such as an improper flange installation, a defect in the toilet, or blockage in the piping. Fast flow in a "normal" flush, but easy clogging, generally points to a foreign object blocking the pipe in such a way as to trap solids as they go down the drain, but allowing water without any solids to pass by normally.

  • Are there small children in the house? A child could have flushed a pencil, pen or other long, stiff object which is now caught in a turn in the plumbing and is trapping solid matter to form clogs. Scoping the drain will identify this blockage, and a professional snake will clear it (the homeowners'-variety snake with a coiled end won't do anything; you'll need a snake with bladed ends designed to chew into or through solid blockages, which require some knowhow to use without further damaging your drains).

  • Keith, everyone has grown now, but the toilet has been there for more than 20 years so once there were children. And ... my husband and I have only been together for ten years, but it's had the problem since I've known him. This is all good and helpful advice to pass on.
    – Amanda
    Commented Apr 10, 2012 at 16:29
  • We're headed back later this month so I'll have a chance to check in about all these tips.
    – Amanda
    Commented Jul 1, 2012 at 18:38
  • 1
    I'm accepting this answer for thoroughness. We still haven't figured it out. T
    – Amanda
    Commented Jul 22, 2014 at 14:13
  • The "no air behind water" part of the first bullet is a common misconception. The toilet bowl is open to the air, so the typical analogy of an upside-down soda bottle going glug-glug-glug is not applicable at all. A drain vent is there to prevent the trap being siphoned, and that's it. There are tons of information sources out there that have this flat wrong - a blocked vent won't slow your drain. Commented Aug 16, 2019 at 15:17

The first thing I would recommend is to use one of the other 2 toilets that don't clog. For the troublesome toilet, these are some clogging factors:

  • Too much waste. Try multiple flushes or cut down on the amount of paper. Switch to a different brand of paper.
  • A foreign object is in the toilet. Maybe a toothbrush or something that cannot be flushed is clogging the toilet line.
  • Clog in the vent pipe, the plumber should had checked for this but a vent pipe that is clogged will effect plumbing and flush capability.
  • Insufficient flush for the toilet design. Not all toilets flush equally, try replacing the toilet with one with a good flush. Toilets are pretty easy to replace. This may reveal other things as well like maybe the toilet is not seated properly (wax ring issue).

If there are no other clogging issues, then the problem is most likely localized to that one plumbing fixture, but if thre are other issues, then the problem may be further down the line which a plumber should be able to diagnose and fix.

  • You could swap the bad toilet with one of the good ones, checking for obstructions along the way. That will tell you a lot.
    – Jay Bazuzi
    Commented Apr 9, 2012 at 23:26
  • @Jon Raynor +1. He nailed my problem from a couple of years ago with this answer. Basically I had the same problem because we didn't use a toilet for days at a time and over the years we had the insufficient flush problem because the jets became clogged with calcium buildup. Changing the toilet fixed it.
    – lqlarry
    Commented Apr 10, 2012 at 0:34

I ran across one where someone had put a plastic cup down it, the bottom of the cup came out but the cup stayed creating a funnel restriction. Worked fine most of the time. The owner had tried all the plunger and snake variations he could.

  • Yes, objects can partially clog a toilet, such that snaking won't fix it but it still won't flush well.
    – Jay Bazuzi
    Commented Apr 9, 2012 at 23:25

Since all the obvious technical solutions have been provided and are excellent answers, however the obvious has been missed:

If this is a new toilet, check to see if it is "Eco-friendly". These new toilets have less water in the tank thus less force to push the waste down. If you are used to an older toilet, this could very well be the culprit - especially if a plumber was brought in and said there is nothing wrong.

You can confirm this by locating the make and model of this particular toilet and check the Flush Performance Rating

Home Depot Toilets Buying Guide

Flush Performance

A vital indicator of a quality toilet is the overall Flush Performance. A toilet with a higher flush performance will ensure that all waste is cleared within one single flush and mitigate the chance of clogging. Using Maximum Performance (MaP) scores you can be confident that the toilet will perform as expected, and remove the waste levels indicated. What you choose should suit your needs based on the grams of waste expelled by the typical user. From 350 to 1000 grams of waste per flush, the rating system will ensure the toilet you choose is right for you and your family.

I recently installed a new toilet and it began immediately apparent that we had to adjust the amount of TP we used in order to avoid clogs.


I had this embarrassing problem the plumber took the toilet out and thoroughly checked everything, the answer was hard water, it had formed into chunks like a grey cement, after removing all that and flushed it through he fitted a new dual flush as well, the other one the plastic had split. Now all is well the family and visitors are happy.


The truth is INSIDE THE PIPE! The shortest path to resolution on this is to send a camera down. Speculation on what MIGHT be wrong is a waste of time.

Having said that, I -will- toss in an anecdotal item not yet mentioned. We have a basement toilet that was easy to clog. As part of a previous remodeling, the owner (or contractor) added a wood-framed wall behind the toilet. This caused an alignment problem, "fixed" with a VERY short S-curve pipe right below the toilet.

I removed the wall framing, AND the s-curve, and have never been bothered again.


I had a similar problem with a toilet near a cat litter box. A member if the family had been flushing the clumping cat litter scattered by the cat into the toilet after sweeping it. Clumping car litters are clay based. Over time, the clay ha adhered to the walls of the serpentine in the toilet reducing the opening. Replacing the toilet and relocating the cat litter box fixed the problem.

  • 1
    Not the problem here, but this is definitely something worth checking if you're here because you have the same problem.
    – Amanda
    Commented Aug 19, 2015 at 16:52

Put two toilet roll cardboard centres, either side by side, or end to end, and if the modern 4.5/3 litre toilet cannot handle that, then the toilet, in my opinion, is useless. Bunnings and Masters plumbing salesmen say that this is a common problem with modern toilets with low flow rates. The throat of the toilet is so small that, even with increased water velocity, it will not clear. On nearly every occasion, I have to use up to ten 9 litre buckets of hot water to eventually clear it.(That is 90 litres, which is a little big more than 4.5 litres !) Before I get another toilet, I will get one with a 100mm throat, not 80mm.And it isn't just the throat cross section, it is the curvature or the throat. I got my money back from bunnings for my present Estilo, and will probably get another one in Masters closing down sale.


If you are happy with the toilet and it only happens for one person possibly a women, it may have to do with her possible pregnancy. Women take prenatal which seems to contribute to this plus the pregnancy itself could be a factor as well. I will see if things improve at my home but but this is the only suspect. I was otherwise very happy with my top rated toilet that I installed less than a year ago which has surprisingly clogged 3 times in last 2 weeks. The remedy in this case should be to flush mid way or multiple times during single visit.

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