TOILET FLUSHES POORLY - CONTENTS: How to diagnose & fix a slow-flushing toilet - poor flush toilet repair guide. How to diagnose and fix a clogged toilet drain. How to fix a toilet that is overflowing when flushed - in an emergency. How to diagnose and correct drain noises occurring when the toilet flushes. Slow toilet tank fill problems. Toilets that keep running - fill valve does not shut off the toilet tank fill valve? Toilet flush valve or flapper valve problems. Toilet tank fill valves and water sanitation. Sewer gas odors in buildings traced to loose or leaky toilet drains. How to repair problems causing plumbing drain sounds
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Slow flushing toilet repairs:
Here we explain how to diagnose and repair toilets that flush too slowly or have a weak flush, sometimes backing up.
We explain how to diagnose and repair problems with toilets, leaks, flushes, odors, noises, running and wasted water.
Our page top photo shows ugly staining in a toilet bowl - strong evidence that this toilet has been running, wasting water, possibly flooding the septic system, and sometimes giving bad flush performance as well. Details are below.
Toilet Flushes Poorly - Too Slowly, or Leaves Waste in the Bowl
There are several other reasons why a toilet fails to flush properly besides a clogged drain.
Here we list each cause of toilet flushing difficulties and suggest how to diagnose and repair the condition.
Poor-flushing low-water-consumption toilets: Keep in mind that modern low water consumption toilets (ASME/ANSI A112.19.M) are designed to use 1.6 gallons (6 liters) per flush or less - a desirable step in reducing water consumption in buildings.
But with the lower total flush volume designed into the toilet, if the toilet fill and flush valves are not properly adjusted, these toilets may cause complaints of poor performance. Don't rush to change out a toilet that is not working satisfactorily. toilet flush control tune-up may be all that's needed.
Our photo (above) shows the water level in a modern low-flush toilet tank, sitting just a fraction above the fill line. This toilet has adequate water to flush properly, if it is properly vented and if its drain is not blocked.
Vent defects: the plumbing vent may be partly blocked. If a gurgling sound
is heard at a sink or shower drain only when a nearby toilet is flushed,
or at a sink or shower when a nearby tub is draining, we'd suspect that the building drain-vent
system is inadequate.
The toilet may not be properly vented. If the trap at the nearby bathroom sink is an "S" trap (shown at PLUMBING DRAIN NOISE DIAGNOSIS), there is a good chance that no plumbing vent was ever provided and it's an older building.
Low-Pressure CIstern by Design: a low-profile toilet may be installed (photo at above-left). Some low profile toilets use a very low toilet tank for aesthetic reasons. We have found that some of these models do not flush well unless the cistern volume is perfectly adjusted, the drain is working perfectly, the vent system is perfect, and no challenging waste deposits are in the toilet bowl.
A poor flush factor may be the lower water pressure afforded by low profile tanks that are not as high above the toilet bowl. The author's mother swapped out all of the low-profile toilets in her home because of dissatisfaction with the toilet's flush performance.
Check & Adjust the Toilet Cistern or Tank Fill Volume
If the toilet flushes poorly, leaving waste in the bowl and if you are sure that the drain is not blocked and that the vent works, check the toilet cistern volume and toilet bowl volume.
The volume of water in the flush tank may be too small. When the toilet tank refills, notice where the water level is when the fill-up stops.
The level of water in the toilet tank should be within 1/4" of the "toilet tank fill line" marked inside the toilet tank.
At the highest possible toilet tank fill-up, the level of water will be just below the top of the toilet tank overflow tube in the center of the tank.
The rate of water running into the toilet tank may be too slow (some of this water slightly aids the flush), or
The starting volume of water in the toilet bowl may have been too small.
Check the diverter tube: Too little water in the toilet bowl to start with may be due to a lost or mis-connected fill tube that directs some water into the toilet tank standpipe (and thus into the bowl below), while the toilet tank is being re-filled. Check for that little tube.
Our photos below show the incorrect (below left) and correct (below right) connection of the toilet tank tube that sends some water into the toilet bowl while the toilet tank is filling. (These are two different toilets.)
Check the toilet cistern fill valve or float assembly adjustment: if the toilet cistern is not filling up to the indicated volume line in the toilet tank or cistern and if the diverter tube (above) is indeed properly filling the toilet bowl itself, you may need simply to adjust the position of the ball-cock float or the vertical rise distance of the toilet fill valve to put more water into the cistern.
For a toilet ball-cock float operated cistern fill valve, adjusting the float arm to raise the float will cause more water to fill the toilet tank or cistern.
For a vertical rising concentric float type fill valve (just visible at the left of our photo at above right) a sliding or screw-operated adjustment changes the position of the vertical float to increase (higher) or decrease (lower the float) the cistern fill volume.
Check also for clogged toilet bowl rim holes: hard water or debris passing into the bowl rim from the cistern or toilet tank can partly clog the rim holes designed to wash down the toilet bowl sides in most toilets. Clogged rim holes will slow the delivery of some of the toilet flush-water volume and can contribute to poor toilet flushing. Using a vinegar soak, lime or scale removers or even dishwasher detergent can help clean up a toilet bowl and clogged rim (along with a toothpick - Ed.)
At More Reading is a complete list of toilet trouble diagnosis and repair articles. Some toilet problems are fixed easily and right at the toilet by a simple adjustment, while others may not be the toilet's fault at all, and may need more thoughtful diagnosis and repair.
Lifting off the toilet tank top is often all you need to do to see how to fix a toilet flush problem.
Some of these simple toilet diagnosis steps require that you look into the toilet flush tank on the back of the toilet. Just lift the top off of the toilet tank and set it carefully aside on the floor where you won't break it or trip over it.
This article series TOILET REPAIR GUIDE discusses the cause, diagnosis, and repair of toilet problems (water closet problems) such as a toilet that does not flush well, clogged toilets, slow-filling toilets, running toilets, loose wobbly toilets, and odors at leaky toilets.
Continue reading at TOILET CLOGGED to diagnose and fix a blocked or clogged toilet or select a topic from the More Reading links shown below.
(Mar 1, 2014) Anonymous said:
Thank you for your clear concise and very helpful guide.
Thanks for taking the time to post your note, Anon; don't hesitate to ask if you can't find information you need, as that question helps us both. Daniel
Question: dishwashing detergent & increasing the cistern water level helped clear up a slow flushing toilet
(Sept 11, 2014) Anonymous said:
My poorly flushing toilet problem was solved with the dishwashing detergent tip; then increasing the water level in the tank should help keep things moving along.
This is one of the best "how to" sites I have used. Thank you
Thanks for the feedback Anon, it will assist other readers.
Question: bad smell out of drains when toilet is flushed
(Oct 15, 2014) Lisa said:
We just moved in the new built home and found out 3 toilets have same problems - weak flush and making a gurgling sound at the end. normally the problems will start from the a toilet in the powder room on the first floor then will affect the two toilets on the second floor at the next couple of days. The toilets are 1.6 Gal KOHLER. Any idea?
(Oct 16, 2014) lyndamae ooms said:
sometimes when i flush my toilet with the lid closed it flushes and a little bit of toilet paper comes back up out of the hole looking a little chewed up... the toilet seems to be noisier when flushing.. i recently replaced the toilet flush valve with a new one but did not notice anything right away.
i am wondering why this is happening? we never had a problem before..
also my house sunk about 1 and a half inches and it was raised again this summer... could something be broken inside all the plumbing inside the house or outside the house... the sewer pipe under the house going into the septic tank was severed from the house side.... and replaced with ABS sewer pipe to bring it up to code... it was about four inches from the house and four inches from the tank that was replaced. help i just don't know what to do.
(Jan 2, 2015) Anonymous said:
When the toilet is flushed, a really bad smell is coming out of every drain it seems. It is septic tank smell. I replaced the seal and it didn't help. The toilet does not flush completely and there is no smell when we use the sinks.
Anon noises or odors at nearby plumbing drains when a toilet is flushed often means that the plumbing vent system is blocked or incomplete.
Question: toilet flushes better when pour a bucket of hot tap water into it
(Jan 3, 2015) Anonymous said:
What makes a toilet flush fine when pouring a bucket of hot tap water in it, but when flushed normally it drains slowly. Even when using a plunger it won't go down but when hot water is poured in it goes down fine ad no waste is left behind. I have used an auger and even did the enzyme treatment and no change.
Probably the volume of flush water and the speed of its delivery into the toilet bowl is what makes the difference. I've seen this problem in some older homes that used an under-sized drain line or in drains that were partly blocked by corrosion or deposits. Check that the plumbing vent system is functional while you're debugging this issue.
Question: toilet flushes then sewage returns back into the bowl
(Jan 5, 2015) Peter said:
my toilet when flushed seems to flush away waste then later it all comes back into the bowl?
You might see this if we have a pair of toilet troubles:
The plumbing vent system blocked or incomplete
The main drain is blocked downstream from the toilet
With this pair of problems a flush can send a bolus of water and waste down the drain, compressing air in the drain piping; but as the compressed air and sewage meet a blockage the air pressure sends the waste back to the toilet.
How quickly does the waste return. If it's almost immediately I suspect that there is a blockage close to the toilet. If it recurs later I suspect there is a blockage more distant down the sewer piping or in a private septic system - if your building is connected to one.
Is this problem unique to just one toilet in the building?
On what floor is the toilet?
How far below does the waste line exit the building: one floor, several floors, etc. ?
Are there gurgling or other noises when plumbing fixtures are drained?
Does the backup occur later as a result of other fixtures being run and drained?
Don't forget to check other causes of a slow-flushing toilet, especially a clogged siphon jet (in the bottom, front of low flow toilets) or an obstruction in the vent pipe up on the roof. The four main causes of a slow flush are (Actually David listed five causes of slow toilet flush)
Not enough water in the toilet tank or cistern (not really - this doesn't cause a *slow* flush as much as an incomplete one - Ed)
Partly clogged drain (yes we discuss this above - ed)
Clogged rim holes around the toilet bowl (same effect as not enough water in the tank or cistern but you should indeed check for this - Ed.)
Clogged "siphon jet" (check in the toilet tank or cistern: if the small tube that sends water to the toilet bowl is not properly connected (sending water into the cistern or toilet tank instead) then the effect will show up as not enough water in the toilet bowl at the end of the tank or cistern fill cycle - Ed)
Clogged "air vent" (properly, this is a blocked, clogged, or missing plumbing vent, discussed in this article series - Ed.)
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Thanks to reader J.D. for discussing troubles getting a toilet to flush properly. The supposition that the toilet flushing problem was due to a defective toilet bowl, versus due to improper fill and flush control setup, was tested ad nauseam by this homeowner, her son, plumbers, and plumbing suppliers. 05/29/2010
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