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Toilet Doesn't Fully Empty When Flushed

Sometimes when I flush the toilet, everything doesn't go down. Sometimes the toilet just fills with water and NOTHING goes down!  What causes this to happen?

This can be one of the most frustrating and potentially expensive problems in plumbing. There are a number of things that can interfere with a righteous flush. They are (in no particular order):

Water level in the toilet tank is set too low...

A lot of people lower the level in the toilet tank to save water by adjusting the inlet valve float so that the valve turns off sooner. Yes, it does save water, but a lower water level means less power to move all the doo-doo from the bowl. Sometimes, the doo-doo has to make a long trip to the septic tank or public sewer.

A higher water level in the tank means more pressure and force when the valve is opened, so water drains quickly from the tank to the bowl, carrying the waste away. Lower water levels means less pressure which means water filters more slowly into the bowl and sometimes the job just doesn't get done. You're not saving any water if you need multiple flushes!

There are other things that can be done to save water and still get a good flush.

  • Put a stone, a brick, or even a water-filled plastic soda bottle in the tank. The object displaces water, so when the tank fills, the water level is the same, but less water is used. Because the level stays the same, the force with which the water drives into the toilet also stays nearly the same, just for a shorter length of time. Just take care not obstruct any of the toilet's moving parts!
  • Install water dams in the tank. They are flat pieces of flexible plastic-covered spring steel that are installed in the tank on one or both sides of the overflow tube/flapper assembly. When you flush, the water level drops quickly, but the water behind the dams is held back. You get the right combination of force and saved water.

Venting problems...

In order for any of your plumbing drains to work properly, a source of air must be allowed to enter the drain system behind the water flowing through the pipes.   If air is not easily available, a vacuum forms behind the water and slows it down.  This air is supplied by the venting system... an arrangement of pipes that connect all the drains in your home to a source of fresh air.  You may not even be aware of this system's existence, since the pipes are normally concealed within the walls... except for a small pipe that projects through the roof.  These vents are specially sized, located and sloped so that no waste water drains through them and so they allow adequate air for your plumbing system.

If additional fixtures are added to your plumbing system, such as in a basement bathroom, these must be connected to your existing vent system or must be supplied with their own vents.  Mechanical vents can be used  to save the expense of through-the-roof venting and the possibly difficult pipe installation.  However, these devices must be approved by your local plumbing code.

Back to toilets... because a toilet moves such a large quantity of water, a lot of air is needed.  Without this air from the vent, the flush "stalls" and the bowl does not drain fully... not the most pleasant sight!!

If the vent is blocked, the vacuum formed behind the large "bolus" of waste water tries to get air elsewhere.  The force can be strong enough to pull water from toilets and sink traps as it flows down towards the sewer.  Because the standing water in a sink trap keeps sewer gas from entering your home, this is a serious situation!

If you think you have such a blockage, it can be tricky to clear.  Some plumbers use a garden hose, and insert it into the roof vent, working it down into the vent gradually to wash out the blockage.  Since drain pipes enlarge as you move towards the sewer, a blockage on top (such as a birds nest) will not block the system further along.  Of course, if you see the blockage close to the top of the vent, it is wiser to try to remove it from the top!

I heard a story from a friend in a plumbing parts department about a plumber that did what I have just described.  He was working alone, and, as he twisted and turned the hose,  didn't realize that the hose had turned into a toilet drain pipe, goosed it's way through the toilet flange, into the toilet, and into a bathroom, flooding the bathroom.  So the lesson here is to have an observer...  just in case!

If you find that the birdies are nesting in your vent, or other creatures or debris fall into it, put a piece of galvanized screen oven the vent to prevent a reoccurrence.  Many birds, like campers,  love to come back to the same place every year!

Blockage in the toilet, floor flange or drain...

Sometimes, it takes nothing more than quickly pouring a few gallons of water down the toilet to loosen and wash away a blockage.  First, wait until the level in the bowl has dropped to below half full, or drain it out manually (Yecch).  Then fill a 3 to 5 gallon bucket with water and quickly pour the contents into the toilet bowl.  If the water seems to flow free, try flushing with an empty bowl first.  If this works, try a flush with a wad of toilet paper... you know, the "usual" amount!  If this works, you probably have solved the problem.  If not, more drastic action is needed!

A plunger will often free up simple blockages that occur with the toilet in "the bend" or at the floor flange. Using a plunger is easy, though sloppy!  If the toilet is full, you may need to bucket out a little water to limit splashing. Seat the plunger into the drain hole in the toilet bowl and pump it up and down a dozen or so times. The water hopefully will drain from the bowl. DON'T FLUSH YET!! First, get a 5 gallon bucket, fill it with water and pour it quickly into the toilet bowl. This way, you have some control over the water flow.  If the blockage remains, you won't flood the floor (again?). The added benefit of this high volume flushing is that the force helps to clear the blockage more thoroughly.  If the drain flows freely, pour an additional three or four buckets of water through the toilet... necessary overkill!!  Only then can you attempt to flush!

Unfortunately, even this may bring false hope.  Some types of small blockages may let water flow by and may appear to yield to the plunger.  Then the toilet will reclog when other "stuff" such as toilet paper pass by.  If this is the case,  you can try to use a toilet snake.  This is a special wound-wire apparatus that is inserted into the toilet bowl and through the drain hole at the bottom.  These special snakes have a rubber cover to protect the porcelain from scratching.  Be careful anyway!  Once the end of the snake in inserted into the drain, rotate the snake as you push it into the drain.  You may need to pull it in and out to get it to follow the internal bends of the toilet.  Once you have pushed about 4 feet of snake into the drain, withdraw it and pour a few gallons of water into the toilet bowl to see if the flow is improved.

If this method does not work, the next step is to remove the toilet from its base.  Don't rush this step... most drain blockages are not total, but you should wait at least a few minutes for water to drain below the floor flange, or you will have a flood!  You are looking for 1) small items that are stuck in the bends of the toilet, 2) an overly wide wax seal under the toilet (which can slow down the flow enough to prevent proper flushing), or 3) something stuck at the top of the floor flange.  I have things as varied as pencils and nightlights stuck in toilets, as well as clogs of burnt matches!  Junior... how many times have I told you not to play with matches?

If blockage is not visible, you may need to use a plumbing snake to clear the lines.  Depending on the extent of the blockage, this may require a pro or rental of heavy-duty snaking equipment!

Full septic tank...

A rule of thumb for septic systems: if you don't remember the last time you had it pumped out, make the appointment immediately!! If you allow a septic tank to overfill with solids, the result can not only be blockages into your home plumbing drains, but also the movement of solids into your underground septic system fields. The fields are where the overflowing water from your septic tank is absorbed into the earth.  The small amount of solid waste normally in this waste water is easily digested by bacteria in the fields.

In the case of a solid waste overflow, the large volume of solids can overwhelm the bacteria and cause the earth around the fields to become less porous.  The waste water will then accumulate near the surface of the ground, making it both marshy, smelly and a health hazard!  This is not a laughing matter... restoring septic fields can cost $10000 or more dollars!  And if the septic code in your area has changed since the original installation, you may be forced to spend five to ten times that to bring your system into compliance with the new standards... nothing to sneeze at!!

Blocked toilet bowl inlet holes... or the large inlet hole near the bottom of the bowl!

In many toilets, the water entering the tank when flushed comes through small, angled pinholes around the underside of the seat rim. The water rushes through these angled holes at high speed, causing the water in the bowl to swirl and the water level to rise. Any blockage in these holes will decrease water flow and movement, resulting in a poor or incomplete flush. These holes can be cleared by using an unbent paperclip or safety pin. Simply push the device-of-choice in and out of the holes to ream out any blockage.

There is a second entry point of tank water into the bowl at the front bottom of the bowl.  Though it is unusual for this large port of be blocked, it should nevertheless be checked.  One time I found a large brass nut in the hole!!  It was dropped by a plumber or do-it-yourselfer into the flapper drain, swam around the rim of the toilet and into the bottom outlet.  I was able to remove it after a little drilling and a little cursing!

The toilet drain pipe does not have a proper downslope...

It is imperative that drain pipes not be level! Based on the applicable building code, all drain pipe must have a minimum slope, generally expressed in inches per foot of run (such as 1" of rise for every 10' of pipe run, or length. Sometimes, because of settlement in the home, pipes that may have at one time had a sufficient or barely sufficient slope no longer do. When this happens, water pools in the pipe. When you flush, the large mass you are trying to get rid of runs smack dab into the sitting water. The collision stalls the flush, leaving a present for you in the bottom of your bowl. Happy Birthday!!

The solution (unpalatable as it may be) is to restore a slope to the pipes! How this can be done (and the expense involved) depends of how exposed the pipes are:

If they are in a basement with an unfinished or drop ceiling, go buy a Lotto ticket, 'cause you just got really lucky!

  • Perforated metal tape Put a level on the pipes to see whether they slope downward towards the sewer or septic system. If they are level or have a negative slope (slope in the wrong direction), check all pipe supports. If the supports have broken or stretched, lift the pipes into the proper position, and use perforated metal plumbers tape to hold them in place. Always use screws for this, in case you need to "fine tune" your adjustments!

If the drain pipes are concealed, they will have to be exposed before there can be any thought of repair.

  • If the pipes are within a concrete slab, grab the two jacks... the jackhammer and the Jack Daniels! Taking up a concrete floor is beyond the instructional mandate of this site.
  • If they are between a finished ceiling and floor, this won't be fun, either. You will need to determine where the pipes are, then cut out the plaster, drywall, etc., before proceeding to adjust them.

However you decide to proceed, be sure you have exhausted all other possibilities concerning pipe blockages, overfull septic tanks, etc., before taking a wrecking ball to your home. Please.

Or... don't do it yourself and relinquish this duty to your neighborhood friendly plumber!!

Return to Toilet Question List

Jerry Alonzy, the founder of Naturalhandyman.com

Written by Jerry Alonzy

Jerry Alonzy, a.k.a. the Natural Handyman, has been an active handyman for over 30 years with experience in most areas of home repair and renovation.

As a do-it-yourself author and web developer since 1995, he has been featured in USA Today, the Today Show and on radio shows, magazines, newspapers and websites. His material appears widely on the web, but primarily on his website... The Natural Handyman. You can also find him on Google+.