Improperly flushing toilet (poorly flushing toilet)

[Note: More information and advice is available concerning improperly flushing toilets. Mike’s book ( provides details concerning this topic, details concerning the proper installation of toilets and other topics.]

Most people seem to know that an obstruction can cause a poor flush. Most people and many plumbers don’t realize that there are many factors that control the flush.

  • Obstruction and/or buildup
  • Proper water level in the tank
  • Proper water level in the toilet bowl
  • How quickly water flows from the tank to the bowl
  • Poorly designed and/or made toilet
  • Improperly installed toilet
  • Improper pipe work                                                 
  • Overloading toilets

An obstruction and/or buildup in the toilet bowl can cause a complete or partial blockage. A partial blockage is a poor flush. Usually this will soon be a complete blockage. An obstruction is usually from an object, an overload, or from gradual buildup. Sometimes the wax seal between the bowl and the floor flange can cause an obstruction.  Too much wax and/or misalignment can choke the flow.

The proper water level in the tank is controlled by the ballcock (AKA fill valve) being in proper working order and properly adjusted. Most toilets require that the water level in the tank be five-eighths of an inch to one inch lower than the top of the overflow pipe.


The proper water level in the toilet bowl can be determined by slowly pouring water into the bowl. Pour slowly and gently as pouring too quickly can cause the toilet to flush. When the water in the bowl gets high enough to begin draining down and out, it has reached the proper water level (the maximum before it begins to drain). After determining the proper water level, steps can be taken to insure the proper water level is maintained after each flush. The most common factors that cause problems with the water level in the toilet bowl are:

  • Amount of time the flush valve stays open. Most flush valves stay open long enough after the flush to help refill the bowl. The amount of time the flush valve stays open is different on various flush valves. Some toilets require that the flush valve stays open longer than others (some are adjustable). New toilets always come with the correct flush valve. Sometimes I find that someone has replaced the flush valve with an incorrect one. Sometimes I find that someone has replaced a part on a flush valve with an incorrect part (i.e., flapper). People don’t seem to realize that some parts work on the majority of flush valves, but some flush valves require special flappers or other parts. Proper flush-valve timing requires proper parts.
  • The amount of water the refill tube squirts down the overflow pipehelps refill the toilet bowl. If insufficient water is flowing from the refill tube, make sure it isn’t kinked. If that is not the problem, you will have to adjust, repair, or replace the ballcock.
  •  The water level in the toilet bowl before it is flushed is important. The proper water level must be maintained. For example, often people dump mop water into the toilet and lower the water level, or the water evaporates because the toilet is not used for a long period of time.


How quickly water flows from the tank to the bowl affects the quality of the flush. The most common cause of water flowing too slowly from the tank to the bowl is build up inside the toilet bowl flush holes (the small holes around the inside perimeter of the toilet bowl; also, most toilets have a large flush hole at the inside bottom). I use dental tools to clean the flush holes. If dental tools aren’t available, you can use a nail, small screwdriver, or a wire coat hanger. Be careful that you don’t accidentally mark the toilet bowl (marks are difficult to clean off). Often toilet bowl cleaning tablets placed inside the tank will cause reoccurring clogging of flush holes (the one I hate the most looks like blue jelly). The blue jelly type is very messy to remove, but if the complete tablet is not removed, you will have a reoccurring problem. I have had a few jobs where someone has dropped something down inside the flush valve (obstructing the flow to the bowl). I have picked out, and I have vacuumed parts out of toilets to correct this problem.


Poorly designed and/or made toilets usually require replacement. Some toilets are just not capable of a providing a good enough flush to suit the customer’s needs. Also, toilets are pottery, and sometimes they have defects.


 Improperly installed toilets might develop all sorts of problems. One of the most common problems is misalignment and/or too much wax. I can usually tell if I pull my snake back, and it is loaded with wax. If the problem is just too much wax, often I can clean it out with a special snake. I like a drop-head closet auger for this. If misalignment takes place with the type of wax seal that has a plastic funnel built in, I have to take up the toilet. Even if there is no misalignment problem, people seem to have more frequent stoppages when the funnel type wax seal is used because it seems that the funnel chokes the flow. Every good plumber I ever asked recommends cutting the funnel off. This funnel creates unnecessary back pressure and can create leaks and other problems.


It is rare that improper pipe work causes a poor flush. Some toilets are sensitive to the pressure and flow of incoming water. Certainly clogged or defective waste pipe can also cause problems.


Overloading toilets with too much toilet paper or anything else can create a problem. There is a dramatic difference between various toilets as to the load limits before they stop up and/or begin accumulating build up. Often people need to experience a toilet stoppage before they can determine what they can and cannot get away with. Sometimes I have to tell people to “do half your business, flush the toilet and then finish your business.” (Sorry, but I had to say it.)

Properly Installed Toilet

Details Are Important

There are different ways to approach any job. Carefully locate an honest, qualified professional or learn enough about the job to either do it yourself or supervise an unqualified person doing it (if local code and restrictions allow these options).  One of the most common major mistakes I find is people failing to understand how important details are.  People fail to do proper research and assume that they can save money by letting an unqualified person (i.e., a tile man, a carpenter, or handyman) install a toilet, sink, or other plumbing fixture. Sooner or later this gambling usually results in major, unhealthy problems that are very costly.

I strongly recommend that you find a properly licensed and insured, trustworthy plumber to do all of your plumbing work. If your local regulators allow you to install a toilet and you are determined to do it, please take the time to learn important details. In my book ( I provide plenty of important details concerning the proper installation of a toilet.