5 Reasons Your Toilet Is Flushing Slowly | How To Fix It

Does a slow-flushing toilet have you scratching your head? There’s likely a simple reason for it and an even simpler solution. Let’s dive in and find out what causes a toilet to flush slowly and what you can do to fix it. 

5 Reasons Why Your Toilet Is Flushing Slowly

Your home contains many important systems that keep it comfortable and safe to live in. With that said, there’s none quite as vital as the septic system. Without a properly functioning toilet, a home can get very uncomfortable and dangerous rather quickly. 

So, when a toilet in your home seems to be flushing slowly or partially, it becomes a great concern as leftover waste in the bowl can be frustrating and even embarrassing when visitors stop by. The good news is that a slow-flushing toilet is usually easy to fix, especially if you’re an avid DIYer. 

Many homeowners ask, “Why is my toilet flushing slow?” In the information below, we’ll explore the five main reasons for this common problem, as well as some possible fixes. 

1. Insufficient Water Level In the Tank

Probably the most common reason a toilet flushes slowly is inadequate water flow into the bowl. If there isn’t enough water in the tank, there won’t be enough pressure to push the waste into the drain, thus leaving behind some of the waste to be flushed away with a second (or third) flush. 

This issue is easy to fix by adjusting the float that sits on top of the water in the tank. This float tells the toilet when the water level inside the tank has reached a sufficient level and the water stops filling. To increase the flushing power of your toilet, adjust the ball float so that more water fills the tank before the fill valve shuts off. 

2. Worn Flush Value Or Flapper

The flush valve assembly and flapper are located inside the toilet tank and are responsible for the flow of water into the bowl each time you flush your toilet. If these parts are worn or otherwise malfunctioning, it can restrict the water flow into the bowl and cause partial or slow flushing. 

Depending on the type of flushing mechanism your toilet has (flush valve or flapper), you will need to replace some or all the parts of the flush valve assembly if this is the reason your toilet is flushing slowly. Replacing these parts is relatively easy, but if you aren’t comfortable doing it yourself, don’t hesitate to call in a plumbing professional. 

3. Mineral Build Up Around Toilet Rim

Water flows from the tank to the bowl through jet holes located under the rim of the toilet. These holes are rather small, making them susceptible to mineral buildup over time. This is especially true if you have hard water that contains excess calcium and/or magnesium. If your toilet is a few years old and you have hard water, this could be why it is flushing slower than it used to. 

To restore your toilet’s flushing power, spray white vinegar around the rim of the bowl and use a stiff-bristled toilet brush to remove the mineral buildup. You may even want to consider installing a water softener in your home to keep this issue from happening again in the future. Not only will it keep your toilet functioning properly, but a water softener will also protect and extend the life of all your other appliances that use water. 

4. Obstructed Drain Vent

Many people don’t know that the wastewater removal system in their homes is dependent on drain vents to flow freely. These vents are usually located on the roof, and they carry away foul smells and noxious gasses so they don’t build up inside the home. They also allow air to enter the pipes so that water and waste can flow freely out of the house. If these drain vents become blocked, it can cause your toilet to flush more slowly than normal. 

This issue can be a tricky one to fix because you must climb on the roof and locate the drain vent to fix it. If you aren’t comfortable with being on the roof or don’t know what to look for once you’re up there, you should call a professional plumber to resolve the problem safely and correctly. 

5. Clogged Trap Or Drain

Most people know what a clogged toilet looks like because it usually overflows, but when a toilet is only partially clogged, it will still flush, albeit inadequately or slowly. 

The first course of action to try if you think your toilet is flushing slowly due to a partial obstruction is to use a plunger. This is often enough to dislodge most clogs. If that doesn’t work, try a drain snake. A snake will often take care of obstructions like kids’ toys, flushable wipes, sanitary napkins, etc. to return your toilet to full flushing power once again. 

If, however, neither of these remedies fixes your slow-flush problem, you will need to consult a plumber as the issue could be somewhere beyond your reach. 

How To Fix A Slow-Flushing Toilet

I touched on a few simple solutions above, but let’s take a closer look at ways to fix a slow-flushing toilet. 

Slow Tank Flush Or Low Pressure

If the water level inside your toilet tank isn’t high enough, there won’t be enough pressure to force waste down the toilet drain. The water level should fall at about a half-inch below the overflow pipe. 

Adjust Tap Stop Float

Identify the type of float valves your toilet has. Ballcock mechanisms and cup floats usually have screws you can turn to adjust the water level inside the tank up or down. If your ballcock does not have a screw to turn, gently bend its rod up or down to change the water level accordingly. 

If your toilet has an internal fill valve, you must turn it counterclockwise to unlock it, move it up or down to adjust the water level, and then turn the valve clockwise to lock it into place again. 

Toilet Is Flushing Slowly

Replace Flusher Valve and Flapper

Replacing a worn flusher valve and the flapper is a more involved fix, but still relatively easy. First, you’ll need to turn the water off to the tank and flush the toilet to drain the tank. Next, remove the toilet tank by disconnecting the water line and removing the tank bolts. Carefully remove the tank from the bowl and place it upside down on the floor. 

Remove the old flush valve. You may need a spud wrench or a pair of slip-point pliers to do this. Insert the new flush valve into the opening, taking care to position the overflow tube facing the fill valve. 

Finally, reinstall the toilet tank and replace the flapper before reconnecting the water line. Turn the water back on and check for leaks. 

Water In Toilet Bowl Draining Slowly but not Clogged

Sometimes, a slow-flushing toilet can be caused by a clog that doesn’t fully block the drain. 

Soapy Water and Plunger

Most partial and full toilet clogs near the surface can be fixed using a plunger and soapy water. Simply squirt some dish soap into the toilet followed by a pan of boiling water. Use a plunger to break up the clog and coax it down the drain. 

Drain Snake

If the above method fails to return your toilet’s flushing power, there may be an obstruction further down. Insert a drain snake into the toilet and gently work it toward the clog. You might be able to feel when you’ve reached an obstruction. Once you do, pull the snake back out to remove anything that may be blocking the drain and restricting water flow. 

Professional Hydro-Jetting

If all else fails and your toilet is still flushing slowly, you may need to call a plumber to perform a professional hydro-jetting. Hydro-jetting forces a high-pressure stream of water into your home’s sewer system to remove stubborn clogs and buildup. 

You may also like to read Why Is My Toilet Randomly Running

FAQs Toilet Flushing Slowly

A slow-flushing toilet can be frustrating, so here are a few frequently asked questions answered. 

The toilet flushes slowly or not at all

When toilets flush slowly or not at all, it could be one of two things: the water level in the tank is too low, or the water in the bowl drains too slowly due to a blockage somewhere. 

The toilet flushes slowly and gurgles

A slow-flushing toilet that gurgles is a sign that there is a partial blockage somewhere in the wastewater system. 

The toilet flushes slowly and incompletely

A toilet that flushes slowly or incompletely may have an insufficient water level in the tank, mineral buildup, a partially clogged drain, a worn flapper/flush valve assembly, or a blocked drain vent. 

The toilet flushes slow and weak

The most common cause of a weak or slow flushing toilet is a low water level in the tank. Adjusting the float valve will fix the issue.

Toilet Flushing Slowly And Not Clearing – SOLVED

At this point, you know there are five common reasons why your toilet is flushing slowly: low water level, mineral buildup on jet holes, a partial clog, defective flush valve and/or flapper, and a blocked drain vent. Most of these issues can be fixed by an experienced DIYer following the information given above. Of course, if you aren’t comfortable making the repairs yourself, contact a reputable plumber near you for assistance. 

Plumber and HVAC Technician | Website | + posts

As a retired Master Plumber Jamie has over 30 years of hands-on experience, making his plumbing knowledge second to none. He has also worked on both residential and commercial HVAC installation and repair projects.