4 Reasons Your Toilet Is Backing Up When it’s Not Clogged

There are several reasons why your toilet is backing up when it’s not clogged. The problem could be as simple as something caught in the trap or as challenging as a clog in your home’s main drain line outside. 

As frustrating as a toilet backing up can be, this problem is relatively simple to resolve. In fact, you may even be able to do it yourself. In some instances, however, you may need to call in a plumber to fix the issue as it could be something outside your home that’s causing the problem. 

This is a common plumbing issue, and nothing to be overly concerned about. Hopefully, by the time you’re done reading this article, you’ll know what’s causing your toilet to back up and feel confident enough to take the steps necessary to resolve it. 

No Visible Blockage In The Toilet Bowl

Just because you can’t see a clog doesn’t mean one doesn’t exist. There are several places along your home’s plumbing pipeline where waste and other debris can get caught up and block the flow of future flushes. 

You don’t see any blockage in the toilet bowl, you say? No worries! Often, a toilet that backs up has a more complex cause and you’ll need to dive deeper to figure out where the problem lies. Let’s look beyond the toilet bowl to find out what other issues might be causing your toilet to back up. 

Blockages Down The Toilet Pipeline

When most people think about toilet clogs, they picture a massive ball of toilet paper and waste stopping up the toilet bowl. While this happens quite often, a toilet backing up usually has a bigger issue somewhere further down the line. 

1. Obstructed P Trap or S Pipe

The P trap and S pipe on your toilet ensure that odors and gases remain in the sewer and cannot come up into your house. The design of these pipes is such that they also help keep foreign objects from getting too far down into your home’s plumbing. 

Many parents are familiar with the P trap because, for some reason, kids like to flush their toys down the toilet. When they do, the toy often gets stuck in the trap, and the toilet has to be removed to clear the blockage. If you’re the parent of a small child, this could be the reason your toilet backs up when flushed. The toilet paper and waste can’t make it past the blockage in the trap and has no choice but to come back up. 

Depending on the object or debris stuck in the trap, you might be able to use a toilet snake to clear the blockage. If that doesn’t work, you may need to take the toilet out completely to unclog it from the bottom. Alternatively, you can also call a plumber to remove the blockage if you aren’t comfortable doing so yourself. 

2. Blockage in The Toilet Waste Drain Pipe

If the P Trap isn’t the problem, the blockage could be just past the toilet in your home’s waste drainpipe. This is the pipe that connects the toilet to the main drain line outside. Unfortunately, if the blockage occurs here, you probably won’t be able to reach it yourself. It will likely require specialized equipment that only a professional has. Even if you could reach the blockage in your home’s drainpipe, you run the risk of causing major damage to the plumbing, so it’s best to leave this resolution to the pros. 

The good news is that you can diagnose this issue yourself before calling a plumber. To see if this is the cause of your toilet backing up when it’s not clogged, flush the toilet and watch the shower and sink drains in the room. Do you hear or see water bubbling up the drains with each flush? If so, you definitely have a blocked drainpipe. Typically, a plumber will be able to fix this issue from inside the house but keep in mind that this could be a precursor to a bigger problem. 

3. Blockage In The Mainline Waste Pipes

The mainline waste pipes connect your home to the city’s sewer system outside. These pipes are underground and much harder to reach should a blockage occur there. This issue is also much more costly to fix than a clog inside your home. And before you ask, just because these pipes are outside and underground, they are still your responsibility as the homeowner – not the city. 

To diagnose a mainline pipe blockage, do the same thing as suggested in the last section. Flush the toilet. This time, however, watch the other drains on the first floor and basement level of your home. Do you hear or see water bubbling up? Run the washing machine. Does doing so affect other drains in your home? If you answered yes to any of these questions, you likely have a mainline waste pipe blockage that will probably require the skill and know-how of a trained professional and a fair amount of digging in your yard. 

4. Blocked Sewer Vent Trap 

Every home’s plumbing system has to be vented outside. This venting system allows noxious gases and odors to escape outside and not into your home. Sometimes, this vent trap can become clogged, which causes stagnant water to sit in your home’s pipes. Once the pipes fill to capacity with this unmoving water, it will begin backing up into your home’s drains and toilets. 

In most cases, the vent trap is located on the roof of the home. While it is possible to reach it yourself, many people are hesitant to climb on the roof to clear a blockage themselves. In the case of a blocked vent trap, it’s best to call a professional with the right equipment and skill to resolve the issue. 

Household Drain Line Vs Sewer Mainline

In this article, I’ve talked a lot about the different drainpipes inside and outside a typical home. It can be a bit confusing to understand the differences, so let me explain. 

Your home’s drain lines are the ones that run inside and throughout your home. You can probably reach a clog in any of these pipes yourself. 

The sewer main line is the waste pipe that connects your home to the city’s sewer system. These pipes run underground in your yard and deliver all your home’s gray and black wastewater to the sewer system under the street. If your home isn’t connected to the city’s water and sewer systems, you’ll have a private sewer system in your yard that requires emptying every few years. 

How To Clear A Clogged Toilet Drain Line

As I mentioned earlier, most clogs in a home’s drain lines can be addressed from inside the home by any avid DIYer. Of course, if you aren’t comfortable doing so, you can always call a plumber. If you want to try to clear a blockage yourself, I suggest the following methods. 

Try a Plunger To Clear The P Trap

A tried and true method to clear a blockage that causes your toilet to back up is plunging. A plunger is often enough to move a clog in the P Trap along. 

Pour Dish Soap To Lubricate the Drain Pipe

If plunging the toilet doesn’t move the blockage along, you can try adding dish soap to the bowl. Simply pour a good amount of dish soap into the toilet bowl and allow it to sit for a while so it coats everything, which will enable any waste or other debris to slide right on down the drain. After allowing the dish soap to sit for a while, try plunging again. The clog should release and move along easily. 

Use a Drain Snake

If the dish soap method fails to do the trick, your next option is to use a drain snake. Be sure to get one designed to clear toilet clogs, so you don’t cause undue damage to your toilet’s plumbing. 

Insert the snake into the toilet drain and gently guide it down slowly until you feel resistance. The resistance is whatever is clogging the pipes. Work the snake back and forth to dislodge the blockage. Be aware that the snake will probably bring back with it the material that was clogging the drain line. 

Lift The Outdoor Drain Line Cover In Your Yard

Locate the drain line cover in your yard and remove it. You may or may not see the blockage there. Clogs often form at the junction of several drainpipes before reaching the mainline drain. In most cases, you probably won’t be able to clear blockages here yourself, but a plumber may use drain rods to loosen the blockage so it can be blasted away with a strong jet of water. 

When a toilet backs up with no apparent clog, it can be frustrating. Right away, many people think the worst, expecting a hefty bill to fix the issue. Hopefully, the information I’ve supplied above will help you figure out why your toilet is backing up when it’s not clogged, so you can either fix it yourself or get a professional in to resolve the issue as soon as possible.

FAQ’s Toilet Is Backing Up When Not Clogged

How do I know if my main sewer line is clogged?

Signs that your main sewer line could be clogged include multiple backed-up drains, gurgling noises, slow drains or no drainage, foul odors, and sewage backups.

Plumber and HVAC Technician | Website

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.