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Why Your Bathroom or Kitchen Sink Is Backing up into the Tub & How to Fix It

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  • Getting into the bathtub for a good soak is like claiming a piece of heaven right in your own home. But when dirty water starts backing up into the tub, well, let’s just say it can be a hellish experience.

    It becomes even worse when you realize that all that dirty water came from the kitchen sink or *gasp* the bathroom.

    On this page:

    Obviously, you need to get that thing fixed. After all, a life without a good soak during your nightcap is no life at all.

    But what’s causing dirty water to back up into the tub while the bathroom or kitchen sink is being used?

    You probably have a clog.

    And if you want to claim your piece of heaven again, you need to find out where the clog is coming from so you can have it removed.

    But first, you need to get familiar with how your drain system works.

    A Primer on the Anatomy of Your Drainage System

    Before you proceed, it bears noting that your sinks and your bathtub are connected to each other via one drainage system.

    Imagine your drainage system’s main sewer line as one big river, with your kitchen sink, bathtub, toilet, and other bathroom drains serving as its tributaries. Since the main sewer line (the main river) is much larger than the other drains (tributaries), it’s capable of handling the water being drained from the aforementioned fixtures– even all at once.

    Below every drainage fixture is a curved section called the P-Trap or the U-trap (if it’s shaped like a “U”). That curved pipe is there to keep the water flowing from the drain line at bay, preventing sewer gases from escaping. If you’ve ever wondered why your bathroom doesn’t end up smelling like sewage (at least most of the time), it’s because of the P-trap (or U-trap) underneath your toilet.

    Now imagine the entire household continually dumping soap suds, hair, food articles, and who-knows-what-else into the drains over a long period… where do they go? That’s right, some of that stuff eventually get caught in the P-trap, causing it to get clogged. This can slow down the draining action inside your pipes. If left unattended for too long, that clog can get worse, resulting in a fully-blocked P-trap. Once this happens, your tub or sink won’t drain at all.

    But if the tub is backing up water, that means the P-trap is clear, right? 

    Exactly. But the fact that it’s spitting up water in short bursts could only mean that there’s still a clog. The only difference is that the clog is located below (or far below) the P-trap. In other words, the clog is located somewhere inside the sewer line. This causes water to get redirected into the other drains every time you use a plumbing fixture. Flushing the toilet, for example, can cause the tub or shower to spit up water.  Even operating your dishwasher can cause water to  back up into the kitchen sink.

    The common causes of sewer clogs

    To give you a good idea of what you might be dealing with, below are the common causes of sewer clogs.

    1. Tree roots

    Tree roots always look for water sources and may end up forcing their way into your sewer lines, especially if your pipes have cracks and leaks.

    2. Grease

    Grease is one of the most common things that are fed into drains, especially in the kitchen. It can be very tempting to just dump cooking grease and oil down the pipes once you’re done with cooking. It doesn’t help that many food items such as butter, mayonnaise, cheese, and cake contain grease.

    3. Hair

    Hair strands are notorious for causing drain blockages because they facilitate the formation of clogs when mixed with grease and sticky substances. Install a guard on the drain to catch hair and make sure to clear it regularly.

    4. Food scraps

    Most people think they can dump food waste down the drain without facing the consequences just because they have a garbage disposal in the sink. As already mentioned, most food items contain grease, which is notorious for creating clogs over time. Other food items such as coffee grounds or tea leaves are also difficult to break down. To prevent drain blockages, dump food waste into a compost pile instead (more on this later).

    5. Trash items (wipes, feminine products, tissue paper, plastic, etc.)

    As a general rule, the only trash item you can dump into your toilet is toilet paper. But even toilet paper can cause clogs if there’s too much of them being flushed into the toilet.

    Other possible reasons why your plumbing drains are backing up into the tub

    While a clogged drain line is the most likely reason why your kitchen or bathroom sink is backing up water into the tub, there are other possible causes you might want to consider. After all, carrying out the wrong solution not only wastes your time, but it can also compromise your drainage system further.

    Here are other possible causes why your bathroom or kitchen sink is backing up water into the bathtub.

    Venting issues

    Your drain’s pipes need to maintain the right amount of air pressure to ensure that the drainage system can properly dispose of sewage and grey water. This is why every drainage system has venting pipes running through it. If one or more of your venting pipes becomes defective, the negative pressure may cause wastewater to back up into one of your plumbing fixtures.

    Venting issues are usually caused by a missing or broken vent line, or clogs.

    Replacing a missing vent line yourself can be a lengthy process, not to mention that you may be required to obtain a permit from your local government. As such, the best solution is to hire a professional plumber to find a proper replacement and to do the installation for you. A broken vent line also requires a similar solution because, believe me, fixing it yourself will be more trouble than it’s worth.

    But if you’re dealing with a clogged vent pipe, someone must climb on your roof and use a snake auger to remove the blockage.

    Septic tank is full

    If you haven’t pumped your septic tank for a long while, chances are it’s brimming fit to burst, which may be causing your bathtub to back up every time water is being pushed down the drain. The force of the water becomes even stronger if there’s too much pressure build up. The water usually drains into the bathtub first because it’s typically lower than your bathroom or kitchen sink. You must pump your septic tank at the earliest sign of an overflow. Otherwise, the sludge will continue to build up and might damage the drain field.

    Sewer line is damaged

    A broken sewer line may prevent sewage water from flowing through the pipes and may back up into the tub as a result. The problem with a broken sewer line is that you are more likely to notice it only once the damage becomes severe.

    As is the case with most things, prevention is the best cure. If you find growing trees near the sewer line, you must check if roots have started to penetrate your pipes. If they have, it’s recommended that you hire a professional plumber to remove the roots and repair the pipes.

    If the sewer line is already old, the better option is to have it fully replaced. You’ll end up wasting your time and money if you carry out repairs only for the sewer line to break down again.

    How to fix a sink that is backing up?

    If your bathtub is backing up, you might want to examine your kitchen sink, too. Remember the river analogy? All drains feed into the main sewer line.

    First off, don’t bother using a plunger. In cases where backed up water is involved, the clog is already past the point where the kitchen sink and bathtub drains converge. In other words, the blockage is far too deep inside the sewer line for the plunger to have any effect.

    But don’t worry, there’s a tool that is made to deal with blockages like these.

    That tool is called the toilet auger, otherwise known as the snake auger.

    Made out of a long, flexible metal with an auger bit at one end and a crank handle at the other, a toilet auger can snake or maneuver its way through the drain to remove or dislodge clogs. If the clog is far too deep for your plunger to dislodge, the snake auger is the tool that can do it for you.

    Things could get messy if you don’t know what you’re doing, so here’s a step by step tutorial on how to unclog a sewer line with a snake auger. (Disclaimer:  Snake augers vary in design and functionality, so make sure to check the user manual that came with the package before you carry out the following procedures):

    1. Position the auger bit into the mouth of the toilet.
    2. Start feeding the snake into the drain (make sure the plastic coating around the tip is intact to avoid scratching the porcelain).
    3. Allow five inches of cable between the toilet’s inner opening and the handle pipe’s end.
    4. Once the snake is in position, start rotating or cranking the auger using the handle.
    5. Push the snake steadily through the drain (its flexible coils should make it easy for you to maneuver through the pipe’s contours as you unwound the snake).
    6. If the auger doesn’t bend, pull it back a bit while cranking the handle counterclockwise before giving it another go.
    7. You’ll feel some resistance when you reach the clog. Give it a little shove and continue cranking the handle until the auger bit clears the clog.
    8. If it’s taking a while to clear the pipes, crank the handle in the opposite direction while pulling the snake out. Keep repeating this procedure until you’ve completely unclogged the pipe.
    9. After unclogging the pipe, flush the toilet to ensure that the clog won’t get caught inside again.
    10. If you’re unsuccessful in your attempt to clear the drain, your best option is to hire a professional plumber.

    Signs your drains are clogged

    Now that you’ve unclogged your drains, you’d do well to prevent it from getting clogged again. Early detection is key if you want to pull that off. The longer you leave a clog unattended, the more difficult it will be to clear it from your drains.

    The earlier you spot the telltale signs, the faster it will be for you to remedy the situation. Better yet, early detection prevents you from costly repairs.

    Here are the signs you need to look for to check for clogs.

    Unpleasant odors

    If you’re getting a whiff of something unpleasant and you’re having a difficult time finding the source, chances are it’s coming from a clogged drain. Food scraps that get trapped inside drains fester over time. As soon as you detect the offensive smell, you’d do well to address the issue before the clog (and the smell) gets worse.

    You’re hearing gurgling noises

    Gurgling sounds from drains can be worrisome. There are two possible reasons why your drains are making that noise. One, you may be dealing with a partially clogged drain. Two, your plumbing vent might be damaged.

    Partial clogs prevent the smooth flow of water inside pipes, creating instances of trapped air. That air is typically displaced or released due to a plumbing mechanism (such as when you run the bathtub), which causes the gurgling noises.

    Gurgling sounds also happen frequently when one or more of the drainage system’s plumbing vents are defective. When you don’t have a proper mechanism that regulates your piping’s atmospheric pressure, the irregular water flow is likely to create a vacuum. Once that vacuum pops, the air is released through the P-trap, which creates those dreadful noises.

    Clogs make it difficult for water to pass through the sewer line properly, causing some of it to shoot back up into your bathroom or kitchen drains. Backed-up water is obviously dirty, and long-time exposure to it can’t be good for your health.

    Water is draining slowly

    This is perhaps one of the most obvious signs that your drain is partially blocked. If your tub or sink is taking too long to empty out, then something in the drainage system is stopping the water from coming down.

    Plants near the sewer line

    Plants or trees growing near the sewer line pose a threat to your pipes. For one thing, tree roots are naturally drawn to water,  making the drainage system a potential target for their growth spurts. If left unchecked, a root can penetrate the pipe, causing a major blockage.

    Protip: To prevent roots from taking over your pipes, try installing metal or wood barriers around the sewer lines.

    How to prevent future clogs in your drains

    As a homeowner, you have everything to gain by making sure that everything in your home is in good working order. Your drains, most of all, requires your utmost attention. Can you go through an entire day with your pipes busted? Thought so.

    So let’s get to it: Here are the precautions you need to take to prevent your drains from getting clogged.

    Don’t dump grease into the drains

    We love stuffing ourselves with fatty foods like chips, french fries, pizza, and hamburgers. That said, you better keep them away from your drains. Why? Because as we discussed earlier,  fatty foods contain grease. Grease and drains don’t mix!

    When grease is fed into the pipe, it starts to slowly congeal until it becomes solid and hard enough to form a blockage. That clog can only get thicker and harder as food scraps, hair, and other debris gets caught along with it.

    Catch hair before it goes down the drain

    Hair is notorious for causing drainage clogs. When you’re enjoying a hot shower or having a good soak in the tub, the last thing you want to do is keep count of how many hair strands are getting caught in the drain.

    Thankfully, installing a hair catcher in your tub or sink addresses this problem right away. Affordable and easy to use, a hair drain catcher provides you a filter that keeps hair from entering the drains.

    Collect organic food waste and dump them in a compost pile

    Grinding up food waste before feeding them down the drain isn’t enough to prevent your drains from getting clogged up. You’d be doing your pipes a big favor by dumping food scraps into the trash. It’s even better for the environment if you dump them into a compost pile or a compost bin (word of caution: don’t throw greasy food into the bin because they take a long time to break down). If there’s no food waste recycling collection service in your area, you can build your own compost bin instead.

    Don’t throw stuff into the toilet

    This should be a no brainer, but sadly, many homeowners still treat their toilets like a wastebasket. Again, the only personal care product you’re allowed to feed into the drain is toilet paper. Full stop. If you’ve been throwing dental floss or cotton buds in there, then don’t be surprised if your toilet isn’t draining properly every time you flush.

    Mistakes to avoid when cleaning drains

    Most homeowners tend to become overeager when cleaning drains. They pull up their sleeves and set out to do the dirty work themselves. The problem? Most of them make the problem worse by using the same erroneous methods.

    Here are common mistakes to avoid when cleaning your drains:

    Overusing chemical drain cleaners

    Those drain cleaners can work wonders for your clogs, or at least that’s what we’re seeing on TV. In truth, they’re not usually effective at clearing clogs. Besides, using a chemical drain cleaner can eliminate only a small portion of the clog. Also, the partial clog you eliminate through drain cleaners is likely to come back. Worse, drain cleaners contain harsh chemicals that can wreak havoc on your pipes, which may lead to costly repairs.

    Fishing out clogs with a stick or a coat hanger

    Even in this day and age, too many homeowners still use a straightened out coat hanger or stick to try to clear their clogged drains. This is a big mistake. For one thing, these objects may get stuck inside pipes, and the action of trying to pull it out may cause more damage. Besides, you can’t unclog a pipe just by pushing on it with an object. Besides, you may only end up pushing it deeper down the drain.

    Using a garden hose

    The idea of using a garden hose to clear drain blockages is too good to be true. Sure, it may be able to eliminate clogs. The only problem is that it can cause damage to your pipes as well.

    Make sure to also read our guide if you ever see water dripping from the bathroom exhaust fan.

    Getting help from pros

    Everyone deserves a home with good plumbing. After all, it can be difficult for most of us to go through the day while our plumbing fixtures are spitting up dirty water. Make no mistake—we need to properly maintain our drainage system if we are to maximize its benefits.

    But let’s face it: clogs do happen no matter how careful we are about the stuff we feed into our drains. And while going the DIY route can save you money, there are specific scenarios where you have to leave it to the professionals. A professional plumber, after all, has the required skills, extensive training, and the experience needed to do the job properly. We can’t afford “quick fixes” that may do more harm than good.

    Of course, not all “pros” are good at what they do. As are all things in life, there will always be bad apples. But there are steps you can take to ensure that you don’t pick the rotten one from the basket.

    One such step is to get as many quotes from different competing contractors as you can. The more options you have, the better the chances you will find the right fit.

    Getting quotes, however, can be time-consuming, not to mention costly.

    But here’s an idea: how would you like to receive up to 4 FREE quotes from competing bathroom contractors without having to do any of the typical legwork?

    Just fill out our form and you’ll receive your quotes in no time! More importantly, you’re not under any obligation to accept any of the offers if none of them are to your liking. Either way, filling out our form enables you to take the first big (and risk-free) step to find a contractor who will charge you fairly and take care of your plumbing needs.

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