A bathtub should drain full in 2 to 4 minutes. If takes way longer than that, there is an underlying problem that you need to attend to.
A slow draining bathtub is caused by hair, mineral deposits, soap scum and other bathroom products accumulating in the drain and trap. The accumulation restricts the free flow of water and hence the bathtub drains slowly.
It could also be caused by a clogged vent stack, which causes negative air pressure to build up inside the drainpipe. A clogged main house drainpipe or a full septic tank could also cause a bathtub to drain slowly.
If a slow draining bathtub is not fixed, the drain will become completely blocked causing a clogged bathtub with standing water. Unclogging a bathtub with standing water is a lot harder than a slow draining bathtub.
To fix a slow draining bathtub, remove the bathtub stopper and fish out the hair and other gunk using a hooked wire. Pour equal parts of baking soda and vinegar and after 30 minutes run hot water down the drain.
If that doesn’t fix it, use a plunger or a drain snake to clear the drainpipe.
How a Bathtub Drain Works
It is always important to know how something works if you want to fix it and also understand how to maintain it to prevent problems in the future.
A bathtub, just like all the other fixtures in your house has a small pipe just below the drain opening called a trap. You can see a trap on the side of your toilet or a under your bathroom or kitchen sink.
A drain trap is a U-shaped piece of the drainpipe that holds a little amount of water at all times. The water acts as barrier, preventing sewer gases from coming up to the house. That is why when you travel for a few days and the water in your drain traps evaporates a sewer gas smell lingers in the house.
Another function of the drain trap is to hold potential drain clogs, preventing them from clogging the drainpipe further down the drain. Unclogging a drain trap is way easier than a clog that is about 10 feet away.
Whenever your bathtub is clogged or draining slowly, it means that your drain trap is blocked and hence water from the tub cannot drain out freely.
A vent stack is the vertical pipe that runs from the main house drainpipe through the roof of the house. It is responsible for removing sewer gases from the drainpipe, allowing fixtures to drain easily. If the vent is clogged then the bathtub will draining slowly as a result of air pressure trapped inside the drainpipe.
A blocked vent stack will affect other fixtures in the house as well. If you notice that your toilet bubbles as the bathtub drains or your bathtub gurgles when the toilet is flushed then you have a clogged vent stack, or sometimes a clogged main house drainpipe, full septic tank or the sewer line itself is clogged.
How to Unclog a Slow Draining Bathtub
Unlike unclogging a toilet, to successfully unclog a slow draining bathtub you first need to remove most of the trash out. As we have seen, most of the hair, grease, soap scum and other debris are found between the bathtub drain opening and the drain trap.
Steps to clear a slow draining tub:
If the Drain is Full of Hair
When the bathtub stopper is out, it is time to unclog the bathtub. Here is how to unclog a slow draining bathtub with a coat hanger or wire:
- Head to your closet and grab a wire coat hanger.
- Cut it and straighten it using a pair of pliers. If you cannot get a wire coat hanger, look for a firm and thick wire that is about 1 feet long.
- Using the same pliers, make a small hook on one end of the wire.
- Insert the hooked end of the wire inside the bathtub drain and start fishing out the strands of hair and other gunk. Remove as much trash as possible.
Use Baking Soda and Vinegar
After you have removed most of the trash with the hooked wire, it is time to dissolve all the hair, soap scum and mineral deposits with baking soda, vinegar and hot water.
- Pour 1 cup of baking soda down the bathtub drain.
- Slowly add 1 cup of vinegar. I must insist that you should add the vinegar slowly as it reacts very fast with the baking soda and could raise up and splash on your face. The reaction between baking soda and vinegar will dissolve and loosen the clogs, making them to wash down the drain easily. Wait for 30 minutes for the solution to work out.
- After the time has lapsed, run hot water down the bathtub drain for about a minute. The hot water will further dissolve the soap scum, calcium deposits as well as wash down any loosely held hair strands in the drainpipe
This is one of the best method to unclog a slow draining bathtub without a plunger or snake. It is also the best way to unclog a bathtub naturally, especially for people on a septic system as chemical drain cleaners will kill the good bacteria in a septic tank.
Without Removing the Stopper
Although we have seen that removing a stopper is quite a simple task, some people will still prefer to unclog a bathtub without having to removing the stopper.
The best method for unclogging a bathtub when you don’t want to remove the stopper is to use a plunger. While a plunger on its own maybe sufficient it is always good to complement it with other methods.
Here is how to effectively plunge a bathtub:
- Pour half a cup baking soda down the bathtub drain.
- Slowly add a cup of vinegar and wait for about 30 minutes.
- Blast hot water down the bathtub drain after the 30 minutes.
Chances are that the above steps are enough to unclog a slow draining bathtub without having to remove the stopper. If it doesn’t, that is where the plunger comes in.
- Place a plunger over the bathtub drain and make sure that there is some water in the bathtub, enough to cover the bottom of the plunger.
- Before you start plunging, cover the overflow drain. This will help you avoid pressure loss and as a result have a stronger siphon. If you have an extra plunger, have someone hold it tightly over the overflow drain. Stuff a rag inside it if you only have 1 plunger.
- Start plunging the bathtub, starting off gently, and then aggressive plunging for 2 minutes.
- Check if the water in the tub is draining quicker now. If not plunge some more.
Snake the Drain
If plunging doesn’t make your bathtub drain quicker, you need to upgrade to a drain snake. A drain snake consists of a hooked spring-like head, flexible cable and a cranking handle. The cable is usually rolled in a drum.
Please do not use a toilet auger to unclog a bathtub. A toilet auger is designed specifically to unclog toilets, while at the same time prevent scratching them.
If your bathtub has a trip-lever bathtub stopper, you will need to remove it. It is advisable to snake a bathtub through the overflow drain and not the drain hole.
Here is how to remove a trip-lever bathtub stopper:
- Locate the 2 screws on the overflow drain cover plate. Remove them with a screwdriver.
- Once the screws are out, grab the cover plate and pull the entire assembly out. You first pull it upwards and then outwards. If the stopper has been in place for a long time, it might be sticky. More on how to remove a stuck trip-lever bathtub stopper here.
Once the stopper is out, it’s time to snake the bathtub. Here is how to snake a clogged bathtub:
- Loosen the clamp on the drum. This will free the cable as you push it in the drain.
- Carefully insert the snake head through the overflow drain and start pushing the cable down until you encounter resistance.
- Tighten the clamp on the drum.
- Slowly start turning the crank handle clockwise. Whenever it feels hard reverse the direction and start over again. Don’t force it.
- When the handle feels free, it means you have gone through the clog. Release more cable and push it further down just in case there are more clogs.
- When you are satisfied that the bathtub is fully unclogged, pull the cable back to the drum. As you pull the cable out, hold a rag firmly around it to clean it.
- Put back the tub stopper pretty much the same way you removed it, being careful not to have the 2 link rods entangled.
Tub Not Clogged? Unblock the Vent Stack
Dead birds, rodents, dry leaves and even snow can clog your vent stack. When that happens, air cannot flow out of the drainpipe and is hence trapped in the pipes.
In order for fixtures to drain properly, there must be air circulating in the drainpipe. When that does not occur as a result of a clogged vent, you will have a bathtub that is draining slowly as well as a weak flushing toilet.
- Take a ladder and climb to the top of the house, a garden hose in hand.
- Check if there is trash at the top of the pipe that you can easily remove with your hand.
- Insert the garden hose down the vent to see if you can feel any blockage.
- If you notice any obstruction, have someone turn on the water to the hose. The weight of the water is often enough to unclog the vent. The leaves or dead birds will wash down the drain.
- If the water doesn’t unclog the vent, upgrade to a more powerful tool, the drain snake.
- Feed the snake down the vent and snake it until the vent is unblocked.
Problems with the Main Line?
Your bathtub drainpipe terminates into the main house drainpipe. The main house drainpipe is connected to your city’s sewer line.
If your main house drainpipe is clogged, your fixtures the bathtub included will be draining slowly. Check if that is the same thing happening with your washing machine or kitchen sink.
The drainpipe does not even have to be fully clogged. A partial clog in your drainpipe means that water is passing through slowly, and that could be one of the reasons your bathtub is draining slowly as well.
Unfortunately, a clog in the main house pipe is not something you can easily unclog on your own. You will most likely need the services of a professional plumber.
Plumbers have drain cameras that will accurately diagnose the cause of every plumbing problem in your house and you should therefore not hesitate from calling one.