10 Common Causes of Slow Drains

 Slow drains are caused by hair, soap build-up, grease, food debris, mineral deposits, foreign objects or problems deeper inside the drainage system.

The sink still empties. The shower still works. So, it’s easy to leave it for another day.

Then one morning, the water barely moves at all.

That gradual slowdown can tell you that something is starting to restrict the flow. You might start looking up drain cleaner recipes or other ways to clear it, but what works depends on what is slowing the drain.

Plumbers see these problems every day, and knowing what slows a drain can help you work out what might be happening in your own home.

What Is Slowing Down Your Drain?

Has your shower been getting slower over the past month?

Does your kitchen sink struggle to drain after you wash the dishes?

Is it just one drain, or have your toilet, shower and basin all started behaving differently around the same time?

These are just a few of the questions a plumber might ask before doing anything to your drains. Your answers can give them useful clues about where the problem could be and what they should investigate first.

So, what could be slowing down your drain? Here are some of the problems that could be behind it.

#1. Hair Build-Up

Hair doesn’t slow a drain overnight. A few strands can become caught around the drain opening, stopper or further inside the pipe without causing any noticeable change at first.

As more hair collects, it can tangle together and catch soap residue and other material going down the shower or basin. Eventually, there is less room for water to pass through.

This is why you might notice your shower taking slightly longer to empty before you have an obvious blockage.

#2. Soap Build-Up

Soap looks like it disappears as soon as you rinse it away, but not everything necessarily travels all the way through the drainage system.

Soap residue can combine with body oils, hair and other material inside bathroom drains. Instead of creating one obvious obstruction, it can gradually leave deposits along the inside of the pipe.

You might first notice the problem in a bathroom basin, shower or bath that still drains but takes longer than it used to.

#3. Grease, Fats and Oils

Grease can be deceptive because it can go down the kitchen sink easily while it is warm.

Further along the drain, however, fats and oils can cool and collect on the inside of the pipe. Once that layer develops, food particles and other debris have somewhere to stick.

That’s why pouring cooking oil or greasy liquids down the sink can create a drainage problem further inside the plumbing, even when everything initially washes away without trouble.

#4. Food Scraps and Coffee Grounds

You finish making coffee, tip the grounds into the sink and rinse them away. They’re small, so it can feel like they’ll simply wash through the drain with the water.

But coffee grounds don’t dissolve when they get wet. Small food scraps and grounds can settle inside the drain or become caught in grease and other residue already lining the pipe.

The problem is repetition. Small amounts can settle inside the drain or become caught in grease and other residue already lining the pipe. Coffee grounds are particularly troublesome because they don’t dissolve when they get wet.

#5. Items That Shouldn’t Go Down the Drain

Some common items that can become lodged in drains include:

• Wet wipes

• Cotton buds

• Dental floss

• Paper towels

• Sanitary products

• Small toys or plastic pieces

• Jewellery and other small bathroom items

An item can become stuck while still leaving enough room for water to pass around it. This can explain why the drain continues working but becomes noticeably slower. It can also give hair, paper and other debris somewhere to catch, gradually making the obstruction larger.

#6. Mineral Deposits Inside Plumbing

The available space inside plumbing can gradually change as deposits accumulate.

Depending on the water supply and plumbing involved, deposits can include:

• Calcium deposits

• Magnesium deposits

• Limescale

• Rust and corrosion deposits

• Sediment carried through the water supply

These deposits can collect around fixtures, fittings and some internal plumbing surfaces. As the opening becomes narrower, water has less room to move through.

From the outside, everything can still look normal. The change is happening where you cannot easily see it.

#7. Tree Roots Can Reach Your Drains From the Yard

Root systems grow through the surrounding soil. They respond to conditions that support growth, including moisture, oxygen and nutrients.

If an underground sewer pipe already has a crack or another opening, moisture and nutrients can escape into the surrounding soil. Fine feeder roots growing nearby can enter through these small openings.

Toilet paper, fats and other waste can then become caught around the root mass, restricting the flow even further.

This is why clearing the material around the roots might restore drainage without solving the underlying problem. If the opening in the pipe remains, new root growth can enter the sewer line again.

#8. The Pipe Itself Could Be the Problem

Sometimes, though, there isn’t a typical blockage waiting to be pulled out or flushed away. The pipe itself could have:

• cracks

• displaced or separated joints

• a collapsed section

• deformation

• damage caused by ground movement

These problems can interfere with wastewater flow and create places where debris collects. A CCTV drain inspection can give a plumber a closer look inside the line and show if the condition of the pipe is contributing to the slow drainage.

#9. Drainpipes Need the Right Fall

Water going down a drain relies on gravity to keep moving through the pipe. That’s why the gradient, or fall, of the drainage pipe matters.

If a section doesn’t have enough fall, wastewater can move too slowly. A low or sagging section can also allow water and waste to sit in the pipe rather than continuing towards the sewer.

In this situation, clearing accumulated material can improve the flow temporarily, but the same section of pipe can continue collecting waste if the underlying drainage problem remains.

#10. Several Slow Drains Can Point to a Deeper Problem

One slow drain and several slow drains tell you two very different things.

If only your shower is draining slowly, the problem could be close to that particular fixture. But if the shower, basin, toilet and kitchen sink start draining slowly around the same time, the restriction could be further along a shared drain or sewer line.

Pay attention to which fixtures are affected and when the problem happens. That information can help your plumber narrow down where to investigate instead of treating every slow fixture as a separate problem.

Drain Cleaner Recipes You Can Try for a Slow Drain

Now that you know some of the common reasons a drain can slow down, you might be wondering what you can try before calling a plumber.

For light build-up, plumbers might suggest starting with hot water and dishwashing liquid to help loosen grease and oily residue. Another option is baking soda followed by vinegar and a warm-water flush for minor build-up near the drain opening.

But these drain cleaner recipes can only do so much. If your drain keeps slowing down, several fixtures are affected or the problem comes back after cleaning, it’s time to call a plumber.