What Causes Drain Clogs? The 8 Most Common Causes and How to Prevent Each

Cause #1: Hair (Bathroom Drains)

Hair is the number one cause of bathroom drain clogs, and it's almost entirely preventable. The mechanism is straightforward: loose hair enters the drain, catches on the drain stopper or pipe walls, and combines with soap scum and hard water minerals to form a dense, sticky mass. This mass grows over weeks and months until it restricts or completely blocks water flow.

What makes hair clogs particularly stubborn is the combination of materials. Hair alone would wash through most pipes. But hair coated in soap scum — which is itself a combination of bar soap fat and hard water minerals — becomes a dense, adhesive plug that grips the pipe walls and catches additional debris with every shower.

Prevention: Install a drain hair catcher on every shower and tub drain. Clean it weekly — this takes about 10 seconds and eliminates the vast majority of bathroom drain clogs. This is the single most effective drain maintenance step a homeowner can take.

Fix: A drain snake or Zip-It tool (a plastic barbed strip available at any hardware store) can usually clear a hair clog in minutes. Do not use chemical drain cleaners — more on why below. Our article on slow drain causes covers bathroom drain issues in more detail.

Cause #2: Soap Scum and Hard Water Scale

Bar soap contains animal fat or vegetable fat as a base ingredient. When this fat combines with the calcium and magnesium minerals in hard water, it forms soap scum — a waxy, grayish residue that coats pipe walls, narrows the pipe's effective diameter, and catches hair and other debris. Over time, soap scum buildup can significantly restrict flow in bathroom drains.

Maryland well water is frequently hard — many areas of Calvert County and Anne Arundel County have water hardness above 10 grains per gallon (GPG), which is classified as "very hard." This accelerates soap scum formation dramatically compared to areas with soft municipal water.

Prevention: Switch from bar soap to liquid body wash, which doesn't contain the same fat-based ingredients and produces far less soap scum. Installing a water softener addresses the root cause by removing the calcium and magnesium that react with soap. Our guide to what hard water is and how it affects your plumbing explains this chemistry in detail.

Fix: For significant soap scum buildup coating the pipe walls, hydro jetting is the most effective solution. A drain snake can clear a blockage but won't remove the scum coating the walls — the clog will return quickly.

Cause #3: Cooking Grease and Food Waste (Kitchen Drains)

Grease is the most common cause of kitchen drain clogs — and one of the most misunderstood. When hot cooking grease enters the drain, it's liquid and seems harmless. But within 20–30 feet of travel through your pipes, it cools and solidifies on the pipe walls. Each cooking session adds another thin layer. Over months and years, these layers accumulate until the pipe's effective diameter is dramatically reduced.

The problem is compounded by food particles — coffee grounds, eggshells, pasta, rice, and produce scraps — that get caught in the grease coating and accelerate the buildup. Pasta and rice are particularly problematic because they absorb water and expand inside the pipe, turning a minor restriction into a complete blockage.

Prevention: Cool cooking grease and dispose of it in the trash — never down the drain. Use a sink strainer to catch food particles. Run cold water (not hot) when using the garbage disposal, which helps solidify grease so it passes through rather than coating the walls. Our detailed article on grease in drain pipes covers the full progression of grease buildup and why it's so difficult to reverse.

Fix: Snaking a grease clog punches a hole through it but leaves the grease coating on the pipe walls — the clog returns within weeks. Hydro jetting is the correct solution for grease buildup because it physically scours the grease from the pipe walls. Our hydro jetting service is available throughout Calvert and Anne Arundel County.

Cause #4: "Flushable" Wipes and Non-Flushable Items (Toilets)

"Flushable" wipes are one of the most damaging consumer product myths in existence. Unlike toilet paper, which is specifically engineered to break down rapidly in water, wipes are designed to be durable and maintain their structure when wet. They do not disintegrate in the sewer system. Instead, they accumulate at pipe bends, joints, and any point of restriction — catching additional debris and eventually forming a complete blockage.

The same applies to paper towels (far thicker and more durable than toilet paper), cotton balls, dental floss (which tangles around other debris and creates a net-like obstruction), feminine hygiene products, and medications. None of these items belong in a toilet.

Prevention: The rule is simple: only human waste and toilet paper go in the toilet. Post a reminder in bathrooms used by guests or children. Keep a small trash can next to every toilet for everything else.

Fix: A drain snake can usually clear a wipe clog if it's localized. For wipes that have accumulated further down the line or combined with other debris, hydro jetting may be necessary. Our drain cleaning service handles both scenarios.

Cause #5: Tree Roots (Main Sewer Line)

Tree root intrusion is the leading cause of main sewer line clogs in Maryland. Roots are drawn to the warmth and moisture inside sewer pipes, entering through pipe joints, cracks, and any deteriorated section. Once inside, they grow to fill the available space — catching toilet paper, wipes, and other debris until the pipe is completely blocked.

This type of clog is fundamentally different from the others on this list because it's not caused by what goes into the drain — it's caused by what's happening to the pipe itself. No amount of behavioral change prevents tree root intrusion. The only solutions are detection, treatment, and (in severe cases) pipe repair or replacement.

Prevention: Schedule a sewer camera inspection every 3–5 years to catch root intrusion before it causes a backup. If roots are detected early, annual copper sulfate or foaming root killer treatments can slow regrowth. Avoid planting trees within 20 feet of your sewer line.

Fix: Mechanical root cutting combined with hydro jetting removes existing roots. For severe or recurring intrusion, pipe lining (trenchless rehabilitation) or pipe replacement eliminates the problem permanently. Read our full guide on tree roots in sewer lines for a complete treatment overview. You can also schedule a sewer camera inspection to assess your current situation.

Cause #6: Mineral Buildup (Hard Water Scale)

In areas with hard water — which includes much of Calvert County and Anne Arundel County — calcium and magnesium deposits (collectively called scale) accumulate on the interior walls of pipes over time. Unlike grease, which is soft and can be cleared with hydro jetting, mineral scale is hard and crystalline. It narrows the pipe's effective diameter gradually over years, reducing flow and eventually contributing to complete blockages.

Scale buildup is particularly common in hot water pipes, where the heat causes minerals to precipitate out of solution more rapidly. You may notice it first as reduced flow from hot water fixtures, or as white or yellowish deposits around faucet aerators and showerheads.

Prevention: A water softener is the most effective long-term solution. By removing calcium and magnesium from the water supply before it enters your pipes, a softener prevents scale formation throughout your entire plumbing system. Our guide to choosing a water softener can help you select the right system for your water hardness level.

Fix: Descaling treatments using acidic solutions can dissolve mild to moderate scale buildup. For severe cases where scale has significantly narrowed the pipe, pipe replacement may be the most practical solution.

Cause #7: Foreign Objects

Small objects — children's toys, bottle caps, toothbrush caps, jewelry, and similar items — occasionally fall into drains and create blockages. These are usually sudden rather than gradual: the drain works fine until the object enters, then stops working immediately or within a short time.

Foreign object clogs are more common in homes with young children, who are naturally curious about what happens when things go down the drain. They're also common in bathroom sinks where small items are frequently handled near open drains.

Prevention: Install drain covers on all drains. Keep small items away from open drains. Teach children that drains are not toys.

Fix: A drain snake can sometimes retrieve or push through a foreign object. For objects that are lodged at a bend or fitting, camera-guided retrieval may be necessary. Do not attempt to retrieve objects by disassembling drain pipes unless you're comfortable with plumbing work — an improperly reassembled drain connection can cause leaks inside walls or under floors.

Cause #8: Pipe Deterioration (Older Homes)

In homes built before the 1980s, the pipes themselves may be the cause of recurring clogs. Cast iron drain pipes corrode from the inside over decades, developing rough, pitted surfaces that catch debris and accelerate buildup. Clay tile sewer pipes develop cracks and joint separations that allow root intrusion and create flow restrictions. Orangeburg pipe — a tar-paper composite used from the 1940s through the 1970s — softens and collapses over time, creating severe flow restrictions and eventual complete blockages.

If you have an older home and experience recurring clogs despite proper drain habits, pipe deterioration may be the underlying cause. No amount of snaking or hydro jetting permanently solves a clog caused by a collapsed or severely corroded pipe. Our article on cast iron pipe problems covers the signs of internal corrosion in detail.

Prevention: Schedule a sewer camera inspection to assess the condition of your pipes. This is especially important if you're buying an older home — our guide to plumbing inspections before buying a home explains what to look for.

Fix: Trenchless pipe lining can rehabilitate deteriorated pipes without excavation in many cases. For severely collapsed or offset pipes, replacement is necessary. Our sewer repair service covers both approaches.

Why Chemical Drain Cleaners Are a Bad Idea

Chemical drain cleaners — Drano, Liquid-Plumr, and similar products — are one of the most commonly misused plumbing products. They seem like a convenient solution, but they cause more problems than they solve.

Lye-based drain cleaners work by generating heat through a chemical reaction. This heat can soften PVC pipe, damage rubber gaskets and seals, and accelerate corrosion in older metal pipes. They're also dangerous: if they don't fully clear the clog, you now have a drain full of caustic chemical that a plumber must work around — creating a safety hazard.

More importantly, chemical cleaners don't actually remove clogs — they punch a hole through them. The clog material (hair, grease, soap scum) remains on the pipe walls and the clog returns within days or weeks. You've spent money on a product that temporarily masks the problem while potentially damaging your pipes.

Enzyme-based drain cleaners are safer but only effective for organic matter (hair, grease) in mild cases — they won't touch mineral scale, tree roots, or foreign objects. They're also slow, requiring overnight treatment for any effect.

The correct approach depends on the cause: a drain snake for hair and foreign objects, hydro jetting for grease and scale, camera inspection and targeted treatment for tree roots. Our comparison of drain cleaning methods covers each approach in detail.

When to Snake vs. When to Hydro Jet

Snaking and hydro jetting are both effective drain cleaning methods — but they're appropriate for different situations. Using the wrong method wastes money and leaves the underlying problem unsolved.

Use snaking for: Hair clogs in bathroom drains, soft toilet paper clogs in toilets, foreign object retrieval, and any localized clog where the pipe walls are otherwise clean. Snaking is faster and less expensive than hydro jetting for these situations.

Use hydro jetting for: Grease buildup in kitchen drains, mineral scale coating pipe walls, tree root intrusion (combined with mechanical cutting), recurring clogs that keep coming back after snaking, and any situation where you want the pipe walls scoured clean rather than just a hole punched through the blockage.

The key distinction: snaking removes the blockage at a point; hydro jetting cleans the entire pipe. If you've had the same drain snaked more than twice in a year, hydro jetting is almost certainly the right next step. Our article on signs you need hydro jetting covers the specific indicators in detail.

Recurring Clogs: What They're Telling You

A drain that clogs repeatedly is not a coincidence — it's a symptom of an unresolved underlying cause. Here's how to interpret recurring clogs:

• Kitchen drain clogs every few months: Grease buildup on pipe walls. Snaking provides temporary relief; hydro jetting is the correct solution.
• Bathroom drain clogs every few weeks: Hair catcher not installed or not being cleaned. Install one and clean it weekly.
• Main sewer line clogs every 1–2 years: Almost certainly tree root intrusion. Camera inspection needed to confirm and assess severity.
• Multiple drains slow simultaneously: This is not individual drain clogs — it's a main line issue. The individual drains are fine; the problem is downstream of all of them.

If you're experiencing recurring clogs in Calvert County or Anne Arundel County, Deep Dive Plumbing Maryland can diagnose the root cause and provide a lasting solution. We're a woman-owned business licensed as MD Master Plumber #98433. Call (443) 440-0632 to schedule service. You can also review our guide on drain backup prevention for additional strategies.