Blocked drains are one of the most common plumbing problems homeowners deal with — and also one of the most frustrating. You clear the drain, everything seems fine, and then a few days or weeks later the water is backing up again. A persistently blocked drain is usually a sign of an underlying issue that hasn’t been properly identified or fixed. The good news is that once you understand the real causes of recurring blockages, you can take steps to prevent them and save yourself time, stress, and costly repairs in the future.

In this comprehensive guide, we’ll break down the seven most common reasons drains keep blocking, how each issue affects your plumbing system, the warning signs to look for, and what you can do to prevent the problem from returning.

1. Build-Up of Grease, Fat, Soap and Food Waste

One of the leading causes of repeated drain blockages is simple everyday build-up. Kitchen sinks are especially vulnerable because of the mixture of grease, oils, soap scum and food scraps that go down the drain daily. Even if you don’t intentionally put food waste down the sink, small particles still get washed through, and over time they accumulate inside the pipes.

Grease and fat are particularly problematic. They go down the drain as a liquid when hot, then cool and solidify further inside the pipe. As they harden, they trap food debris, soap residue and other particles, gradually narrowing the pipe until it becomes completely blocked. Bathroom basins and showers also suffer from build-up caused by hair, shampoo, conditioner, soap scum and toothpaste.

Warning signs:
– Slow-draining water
– Gurgling sounds
– Bad smells from the drain
– Water pooling around the drain opening

Prevention tips:
– Never pour grease or oil down the sink
– Use drain strainers to catch food scraps and hair
– Flush kitchen drains with hot water regularly
– Clean drains with enzyme-based cleaners

2. Hair and Soap Scum Accumulation in Bathroom Drains

Bathroom drains block repeatedly because of hair — especially long hair — combined with soap residue and product build-up. When hair washes down the drain, it becomes tangled and forms a net-like blockage that traps anything else flowing through the pipe. Soap and conditioner attach to the hair bundle and harden, forming a stubborn clog.

This is one of the most common reasons shower drains become slow over time and then fully block. A simple plunger or quick clearing may give temporary relief, but the underlying hair knot often remains further down the pipe, causing the blockage to recur.

Warning signs:
– Bad smell coming from the shower drain
– Water draining slowly while showering
– Gurgling or sucking noises after the shower turns off

Prevention tips:
– Install a mesh drain cover
– Clean hair traps weekly
– Use hot water flushes to dissolve soap scum
– Avoid excessive use of oily shampoos and conditioners

3. Foreign Objects Accidentally Entering the Drain

Another common cause of recurring blockages is something stuck inside the drain that shouldn’t be there. This is especially common in households with children, where toys, cotton buds, wipes and other bathroom items often end up in sinks or toilets.

In the toilet, non-flushable items such as wet wipes, sanitary products, baby wipes, cotton pads, ear buds and even tissues create blockages that don’t easily break down. Even items advertised as “flushable” are often not truly dissolvable and lead to frequent toilet blockages.

In sinks and showers, lost jewellery, bottle lids, toothpaste caps or small plastics can lodge deep inside the pipe. Once stuck, they trap hair, soap, fat and debris, creating an ongoing blockage problem.

Warning signs:
– Sudden, unexplained blockage
– Gurgling or bubbling noises
– Multiple drains backing up at once
– Water rising unusually high in the toilet bowl

Prevention tips:
– Only flush toilet paper — nothing else
– Keep bathroom counters clear of small items
– Tell kids not to flush toys or push objects into drains
– Install drain screens anywhere small items could fall in

4. Tree Roots Infiltrating Underground Pipes

Tree root intrusion is one of the most serious and common causes of recurring blocked drains — especially in older homes or properties with large trees nearby. Over time, small cracks or joints in your underground pipes allow moisture and nutrients to seep out into the surrounding soil. Nearby tree roots naturally grow towards this moisture, infiltrating the cracks in search of water.

Once roots enter the pipe, they expand and form a tangled network that catches everything passing through, eventually causing repeated blockages. Each time you clear the drain, it may temporarily improve, but unless the roots are removed and the pipe is repaired or relined, the problem will return.

Warning signs:
– Localised wet patches or lush green grass over pipes
– Bad smells outside
– Slow drainage throughout the home
– Gurgling noises from toilets or sinks
– Blockages that reappear often

Prevention tips:
– Avoid planting trees near sewer or stormwater lines
– Use CCTV drain inspections to identify early root growth
– Consider pipe relining if roots repeatedly enter the pipe
– Ensure drains are professionally cleared rather than DIY chemical treatments

5. Damaged, Misaligned or Collapsed Pipes

Pipes can become damaged for several reasons: age, wear and tear, soil movement, poor installation or heavy vehicles driving over underground lines. When a pipe cracks, collapses or becomes misaligned, water flow is interrupted and debris easily becomes stuck. This is a major cause of repeated blockages and one that cannot be fixed with plunging or chemical cleaners.

Older clay pipes and earthenware systems are particularly prone to cracking, allowing dirt, gravel and roots to infiltrate the drain. Even newer PVC pipes can sag or shift due to soil movement, creating “belly sections” where water pools and solids settle. Over time, these pools become severe blockages.

Warning signs:
– Frequent blockages in multiple drains
– Overflowing sewer smells
– Gurgling in toilets even when not flushing
– Sewage backing up into showers or floor drains
– Flooding outside during rain

Prevention tips:
– Get a CCTV inspection if drains block more than once
– Replace damaged sections of pipe
– Consider pipe relining to permanently fix structural issues
– Avoid parking heavy vehicles over underground pipe paths

6. Incorrect DIY Fixes or Temporary Clearing

Many homeowners attempt to fix blocked drains themselves using plungers, hot water, makeshift tools or store-bought chemical cleaners. While these might provide temporary relief, they often only clear the surface-level blockage and fail to address deeper build-up or structural issues.

Chemical drain cleaners are also dangerous — they can damage pipes, kill good bacteria, corrode joints and cause pipes to weaken over time. When drains remain partially blocked after DIY fixes, debris begins to collect again and the cycle repeats.

Improper use of drain snakes or coat hangers can puncture or scratch the pipe interior, making it even easier for future blockages to form.

Warning signs:
– Blockage keeps returning after you clear it
– Only one part of the drain seems improved
– Chemical cleaners work temporarily then fail
– Drain smells return fast

Prevention tips:
– Avoid chemical cleaners
– Use enzyme-based cleaners if needed
– Get a professional drain clearing once blockages become repetitive
– Let a licensed plumber perform CCTV inspections instead of guessing

7. Poor Drain Design or Old Plumbing Systems

Sometimes the issue isn’t what goes down the drain — it’s the drain system itself. Poor plumbing design, incorrect pipe fall (angle), improperly installed junctions, or old, narrow pipes can all cause continuous blockages. Many older homes were built with small-diameter pipes that can’t handle modern household demands.

If your home has been renovated without upgrading the plumbing system, increased water flow from new fixtures can overwhelm outdated pipes, leading to frequent clogs. Insufficient venting can also create negative pressure, slowing drainage and causing gurgling sounds.

Warning signs:
– Blockages occur across multiple drains
– Your home is older with original plumbing
– Water backs up even after professional clearing
– Drains have always been slow since moving in

Prevention tips:
– Have a plumber assess pipe sizing and fall
– Upgrade old pipes to modern standards
– Improve venting or add air admittance valves
– Reconfigure plumbing if renovations added extra load

How to Stop Recurring Drain Blockages for Good

If your drain keeps blocking, the most effective long-term solution is identifying the exact cause rather than guessing. A professional plumber can perform a CCTV drain inspection to locate the blockage, determine if it’s caused by debris, roots, a foreign object or structural issues, and recommend the right fix.

Permanent solutions include:
– Professional jet-blasting
– Root removal
– Pipe relining
– Pipe replacement
– Clearing and cleaning with specialised equipment

Addressing the root cause, rather than simply clearing the symptom, is the key to preventing blockages from coming back.

Final Thoughts

Recurring blocked drains are more than just an inconvenience — they’re a sign that something deeper is wrong with your plumbing system. Whether it’s grease build-up, hair tangles, foreign objects, tree roots, damaged pipes or a poorly designed system, identifying and addressing the underlying cause is essential. With the right combination of prevention habits and professional help, you can restore smooth, reliable drainage and avoid major plumbing emergencies.