Knowing what not to flush down the toilet is the cheapest drain maintenance there is. Almost every blocked drain we clear in Cape Town traces back to something that went down a toilet or a sink and should not have. The items below are the ones that cause real damage, and the reason each one is a problem is worth understanding, because “it went down fine” is not the same as “it left the property”.
A blockage rarely forms where the item was flushed. It forms metres downstream, at a bend or a joint, where the item snags and everything behind it accumulates. By the time you notice a slow drain, the obstruction has usually been building for weeks.
Why it matters more in South Africa
Two local factors raise the stakes. Older suburbs across Cape Town still run clay or cast iron drain lines with joints that catch fibrous material readily, and many properties have mature trees whose roots have already found those joints. A wet wipe that would pass through new PVC will hook onto a root hair and start a blockage.
Second, properties on septic systems have no municipal sewer to absorb mistakes. Anything that does not break down stays in the tank, fills working volume, and shortens the interval between pump-outs. Chemicals are worse still, because they kill the bacteria the tank depends on.
At scale, the material that survives the sewer network congeals with fat into the masses known as fatbergs, which municipalities spend heavily to remove. The repair bill on a private property is smaller but lands on the owner: clearing a blocked line, and in the worst cases excavating and replacing a damaged section, is a cost measured in thousands of rands.
10 things you should never flush down the toilet or drain
1. Fats, oils and cooking grease
The single biggest cause of blocked drains. Hot oil pours away like water, then cools within a few metres of pipe, solidifies and coats the bore. Each subsequent wash adds a layer until the line closes. Let oil cool, pour it into a sealed container and put it in the bin. Commercial kitchens need a properly serviced grease trap rather than good intentions.
2. Wet wipes, including “flushable” ones
The word flushable describes only whether the item clears the toilet bowl. It says nothing about whether it disintegrates in the sewer, and most wipes do not, because they are held together with plastic fibres. Wipes are the most common single item we pull out of blocked residential lines. Bin them.
3. Nappies
Nappies contain a superabsorbent polymer engineered to swell to many times its dry volume. Flushing one into a drain line is close to a guaranteed blockage, and it will not break down while it waits.
4. Sanitary products
Tampons and pads are designed to expand and to stay intact when wet, which is exactly the wrong property for a drain. They also snag readily on root intrusion. Provide a lined bin in every bathroom, including guest bathrooms, and the problem largely disappears.
5. Coffee grounds and tea leaves
Fine, dense and heavy, coffee grounds do not float away. They settle in low points and bind with fat into a firm sludge that resists plunging and normal rodding. They belong in the compost heap or the bin.
6. Eggshells, bones and fruit pits
Hard fragments do not dissolve and do not break down. Eggshell in particular shatters into granules that act like grit, settling in bends and giving fat something to build on. Fit a sink strainer and empty it into the bin.
7. Starchy food waste
Rice, pasta and potato peel continue absorbing water after they go down and swell in the pipe. Potato peel is particularly bad because the starch turns gluey and cements other debris together. Scrape plates into the bin before washing.
8. Household chemicals, paint and solvents
Pesticides, fertiliser, solvents, paint and motor oil should never go into a drain. They pass through treatment works incompletely, contaminate water sources, and on a septic system they destroy the bacterial action the tank relies on. Paint additionally hardens inside the pipe. Take these to a municipal hazardous waste facility.
9. Medication
Flushing unused medicine will not block a drain, but treatment processes are not designed to remove pharmaceutical compounds and they end up in the water system. Most pharmacies accept expired medication for safe disposal at no charge.
10. Condoms, cotton wool, dental floss and hair
Grouped together because they fail the same way: none of them break down, and all of them are stringy or springy enough to tangle. Dental floss and hair in particular act as a net, binding loose debris into a solid mass. Hair is the main cause of slow shower and basin drains, and a cheap drain guard prevents almost all of it.
“Can I flush this?” – quick answers
- Can you flush tampons down the toilet? No. They are made to expand and hold together when wet, and they snag on joints and roots.
- Can you flush hair down the toilet? Avoid it. Hair does not degrade and it traps other debris. Clear brushes into the bin and fit drain guards.
- Can you flush condoms down the toilet? No. Latex does not break down and tangles with other material.
- Can you flush cotton wool or cotton buds? No. Cotton wool absorbs and clumps; buds have plastic stems that catch at bends.
- Can you flush pills or old medication? Technically yes, but do not. Return them to a pharmacy.
- Can you flush soap scraps? Small amounts are harmless, but bar soap fragments combine with hard water and fat into a solid scum. Bin them.
The reliable rule: only the three Ps belong in a toilet – pee, paper and the other one. Everything else goes in a bin.
Early signs your drain is already blocking
- Water draining more slowly than it used to, particularly if more than one fixture is affected.
- Gurgling from a basin or shower when the toilet is flushed, which indicates trapped air behind a partial obstruction.
- Persistent sewage odour indoors or around an external inspection eye.
- The toilet level rising before it drains away.
- Damp or unusually green ground along the line of the drain in dry weather.
Acting at the gurgling stage is far cheaper than acting at the overflow stage. More detail on causes and symptoms is in blocked drains 101 and five common causes of blocked drains.
If something has already gone down
Stop using the fixture, so you are not adding water to a line that cannot take it. If the item is visible and reachable, remove it by hand with gloves. A plunger is worth trying on a simple, recent obstruction.
Resist reaching for caustic drain cleaner. On a blockage caused by wipes, nappies or a foreign object it does nothing, because there is no fat for it to attack. What it does instead is sit in the pipe as a hazard for whoever opens the line next, damage older pipework, and destroy septic tank bacteria. Our guides on using drain cleaners and which chemicals are used to unblock drains cover when they are and are not appropriate.
If the blockage does not clear, or if it keeps coming back, the cause is usually further down the line and mechanical clearing is required. Repeat blockages in the same place often indicate root intrusion or a structural fault rather than anything anyone flushed, which is worth establishing before paying for a third clearing. See how to unblock a sewage drain for the steps, and the City of Cape Town residential water and sanitation pages for reporting a fault in the municipal sewer rather than on your property.
Getting it cleared
Drain Blasters has cleared blocked drains across Cape Town since 2007, using high pressure jetting and camera inspection rather than chemicals wherever possible. If a drain on your property is blocking repeatedly, see drain clearing services in Cape Town, or read about the wider consequences of leaving it in the environmental impact of poorly maintained drains.
