Cockroaches and tiny dark insects crawling out of your kitchen sink or bathroom floor drain are almost always travelling up through the pipe itself, not squeezing in through walls or tile gaps. In older Sanur villas this is especially common because many P-traps dry out over a few days, rubber seals crack, or open connections run straight to a septic line. The good news is that you can usually stop the problem with a handful of practical fixes you can start today.
Where Do They Actually Come From?
Cockroaches (especially the small brown variety common in Bali) are excellent swimmers and will navigate flooded pipe networks looking for moisture and food. Once they find an open vertical shaft — your drain — they simply climb up and out. You do not have a 'roach infestation' in the room; you have a one-way highway into it.
In Sanur the situation is amplified by a few local factors. Humidity stays high year-round, so roaches are active even in the dry season. During the rainy months (roughly November to March) water levels in shared sewer lines rise, pushing insects upward. Older villas built before modern plumbing codes often have no proper trap at all on floor drains, or the trap was installed with a thin plastic sleeve that has since disintegrated.
Check Your Water Seal (P-Trap)
A P-trap is the U-shaped bend under a sink or the bottle-style trap under a floor drain. When it holds water, that water column blocks gas and insects from rising. If the villa sits empty for a weekend, or if a bathroom is rarely used, the water evaporates and the seal disappears overnight.
Here is what to do: run cold water into every drain in the house for a full minute, then look underneath. For a sink, lift the access panel and confirm the U-bend is filled. For a floor drain, remove the cap and check whether there is standing water in the trap below. If the trap is bone-dry, fill it now. If the rubber gasket inside looks cracked, flattened, or covered in black mould, replace it — these are inexpensive parts available at any hardware shop in Sanur or Legian.
If your villa uses well water rather than PDAM mains, mineral buildup can coat the inside of traps and reduce their effective depth. A quick descale with white vinegar poured down the drain once a month helps keep the seal functional.
If you are still seeing insects after checking your traps, send a clear photo of the affected drain on WhatsApp and I will tell you exactly what part needs replacing before booking a visit.
Add Mesh Screens and Drain Covers
Even with a healthy P-trap, small insects like drain flies (those fuzzy grey moths) can crawl through a thin film of water. The simplest barrier is a silicone mesh cover that sits over the drain opening. They cost very little, fit standard 40 mm and 50 mm floor drains, and you can buy them at most Bali supermarkets or order online.
For kitchen sinks, a fine stainless-steel hair-catcher screen does double duty: it stops food particles from building up (which attracts roaches) and blocks the smallest insects. Clean the screen weekly during the wet season when organic matter decomposes faster in the heat.
- Silicone mesh covers for bathroom and outdoor floor drains
- Stainless-steel sink strainers for kitchens
- Replace any torn or warped screens immediately — a gap wider than 1 mm lets roach nymphs through
Safe Chemical and Mechanical Treatments
Before reaching for a bottle, try the mechanical route first. Pour two litres of boiling water down the affected drain, wait ten minutes, then follow with a cup of baking soda and half a cup of white vinegar. Let it fizz for twenty minutes and flush again. This clears grease and biofilm without harsh fumes.
If the blockage is stubborn, an enzymatic drain cleaner (look for products containing Bacillus bacteria) will break down organic matter over 48 hours and is safe for septic systems. Avoid pouring caustic sodium-hydroxide 'drain unblockers' into old villa pipes; they can soften PVC joints and, worse, react unpredictably if another chemical is already sitting in the line.
Important safety note: never mix bleach with any other cleaning product, especially near open drains where vapour pools at ankle height. If you smell gas or notice a strong sulphur odour from the floor drain, stop using that fixture and call a licensed plumber to inspect the vent stack.
Ongoing Prevention Through the Year
Make a simple monthly habit: run every drain in the house — kitchen sink, bathroom basins, shower, outdoor tap, washing-machine outlet — for one full minute so no trap dries out. In Sanur's dry season this takes under five minutes and prevents most roach traffic before it starts.
During the rainy months, check your floor-drain traps after heavy storms. Shared sewer lines can back up slightly, and a weak seal lets insects ride the surge upward. Top up the water level and wipe away any standing film around the cap.
If your villa has an external septic tank (common in older Sanur properties), make sure the inspection lid is sealed and the overflow pipe is not cracked. A small gap there becomes a direct entry point for roaches heading toward your ground-floor drains. A quick visual walk-around each month catches problems early.
Questions
Will sealing the drain with silicone or epoxy fix the problem permanently?
No. Sealing a drain shut blocks water flow and will cause flooding when you use the fixture. The correct fix is restoring the P-trap water seal and adding a mesh screen on top. If the trap body itself is cracked or missing, it needs to be replaced by a plumber rather than glued over.
Are the tiny black bugs from my shower drain cockroaches or something else?
They are most likely drain flies (Psychodidae) or small moth larvae, not true cockroaches. They look similar at first glance but have two wings and fuzzy bodies. The treatment is the same: restore the water seal, clean biofilm out of the pipe, and add a mesh cover.
Can PDAM water pressure damage my traps and let insects in?
High-pressure surges from the PDAM network can dislodge a loose rubber gasket inside a bottle trap, creating a gap that roaches exploit. If you notice the problem appearing after a water-works maintenance day, check the gasket seating and re-tighten the trap nut. A worn gasket should be swapped out.
I'll reply with what's needed, a price and when I can come.
