Shower Leaking? Fix Tray, Joints & Drain Before Damage Spreads

A slow drip under your shower tray that you keep mopping up will quietly rot the subfloor, lift tiles, and feed mould into the wall cavity within a few rainy-season months. In most Sanur villas the culprit is one of three things: perished silicone at the tray-to-wall joint, a failed gasket on the drain (trap), or a floor slope that simply does not push water toward the drain. The good news is that all three are visible, checkable, and fixable without tearing up the whole bathroom.

Where Does the Water Actually Go?

Before you buy anything, trace the wet spot. Run the shower for two minutes with the tap fully open, then turn it off and watch. If the damp patch appears along the back wall base, the leak is almost certainly the silicone joint between tray and tile. If the wetness shows up directly around the drain flange, suspect the trap gasket. If water pools in one corner and slowly seeps under the tray lip, the problem is gradient – the floor is not sloping toward the drain.

In older Sanur villas the subfloor is often a bare concrete slab with a thin screed layer. Once water gets past the tray edge it wicks sideways through that screed and can travel well beyond the visible stain before you notice a dark ring on the ceiling below. During the dry season the slab dries out and hides the damage; by the time the November rains arrive the moisture has already reached the joists or the lower brickwork.

• Wipe the area completely dry, run the shower, and mark where new damp first appears.
• Check the underside of the vanity or the ceiling in the room below for early staining.
• If you smell musty mould but see no visible drip, lift a corner tile near the tray to inspect the substrate.

Silicone and Joint Seals

Bali's combination of salt-laden sea air, strong UV, and high humidity ages bathroom silicone far faster than in a temperate climate. The flexible sealant that once looked smooth turns chalky, cracks along its length, and eventually pulls away from the tile face. A hairline gap at the back-wall joint is enough to channel a steady film of water behind the tiles every time you shower.

To re-seal properly: scrape all old silicone out with a plastic scraper (not a knife – you will nick the tile glaze), let the joint dry for 24 hours, then apply a fresh bead of mould-resistant sanitary silicone. Press it into the corner with a wet finger for a clean concave profile. Keep the shower dry for at least 48 hours before using it again.

A quick safety note: if your outlet or light switch sits within arm's reach of the work area, isolate the circuit at the DB board first. Water plus live electrics is not a risk worth taking, even for a two-minute job.

• Inspect joints every six months; in open-air showers check monthly during the rainy season.
• Use a dedicated sanitary/mould-inhibitor silicone, not general-purpose sealant.
• If the silicone keeps failing within weeks, the underlying surface may be damp – fix the source leak first.

The Drain (Trap) and Siphon

The trap – that little U-bend under the drain cover – does two jobs: it lets water flow away while holding a small pool of water that blocks sewer gas from rising into your bathroom. In many Sanur villas built in the 1990s and early 2000s the connection between the tray outlet and the waste pipe is held by a single rubber washer or a short length of flexible hose. That rubber perishes in the heat and starts weeping after three to five years.

To check: remove the drain cover, look down the outlet pipe with a torch, and feel around the flange where it meets the tray. If you see a dark ring of old gasket material or a soft, squishy washer, replace it. A new EPDM or butyl washer costs very little and takes ten minutes to fit. While you are in there, run a cup of water through the trap to confirm the seal holds and the flow is not sluggish.

If the drain also smells of sewage, the trap seal has dried out or the siphon is cracked. Pour a litre of water down the drain every few days during long dry spells to keep the seal topped up.

• Replace the trap washer at least every four years as a preventive measure.
• Make sure the waste pipe under the tray slopes away from the wall – even a slight upward kink will back-pressure water into the joint.
• Never use chemical drain openers on an older PVC or ABS pipe; they can soften the joints and create a new leak path.

Floor Slope and Gradient

A shower floor should fall roughly 1–2 cm toward the drain across its full width. In practice many villa bathrooms were tiled flat because the screed was poured level before tiling. The result: water sits in a shallow pool around the tray edge for several seconds after each shower, and that standing water finds any microscopic gap in the silicone or under the tray lip.

You can test the slope with a spirit level laid across the floor from the drain outward. If the reading shows zero or negative gradient (i.e., the far end is higher), you have a design issue rather than a materials failure. Options range from re-grouting with a slightly thicker bed to lift the outer tiles by a millimetre or two, to installing a small linear drain along the back wall so water has somewhere to go even if the main trap is slow.

During the rainy season this matters more: rain dripping off the roof eaves onto an open-air shower adds volume that a marginal gradient simply cannot handle quickly enough.

• Check gradient with a 60 cm level; aim for at least 1 % fall toward the drain.
• If the slope is wrong but the leak is minor, a well-fitted linear drain along one side can relieve the pressure on the central trap.
• Avoid 'fixing' the slope by adding thick adhesive under individual tiles – it creates lipping and trips.

Open-Air Bathrooms: Why They Leak Differently

A large share of Sanur villas have no glass screen or curtain around the shower – just a tiled floor, a tray, and the sky above. That is lovely in the dry season, but it changes the failure pattern in three ways. First, sea breeze dries the silicone joints unevenly, so one corner cracks while the opposite side still looks fine. Second, monsoon rain hits the tray directly, doubling the water load your trap must clear in a given minute. Third, splashing reaches the adjacent deck, garden wall, or bedroom threshold, so a small joint weep that would be invisible behind a glass panel becomes a visible damp streak on the teak decking outside.

Practical adjustments for open-air showers: fit a slightly larger-diameter trap (80 mm instead of 50 mm) if the original plumbing allows; add an overflow channel or scupper at the lowest point of the surrounding deck; and re-seal all exposed joints with a UV-stable silicone rated for exterior use. Check these seals after every heavy storm week rather than waiting six months.

• Use exterior-grade, UV-stable silicone on any joint exposed to direct sun.
• Make sure the deck or tile surround slopes away from the shower area, not toward it.
• After a prolonged downpour, walk around the shower perimeter and look for new damp patches you have not seen before.

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