Luk Yeung Sun Chuen Drain Services

It follows from the structure that sewage from all 17 blocks turns into horizontal pipes at podium level before being led out past the depot. Once such a run is narrowed by grease, wet wipes or renovation debris, the first symptoms usually appear not on the upper floors but on the few floors closest to the podium: the water level in the toilet rises and the floor drain bubbles, especially at the busiest morning and evening times for water use. Another sign is staining on a podium, lobby or mall ceiling. If only one outlet is slow, the flat's branch pipe is the usual cause; if several flats in the same block are affected at once, tell the management office straight away and photograph the spot and the time so the podium-level check can be arranged.

Luk Yeung Galleria is a base mall of 170,000 sq ft; the 2007–08 refurbishment took the shop count from 63 to 85 and more than doubled the number of restaurants. The Environmental Protection Department's grease-trap maintenance guidance advises inspecting a trap at least every three days, cleaning it once greasy waste occupies the top 30 per cent of the liquid depth, and recording each clean in a log book. For a shop tenant, a slow sink or kitchen floor drain usually means grease has built up. For a resident, a drain smell around the podium, a back alley or the mall, or cockroaches and drain flies there, is normally for the mall side to follow up: pass it to the management office rather than dealing with shared pipes yourself.

The estate's external walls are finished in white and brown mosaic tiling; as an inference from the design of this generation, soil pipes, vent pipes and their brackets are usually run on the elevations or in the light wells. APP-133 notes that cast iron pipes in some existing buildings rust and leak prematurely, and that their fixing supports corrode too. As a general inference from building age, external pipes in their forties may show rust staining, weeping joints or loose brackets; inside the flat the clues are a smell near a window or light well that comes and goes, damp patches on a wall, or drips under a pipe. The Mandatory Building Inspection Scheme's list of prescribed items covers both the drainage system and external wall tiling, so external pipes are a common-parts inspection matter: report what you see to the management office rather than erecting scaffolding or altering pipes yourself.

As an inference from the design, the toilet, basin and bathroom floor drain in the same flat position most likely share one stack running from the top floor down to podium level. The Buildings Department explains that when an upper flat discharges a large volume at once, syphonage creates negative pressure in the branch pipes below, enough to suck out the water held in a trap, which is why an anti-syphonage pipe must extend to more than a metre above the roof to balance the pressure. If the water in your toilet drops for no reason, or the basin and floor drain make a sucking noise when a neighbour drains water and a smell follows, check whether the anti-syphonage pipe has been removed during renovation or blocked. The other half of the story is much simpler: in a rarely used bathroom or a vacant flat, the water seal evaporates. The Buildings Department's advice is to top up every floor drain at least once a week with about half a litre of water; if the smell survives two or three weeks of that, the trap may be cracked or may have been swapped for a shallow-seal type.

The podium garden is open to the public, footbridges link it to the transport interchange and nearby malls, and the mall itself sits next to Exit C of Tsuen Wan station, so it sees more people and more fallen leaves than an enclosed podium would. The Drainage Services Department says most recent flooding cases are not caused by insufficient drainage capacity but by other factors; its own list of locations prone to blockage is drawn up for places that flood repeatedly because leaves, silt or refuse block an inlet during a rainstorm. That is why podium and light-well rainwater inlets need clearing regularly. As district background, the Tsuen Wan Drainage Tunnel opened on 28 March 2013, runs 5.1 km with intakes at Wo Yi Hop, Lo Wai and Tso Kung Tam, operates only when an Amber rainstorm warning or above is in force, and mainly intercepts hillside runoff, while surface water in the town centre still relies on underground drains. That is background about Tsuen Wan and says nothing about this estate in particular. If water ponds on the podium during heavy rain, photograph the spot and the time for the management office, and when cleaning, keep leaves and litter out of the rainwater inlets.