Kwun Tong Town-Centre Older Buildings Drain Services

According to a HK01 report of 1 February 2020, in an older building of more than 50 years in Kwun Tong town centre, a first-floor flat had sewage backing up out of the toilet for three days in a row and spilling into the corridor on that floor. The report quotes the resident as saying that after she asked the Drainage Services Department for help, staff checked the manhole outside the building, found nothing blocking the drain and therefore judged that the building's own pipes were blocked, advising her to engage a drain company; the management company told the paper it had sent a drain company on the first day and that the burst had since been resolved. The same report quotes the architect Kwan Siu-lun as saying that burst soil pipes often occur in tong lau and older buildings, and that pipes on low floors bear the most pressure, so the problem is common in low-floor flats. The order of steps is worth remembering: first establish whether the problem is the flat's branch pipe, the building's stack or the street drain, and only then decide whom to call. Where sewage has reached a corridor or rear lane, the area also needs cleaning and disinfecting after the drain is cleared.

The Buildings Department says drainage systems in buildings of every type and age develop defects of various kinds and degrees, the common examples being leaking or broken external drainage pipes, rusty internal pipes and unauthorised alterations to the drainage system. As an inference from building age, blocks completed between 1963 and 1972 were normally built with cast-iron or steel pipes, and after half a century thinning walls, weeping joints and rusted, loose brackets are all common. The HK01 report of 2020 also quotes an architect saying that older buildings generally use metal pipes such as iron drains, and that clearing them improperly — with a high-pressure jet, or by overusing chemical drain cleaner — can corrode the iron and open a hole. The Environmental Protection Department adds that buildings completed before the mid-1980s may contain asbestos cement sewage pipes, which cannot be identified by appearance or colour, so suspect material should be treated as asbestos-containing — and not cut or drilled — until a registered asbestos consultant has confirmed what it is. Pipe material and condition therefore have to be established first, and the tool and pressure chosen to match.

The Drainage Services Department's list of locations prone to blockage has seven entries in Kwun Tong, two of which — Kwun Tong Road near Hong Ning Road, and Tsui Ping Road between Kai Lim Road and Kwun Tong Road — sit on the edge of this cluster of older buildings. The department explains that such locations are identified from past records and observations of frequent flooding in heavy rain caused by leaves, silt or refuse blocking the inlets. The whole of Hong Ning Road is on a slope, so given the terrain rainwater concentrates towards Kwun Tong Road; once the street drains are full the building's private drain has nowhere to discharge, and what comes up first is usually the shops at the foot of the slope, followed by the toilets and bathroom floor drains in the low-floor flats. Wikipedia's account of the September 2023 rainstorm records that the Observatory issued that year's first Black Rainstorm Warning at 11.05pm on 7 September 2023, after districts including Kwun Tong recorded more than 70 mm of rain in an hour. In rain like that, clearing gullies and manholes before the wet season and having flood boards or sandbags ready matters a great deal.

In a statement of 12 February 2020 the Buildings Department said owners altering a drainage system, including anti-syphonage pipes, must appoint a contractor registered under the Buildings Ordinance through the Minor Works Control System, and that every sanitary fitment — water closet, wash basin, bathtub — must have an effective water seal. The statement says expressly that these requirements also apply to drain pipes erected or altered when a flat is subdivided, and that the department would step up site audits of in-flat drainage alterations. As an inference from building age, most flats here have been renovated more than once: bathtubs replaced by shower trays, a washing-machine outlet added, kitchens and bathrooms moved, so trap types and connection points often differ from the original plans. If the smell or the slow draining started after a renovation, begin with the traps, the anti-syphonage pipe and the connection of any new outlet.

URA records show that Park Metropolitan in Development Area 1 of the Kwun Tong Town Centre project was completed in July 2014 and Grand Central in Development Areas 2 and 3 in April 2021, while Development Areas 4 and 5 are carrying out underground utility diversion works, with the revised draft plan approved by the Chief Executive in Council in September 2024. Given the nature of such works, the buildings still standing may meet rear lanes and streets closed in stages, drain inlets moved, or temporary street connections, so in heavy rain the drainage route differs from before. If the same point keeps silting up, a CCTV drain inspection is worth doing to confirm where the pipes actually run before deciding between desilting and correcting a connection. When booking a visit, please say which street a vehicle can park on and whether the manhole is inside a closed-off area.