Fats and oils from surrounding restaurants had mixed with water and foreign matter inside the pipes, congealing into one of the biggest "fatbergs" he'd ever seen. The mass of fatty waste clung to the walls of the underground system, constricting the thoroughfare, bringing what was flushed down back up.

These days, Mr Allen is more often in the plant than on the street dealing with "generally liquid", which still has the potential to overflow from Canberra's manholes. Access points which are built into our streets every 100 metres or so to allow people like Rob to get in and high-pressure hose blast or manually dig out the dirt and doo-doo accumulating in the sewerage system below.

Since Canberra began experiencing coronavirus panic-buying, manpower and machinery requirements are expected to increase as shelves are cleared of a basic necessity.

Toilet paper, designed to break down in water, has been replaced in some households with wet wipes. Confused Canberrans have since increased calls to ACT sewerage operator Icon Water to find out what goes down.

"Pee, poop and paper," operations manager Mr Allen said. "With (toilet) paper in brackets."

Canberra toilets are connected through 2300 kilometres of pipes, through which the "three p's" are supposed to travel to the ACT's main wastewater treatment plant in Holt. A giant sieve fishes out foreign matter to be burnt or buried. What remains is treated through a process which includes chemical and biological filtering, before being discharged into the Molonglo River.

Toilet paper is designed to break down in less than a minute, and tissues in about four weeks - whereas wet wipes have been found intact in compostable toilets years after being discarded. Mr Allen said they present the biggest problem to Canberra's sewerage system, not just at the main plant, but in residential backyards too.

"The pipe system underneath your house, that belongs to the owner - if you put wet wipes down the toilet you risk clogging it up. It can lead to a very expensive fix for a homeowner," he said.

In addition to being a waste of time, fixing waste build-ups is a waste of resources.

Mr Allen said more than a million dollars is spent each year to fix blockages in Canberra, time and money which would otherwise be directed towards finding solutions to an increasing demand for water and increased pressure on the catchments as the population grows. With climate change and extreme weather, events such as bushfires, floods and droughts are also changing inflows to water storage and sending sedimentation and erosion into the water network.

"Just because you can flush it - it doesn't mean you should. The standard wet wipe is not meant for the sewer," he said.

Nappies, tissues, tampons and ... people's underwear ... also regularly cause problems, Mr Allen said.

"People think if it flushes down, the problem goes away. That's not strictly true - it may not be a problem for you."

The flushability of "flushable wipes" has come into question recently, with Kimberly-Clark in hot water for using "flushable" on its label.

The Australian Competition and Consumer Commission launched proceedings against the maker of Kleenex tissues, Huggies nappies and Viva paper towels in the Federal Court in 2016, alleging its marketing of Kleenex Cottonelle Flushable Cleansing Cloths as "flushable" was false or misleading.

The ACCC also alleged that Kimberly-Clark advertised that these products were made in Australia, when that was not the case.

In June last year, the ACCC's case was dismissed, with the exception of the representation the wipes were Made in Australia, which the parties agreed was false or misleading.

With the support of Sydney Water, the ACCC appealed the dismissal in February this year. It is still awaiting an outcome.

Sydney Water has estimated it spends more than $8 million a year manually removing "fatbergs" or masses of wipes from sewerage pipes. The cost across Australia is estimated to be more than $15 million a year.

Mr Allen said Canberra has avoided the fatberg carnage experienced in the likes of London, which has had concrete caught up in its 250-metre monster bergs, largely due to population and a younger system.

He said the hand-built sewers of yesteryear lent themselves to large underground intersections, with lots of opportunity for waste to build up and clog the systems.