Not far from Bassa, in Douala's PK12 district, two machines are hammering away on a corner of land wedged between buildings, making the ground shake.
Boring into the ground to reach the aquifer requires copious amounts of lubricant, in the form of water pumped in by teams at the surface and a chemical additive called Polyfor.
Care has to be taken to avoid polluting the supply, said Serge Diffo, who runs the small drilling company, Hydyam.
But, he said, "you see septic tanks right next to boreholes in residential blocks."
Cameroon's water problems are clearly big, according to anecdotal evidence, but there are few figures to give statistical depth.
The government says the public water utility Camwater serves a "majority" of households - but does not offer figures, or even an estimate.
Wells drilled for individual use do not need any prior authorization, a practice that verges on heresy in typical urban planning.
- Hygiene fear -
"Every person, in line with what he can afford, simply drills one or more wells without bothering to pay attention to anyone," said Firmin Bon, a professor of hydrology at Maroua University.
A borehole typically costs at least a million CFA francs (around $1,600) in a country where the minimum wage is 36,000 francs.
"The density can come close to 100 boreholes per square kilometer" said Bon.
"They are sometimes in contact with sources of pollution, latrines and sewage."
He predicted, at best, a rise in cases of gastroenteritis or, at worst, cholera - and, in the long term, cancer.
In the nearby but better-off valley of Logbessou, villas are fitted out as far as the eye can see with water tanks in the form of massive but unsightly black, grey or blue plastic water butts which store water from boreholes.
A study published by the Pan African Medical Journal found that in 2018, two-thirds of households in Doula's fifth district were consuming water drawn from boreholes. Half of the households were more than a 15-minute walk from a source.
The country's deputy minister for water, Hamadou Youssoufa, described the situation in Douala as "a concern," and blamed it on runaway urban development and a population explosion.
He said the ministry was carrying out a study into the hygiene of the boreholes, which "will be useful for requiring consumers to uphold the standards."
- Skepticism -
President Paul Biya, Cameroon's iron-fisted ruler for the past four decades, acknowledged in his New Year's address that the water problem in Douala was one of his "main concerns."
He said the government had been asked to launch a "mega-project" this year to supply drinking water to the city and its environs.
But Francois Songue, a 75-year-old pensioner, has grown tired of such promises over the years.
"In my part of town you have to wait for water from Camwater until two in the morning - and it doesn't come!
"I've traveled more than 10 kilometers here to get drinking water for my wife, my children and myself," he said as he stood in line at the Guinness site.
Jodelle Foguem, a young housewife, said she trusted the water that came from the brewery's taps.
"The water is not drinkable in our parts of town. We prefer to come and get it here," she said.