Rachel Wanjiru was already struggling to get enough water to wash her children's hands during the coronavirus lockdown - then a landslide knocked out the supply near her home in Nairobi's Kangemi slum.

Heavy rains swept away the main water pipes running through forests in the Aberdare mountain range north of Kenya's capital a week ago. Soon after that, the Nairobi Water and Sewerage Company shut down a treatment plant feeding the city.

Now huge swathes of Nairobi, from its slums to its well-heeled districts of Lavington and Kitisuru are struggling with little to no supplies, at a time when the government is ordering people to stay put and keep clean.

"Will we deal with water shortage or the coronavirus? How can we survive without water when we are being told to wash our hands?" asked Wanjiru, a mother-of-two who also needs water to wash the vegetables she sells on her stall.

Before the landslide, she went to a better-off neighbour's house and paid them five shillings (five US cents) to fill a 20 litre jerry can of water from their pipe.

Now that is gone, she has to trek an hour away to buy the same amount of water from a private borehole owner at four times the price. Others are relying on bowsers and trucks.

Nairobi's water infrastructure was already creaking. At the best of times, Nairobi Water and Sewerage Company could only supply 526 000 cubic metres out of a daily demand for 810 000, according to Nahashon Muguna, the utility's acting head.

Since the landslide, supplies are down another 20%, Muguna told Reuters. "We have mobilised a contractor to do the repairs," he said. Normal supplies should resume in the next two weeks, he added.

That is too long for human rights activist Boniface Mwangi, who has called on the government to make the supply of water free during the Covid-19 crisis.

"For a city that is under lockdown due to the pandemic, there should be water in the tap. There should be no excuse," he said.