That is until she and her 7-year-old son got cholera, in an outbreak that is sweeping the country.
They fell badly ill last week, joining more than 10,000 people infected by the disease.
Both have now recovered.
"We didn't know that there was an outbreak of the disease, but now we know. We never used to chlorinate, and we were just using directly from the tank and there was no proper care."
Nyendwa said she was in such a bad condition, she didn't think she'd leave the hospital alive.
Indeed, at least 432 people have died since October, according to government figures.
Cholera is spread through contaminated food or water, typically in crowded environments where people lack access to clean water and sanitation.
Serious cases can cause acute diarrhea and, if untreated, death.
Doctor Tamara Lungu said the key to tackling the disease is rehydration.
"So what we need urgently is the rehydration fluids and also the antibiotics to help with this bacterial infection, as well as deworming the patients because some patients have got worm infestation as well."
Nine out of Zambia's ten provinces have reported cholera cases.
The vast majority, though, are in Lusaka - a city of some 3 million people.
Authorities there have set up a makeshift treatment center outside the National Heroes Stadium.
During a visit, Health Minister Sylvia Masebo said Zambia has been forced to mobilize retired health workers and volunteers to help.
Neighboring countries Zimbabwe, Malawi and Mozambique have also been battling cholera since last year as outbreaks surged worldwide and vaccines ran out.
