After living in their new apartment for half a year, a couple in Beijing began experiencing multiple health issues.
The man, surnamed Tan, and his girlfriend felt something was amiss about their rental unit when they realised the water supply was not cut off despite not paying the bill for six months.
According to Jiupai News, the couple had moved into the apartment in May, and were renting it for 10,000 yuan (S$1,900) a month.
When Tan checked the unit's water meter in November, however, he noticed that the tap water meter did not run whenever the faucet was turned on.
Instead, the numbers on the grey water meter would increase.
Treated grey water is household wastewater that can be reused for a variety of purposes such as flushing toilets, washing cars or gardening plants.
However, it is not suitable for drinking and should not be used to wash vegetables, fruits or any food item that one intends to eat. It also should not come into contact with the human body as it may cause adverse reactions.
When maintenance staff conducted investigations at Tan's apartment on Nov 22, they discovered an extra pipe which connected the toilet water pipe to the tap water pipe, reported Chinese media.
This caused the tap water in Tan's unit to be mixed with "grey water" from the toilet pipe.
The news came as a shock to the couple, who realised they had been using "grey water" every day to wash vegetables and take showers. They also drank the water.
The tenants also experienced problems such as hair loss, acne, cough and chest tightness.
Following the discovery, the couple confronted rental company Ziroom for not properly inspecting the house before leasing it out.
In a video of the confrontation, Tan's girlfriend said: "When we were renting the apartment you didn't tell me that I was using 'grey water'. If I hadn't been unwell, I wouldn't have noticed the problem."
Ziroom responded to the complaint saying that the affected pipes had been repaired, but emphasised that the issue was due to the homeowners' decision.
The tenants and Ziroom have yet to reach an agreement on compensation for the matter, Jiupai News reported.