In June 1888, the firm of "J Monier constructeur" was declared bankrupt, and in April 1889 went into liquidation. However, in 1890 he formed a new firm: "L'Entreprise générale de travaux en ciment J Monier". In 1891 came yet another application for a patent: for conduits for telephone and electricity cables. About this time Monier built his last-known project, a service reservoir for an Old People's Home at Clamart, donated by Marie de Ferrari, duchesse de Galliera (global coordinates 48.79756, 2.261623). The reservoir structure is 10 metres high and 8 metres in diameter. The floor of the tank is 8 cm thick, and the roof 5 cm thick. The exterior decoration was designed by architect Prosper Bobin in a neo-classical style. The reservoir is still extant (2010). After this, it seems that Joseph was at least semi-retired, living with his three elderly sisters and his second wife.