Does financial participation in the repair of a water pump count as an ongoing charity (Sadaqah Jariyah) that benefits one after death, especially if the participant knows nothing about it beyond their financial contribution?

Perpetual charity (Sadaqah (definition) Jariyah) is that whose reward continues for the donor after their death. An example of this is waqf (endowment), where the principal is held inalienable and its usufruct is dedicated. Repairing and equipping a water pump is considered perpetual charity, like digging wells and channeling rivers. Participation in it is permissible, and it is not a condition for the donor to perform the act of charity themselves; rather, representation (by an agent) is permissible.