I have built a large RWH Storage Tank (Sump) for our house in Kodaikanal, Tamil Nadu.  Water from this tank would be pumped to an overhead tank for domestic use.  The pump will be switched on and off by a Caretaker.   I am not thinking of an automatic pumping system here.  

Is it possible to install in a Mechanical Gauge so that the Caretaker can see the water level in the Sump before he switches on the pump?  The Caretaker also has to know the level to decide whether rain water has to be let into the Sump or let out (if the sump is full).

I want to avoid having to open the lid of the Sump each time we want to check the water level.   Electrical Gauge may not be the best solution here due to frequent power cuts. I will be thankful if you can guide me as to what type of gauge / equipment would suit this requirement and from where I can source it. Contact information of vendors / dealers may please be given.

V Venkatesh
vartakavi@gmail.com