I have a problem with a precast cistern that was installed in 1979 that seems to be plugged up. I removed all the dirt from the top and located the square opening to gain entry. It was about half full so I decided to be a brave soul and went in.
There was about one inch of really fine silt in the bottom and I could not find the output port anywhere along the bottom.
I am currently draining the system and hopefully when I get out all the water I may find it.
My question is, do most precast cisterns have a output port along the bottom edge?
And what would be the best formulation to disinfect the tank when the repairs, and all the silt removed is complete? I was thinking a mix of clorine and water on the way out.
I think the peoples kids I rented this property to for the last six years was the cause of the silt as I guess they used the check pipe to send stuff into the tank including some toy pieces.
Thanks to anyone who could help with this unusual problem.:rolleyes:

We don't have cisterns in my area but I did get some specs for a typical rainwater cistern. It has a 4" inlet at the top and a 1 1/4" foot valve with a 1 1/4" female threaded connection about 16" off the bottom in the end of the tank. Chorine and water would be a very good disinfectant. Good luck, Tom