cistern leak repair

[Code54]

I noticed that at the house I recently purchased the cistern seems to be leaking. Not really bad but enough to make a 1 foot wide 10 foot long wet spot in the yard. I do not use the cistern for the house water (we now have city water) but it is used for all the outdoor water needs (washing cars, watering plants, cleaning the tractor...)
Anyway - how would I go about repairing the leaks. I dug out around it today and found 2 small cracks and a little hole that would pee water . I am guessing I need to empty it down below the level where it is leaking then patch it somehow. Is this correct and how do I patch it and with what? Thank you for any info, I have no clue on this one.
Thanks!!!

 

[Egon]

What is the tank made of?

Egon

 

[Code54]

Sorry about that - it is made of cement block.
Thanks

 

[milkman]

I've used this stuff and it really works. I've ordered from this place also, though not ordered water plug from them. It's easy to use and easy to follow directions. Water Plug Should have made it clear, I have ordered pool supplies from them and used water plug that I purchased elsewhere, didn't want you to think that I had used the epoxy shown with the water plug.