I bought a house with a septic tank and a drywell system. The drywell has been acting up for a year and I finally found the cleanout and opened it. I measured the diameter and depth of the drywell and, using your formula, calculated the volume at 5300 gals.(10 ft. diameter by 9 ft. height). The drywell is full, the water clear, and the drywell sits in a terraced area on a hillside. 

Can your product help a system of this type? I have to assume that the problem is soil plugging. Also, what amount of your product do you recommend for a drywell of this size.

Thanks for your help.