I know what you're thinking. I can't use them to chlorinate a pool consistently, and you would be correct. This thread is actually for an aerobic septic tank. The septic tank installer said to simply use the standard pool pucks in the septic tank. I have read online that the tabs should only be cal-hypo as when the water is discharged onto the "lawn" (in this case lawn means field of weeds far from the house) the stabilized chlorine will not be broken down by the sun and remain there killing the "grass" (weeds). Cannot seem to find a local place that sells cal-hypo tabs and they seem relatively expensive, would it be that big of a deal to use the tri-chlor is I don't care about the area the water is being sprayed onto?