I have a 9’ x 3’ x 5’ deep, (1000 gals), concrete septic tank with a leaking joint halfway up the depth. I’d like to go in after having it pumped out, wire brush and hose off the gunk in the joint and reseal it with hydraulic cement. I’m wondering if it would help to cut a negative slot with a grinder to help the bond. I intend to use a forced air system and hoist and harness for safety. Any thoughts are greatly appreciated.