If the water is coming out of the tank, then the drainfield is almost certainly flooded and not absorbing water. The first thing ot do is to have the septic tank pumped and watch to see if water flows back into the tank from the drainfield. This is also an indication that the drainfield is flooded. 

If the field is flooded, then it needs to be dewatered before it can be treated. If you have no access, then I would have the pumper install a riser between the septic tank and the drainfield. This gives you a place to add the Septic-Scrub and also a place to monitor the drainfield in the future. 

If you have any questions, please do not hesitate to call and discuss your situation.