Leaking Septic

I think our septic tank is leaking. The pipe from it might be leaking also. We worried that it was leaking before we left for holiday. When we came back, flowers were growing above the septic tank and in a line through the yard, more than they were growing elsewhere. Also, the pressure in our toilet is less than it should be. i know basic Norwegian, but do not know how to talk about specialized things like building repair. i apologize that i cannot write this på norsk. We would like for someone to come look at the problem and give us an estimate for how much it will take to fix it. Thank you.