after replacing a leaking pipe adapter on a Navien cr-180 tankless unit today, i decided to take some CO readings at the termination. With the kitchen tap running only, I got a CO reading of 115 PPM. Firing rate was about, 110,000 btu's. My own Rinnai tankless unit with the bathroom tap running, produced 55PPM and firing at about 90, 000 Btu's. Should there be any concern regarding these readings, or are they fairly normal. Gas piping is all to code. Any areas to look over again??