In a word, excellent. Our Noritz tankless water heater stopped heating, plus we had gone 9 years without a descaling, so we had 2 tasks. I selected Stanley Plumbing because their website prominently indicated they do tankless water heaters, and are also specifically mentioned they are a Noritz installer. Don Stanley came out promptly. He cautioned me that if an old water heater that has never been descaled, and you have hard water (we do), sometimes descaling can essentially unplug an existing a leak. In other words, sometimes a tiny hole is actually plugged by the scale. I agreed and he went to work. First he fixed the "not heating" problem ? the ignitor was corroded, so he replaced it. Then, he descaled the water heater, and it did spring a small leak. Fortunately, he noticed our water heater was still under the Noritz factory warranty. He called Noriz, and they rushed out the parts the next day. (We are fairly close to the warehouse.) The parts were free under warranty, though labor was not, but his rate was reasonable. Don returned to replace the leaking heat exchanger. When he removed the old one, it was obvious there had been a slow leak for a long time ? there was a stream of corrosion running inside, right down on to the ignitor, which is why the old igniter failed in the first place. Both Stanley Plumbing and Noritz have my full endorsement. Don Stanley for his good service and reasonable prices, and Noritz for standing behind their very good product. When someday my water heater finally dies, many years from now, I expect to call Stanley Plumbing and asking them to install a new Nortiz.