Replacing a poorly maintained tankless
It always happens…
The idea was pretty simple. It was time to have a 12-year-old Bradford White tankless water heater serviced. Maintenance was, as the homeowner said, “a little sketchy” during the heater’s life, and this, coupled with hard Southern California water, had proved a deadly combination. So it wasn’t too surprising when an inspection revealed the trusty old heater was on its last legs after only about half of its service life had passed. There was no choice but to go for a replacement.
Mike Henderson, a field supervisor with A-1 Total Service Plumbing of Los Angeles, pointed out several leaky spots inside the Bradford White once he had disconnected the gas, electricity and water, and removed the cover to perform a regular service. The area’s ultra-hard water and marginal maintenance practices had brought about its untimely death at about the midpoint of its designed useful life. It was still working fine, but there was corrosion on the hot water outlet, indicative of a slow leak over time. Also corroded was the water inlet and the O-rings from the heat exchanger were leaking from the bypass servo. All were small leaks over a long period of time, but Henderson said flushing out the scale could make the leaks worse, thus the replacement was called for. [Check out the April, 2006 edition of RJ to see this Bradford-White heater being installed brand new by Saddleback Plumbing.—Ed.]
POTENTIAL DIFFICULTY SCALE:
The first step was to remove the old heater from the wall. This was accomplished with a wrench and a little horsepower from Henderson. “We need to clear the canvas, so to speak,” he says. He measured the unistrut to make sure its spacing on the wall would be copacetic with mounting the new heater, a Noritz condensing NR711DV.
The next step was to put the new heater up on the wall. That’s the easy part. “It’s like throwing the backbone of the project on the wall,” Henderson says. Luckily the existing unistrut was installed in a way that made installing the new Noritz easy — it bolted right up. The more difficult part of the job is to match up existing plumbing, which was tailored for the Bradford White Everhot, and make it fit the Noritz, and to do so in a sanitary manner. The water and gas inlets, and water outlet were close to matching up, but Henderson had to do some custom work to get everything installed cleanly.
The first step in matching the new heater with existing plumbing was to modify the vent so the unit will exhaust properly. The old, “tube-within-a-tube” venting with combined intake/exhaust capability was removed and replaced with 3-inch PVC venting, which can be used by the newer, condensing unit.
The existing 1/2-inch gas valve that came in the box with the old heater was replaced with a full 3/4-inch full port ball valve made by F&W to feed the new unit properly. He installed a flex connector from Brasscraft to connect the gas line. The threads were coated with Hercules’ Megaloc thread sealant to ensure a leak-free seal. The reason we could use the flex line is this house has a sediment and moisture trap at the gas meter. Otherwise hard lines should be used.
Next was to begin working on the water inlet and outlet. He installed new Matsui isolation valves. Then he “got Neanderthal” with a reciprocating saw to trim the copper water inlet and outlet. From there it was a cut-and-measure-and-sweat proposition to get the inlets, the new isolation valves and a pressure relief valve installed in the new configuration required by the new Noritz. And, Henderson notes, this condensing heater will require a condensate line to be installed as the last plumbing step.
Once it was plumbed, he turned on the water supply and checked his work for leaks. When that was done, he installed the gas and electricity lines, and the pressure relief valve. Then he pulled the front cover and installed the electrical pigtail. A condensate line was connected to the washing machine standpipe to get rid of the combustion byproducts created by a condensing water heater. Henderson says this model Noritz requires a remote control unit to bring the set temperature on this heater above 120° F. Henderson installed the remote by sticking it to the side of the heater and running the wires inside the case to their connection points. This one was set at 130°.