Instruction: Output yes if the supporting document can answer the given question. Otherwise, output no.

Input:
Question: What size gas line is needed, how far from the gas meter can it be and can I use flex gas pipe or galvanized pipe?
Document: But when this unit comes on, I can hear the fan and burners kick on, reminding me of my gas use. Also I would like to call this or a tank water heater what it is. A water heater not a hot water heater. If you already have hot water you dont need this.
This is a good unit, great for showering or bathing. My only concern is that at times when I am washing my hands or some other minor use of hot water,  I hear the unit kicking on burning the gas that I am paying for while I wait for the hot water to reach the faucet. Most of the time I am finished with my job before the water reaches the faucet. Of course the same thing was happening when I had a tank.
I waited to write my review until I received the updated gas bill. Things on that side seem good. We're saving money. We can take as many showers in a row as needed. Also good. As another reviewer said you can hear the fan running. This can be a positive or negative I guess. On the positive you are aware that you are using gas with the sound. On the negative the sound is kind of a drone that could get annoying.
Well let me explain.I installed the unit myself. I do not recommend that unless you are very comfortable with your DIY skills. If in doubt don't! It took me a whole day to complete. If you do decide to do it yourself then you need to be aware of some things. I found the PVC and gas piping I needed to complete the install at my local Lowes and Home Depot stores. Their employees claimed no knowledge of tankless water heater installation procedures or requirements, probably to avoid any liability.
Rheem technical support was outstanding, however. I also ordered the brass valve kit, RTG20220AB, for future flushing of the heater, and the concentric vent kit, SP20245. You may use/require a different vent kit. If you use the SP20245 then do not use the enclosed instructions, always refer to the use and care manual that comes with the heater. In my case, both sets of instructions contained erroneous info.
I have had this heater installed for about a month now. It has done exactly what it is supposed to do. I replaced a 50 gallon gas tank water heater that was 17 years old. I raised three girls on that old tank, boy how I wish I had had this one instead! I can now take a shower right after one of my girls gets out and not worry about running out of hot water.
I called back and asked again just to be sure. I was again told the same thing by another agent. Make sure you also install the condensate trap on the intake air side of the vent. Maybe by the time you are purchasing yours Rheem will have updated their instructions. However, if you are unsure don't hesitate to call tech support. I hope this helps you!I highly recommend this heater!
I did not install our unit so I can't say that it is or is not easy to install however the crew (2 guys) that installed mine took at least 4 hours. Overall I would recommend this unit. It IS expensive however with tax credits, it became much more reasonable. If I were to build a new home I would not hesitate to install one of these.
If you are installing the vent vertically, then you are told to install the elbow and to add a connector and another elbow that are not supplied with the unit. The included elbow does not fit the top of the rain cap. I called tech support and was told that the elbow should not be used in either case. As my venting is vertical I was concerned about rain getting down into the heater through the open hole on the rain cap that is for the exhaust venting of the heater.
I had this unit professionally installed two months ago. It took a plumber 8 solid hours to do the job. It is working like a charm --- endless hot water and energy efficient. It is slightly noisy when water is being heated. A sophisticated piece of equipment like this should have an inline descaler to keep it operating at peak efficiency, which is an extra cost. Rheem tech support is very knowledgeable, but the wait time to to get a tech on the phone can take 20 minutes.
Answer: yes