What I Wish I Knew Before DIY Installing A Rheem Tankless Gas Water Heater 

This is one DIY project that can’t replace skilled trades and knowledge. There are gas piping sizing and gas meter sizing calculations to consider. Most residential gas meters are 250 CFH. A 200,000 BTU tankless would consume 200 CFH, leaving only 50 CFH for remaining gas appliances in the home. A gas furnace would put this over the top. Therefore, gas meter and regulator would need upsizing.

This was an exact replacement for the old one that lasted about 10 years.

just installed one of these today. the author of the video is not kidding about the vent pipes. they won't have them in the store and forget about elbows. we ended up getting a 5" sheet metal tube and a 3" sheet metal tube and rigging the double pipe setup ourselves. the 3" tube is your vent and the 5" is your air intake. It wasn't that hard, but it took a good bit of rigging to get it done. Fortunately for us, this was a first time gas appliance install, so when we ran the gas lines we just went with 3/4" all the way from the meter to the utility room.

When we built our house we sized the gas for two tankless units. 1.25" gas trunk through the house at roughly 7" WC. We never even installed the second tankless for the far side of the house. No need. These things are great and a single is enough for 3 baths and an always bustling kitchen. Even hooked up an outside spigot to kick out hot water to the rear patio (kiddie pool fun in the winter) 👍

You are going to develop corrosion on the copper pipe where those steel straps contact the copper due to electrolysis. Better to use plastic or copper straps.

I bought a Noritz tankless and had it installed almost a decade ago. Love it. So glad I got rid of my tank. My plumber told me all the parts I needed, and I got them from a local plumbing supply store rather than Home Depot. Some things you just gotta go elsewhere to get all the components.

Pulled out my Rheem and installed a Navien about 10 years ago. The Rheem failed about once a year and error code required a burner assembly cleaning. Wasn't dirty. It was a known problem. Got a replacement control board and still had issues. My house has a salt/water softener system and I've not cleaned the Navien with vinegar yet but plan on it soon. The NPE-240A has an internal pump just in case you have a facet that takes a while before you get hot water. I haven't touched it in 10 years but started researching cleaning and adding the pump feature to get hot water to the kitchen quicker. I bought another Navien for a retirement house, I liked it so good. It uses 2 inch PVC pipe for the vents. Cheap and easy. I've got a 1 1/2" gas feed line into my home so we were OK on the gas feed. The Navien had a 3/4" gas line supply line with a 5/8 for the last connection.

Ok if you read the manufacturer's installation instructions it says you can install a tankless on a ½" piping as long as the ½" piping doesnt exceed 25' and the ½" must connect to a ¾"(+) pipe.

I went with a one inch pipe system all the way from the meter to the water heater, but I installed it outside and it works great

I recently installed Rheem condensing 199k unit. Did my research. Had gas company upgrade my meter. Ran 1" decreasing to 3/4" black pipe all the way to unit. Ran 2" pvc intake and exhaust. Installed lime scale filter on cold water inlet pipe along with service valves. Will change yearly. I have pump and hoses to descale with vinegar yearly. Ran 1/2" increasing to 3/4" pvc condensation line through wall to outside. Also will clean out cold inlet filter biyearly. I'm not gonna say these units are easy to install but with some prep and knowledge I believe a handy homeowner CAN install and maintain one of these units and save alot of $$. LOVE MY RHEEM. Can't wait to see electrical savings over 50 g electric tank that it replaced.

I doubt that any of these parts you had a hard time finding in 2020 are any easier to find now at the end of 2021. Thanks for your time, this was helpful. My customer is aware that it may take a little time for parts to come in

They have flat sheet at the big box to make your own double exhaust. I saw them yesterday actually. Ymmv. When I installed my gas tank water heater 10 years ago the exhaust was the biggest headache as well.

That's why condensing models are easier to install. I went with a 199k model. But my gas line was already 1.5" when I had the house built. I've got 2 furnaces and all my appliances are gas.

thank you for posting

Hello, not a bad install. Definitely better than most plumbers with at least two years experience. I do want to add, be prepared when something does go out on this unit. You will need to call customer support and they’ll walk you through diagnostic’s. Then the part will need to be mailed. Hopefully two days later if you pay for the overnight. I’ve never found a place that carries parts for these tankless w/h. The other problem is when the power goes out, so does your “hot” water. Where a tank would be just fine. Change those straps as well.

Would like to see how the stainless venting is installed. Good job!

You did a great job. DYI is always frustrating but you learned and did it,

FYI I walked to a new development a mile from my 20 year old house. All new houses in Calif require tankless. They have 1.5 inch gas line going to garage, branch of 3/4 at tankless heater, reduced to 1.25 going to furnace, branch of 1 inch at furnace, reduced main line to 1 inch, branch of half inch to gas dryer, main reduce to 3/4 to stove, branch of 1/2 to backyard BBQ.

no disrespect but the gas shutoff should be below the union. nice video and pipe job.

Fine job on the install, next time you will be much better at it from what you learned. I know it can be frustrating being a hopeless do it yourselfer like me. I live in a very rural area and getting a "professional" to install and service anything is hit and miss at best. May take tons of research to get a job done right but you will never regret learning something. Yes I installed a Rinnai (condensing) tankless 2 years ago and it has been flawless. Way cheaper to run on propane than the electric heater I had for 25 years. One of my professional horror stories goes like this. Had a "professional" install a steam boiler in a commercial building. The unit flooded at random since day one and not infrequent water damage up to the second floor of the building. Steam radiators dump water out the steam vents when flooded with water. 3 "professionals" from different companies including the installer hired to fix it and failed. Probably 5 total fix attempts. I sold the building to a friend and I told him I would have it fixed. Yes I had to fix it myself, float valve defective and hitting the top of the housing. Yes the vaIve was installed correct/level. I just put a dent in the float where it struck the housing and guess what no more flooding and my friend said the boiler ran perfect for years and never flooded once. I told him I had to fix it myself so he was aware that it was a looser DIYer that had to fix it. Funny how the construction codes require a licensed professional but never mandate a professional outcome. I am a professional (medical) and never complain about DIYers. Just help people when they need help whether they are the cause of their misfortune or not and skip the "I'm a professional and better than everyone else" attitude.