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on June 6, 2011
After installing a new high efficiency gas furnace and central air conditioner, I discovered that my 15 year old gas tank water heater was leaking. I had a choice: either replace the tank heater with new one for about $500.00 or upgrade to a new high efficiency gas tankless water heater.

I wanted to go with the tankless choice to provide endless hot water, but I was concerned with the potential difficulty of the installation. There were three key issues with replacing a tank heater with a tankless water heater.

First, I wanted to keep the new water heater in the same central basement location as the old tank water heater. That necessitated the choice of a "Condensing" type tankless water heater because they vent the exhaust through standard 3 inch PVC drain pipe (about $1 per foot). The non-condensing type tankless water heaters have a higher exhaust temperature and require very expensive stainless steel exhaust piping. This type of heater are usually mounted on an outside wall to shorten the exhaust pipe length. So, I chose the Rheem condensing tankless water heater, but I still needed to run two 25 foot runs of PVC pipe to feed the intake combustion air and to exhaust the combustion gases. Since I had just done the same procedure when I installed the 95% efficient gas furnace, I knew that it was time consuming, but within my abilities.

The next issue was the water pipe plumbing. I have done a little copper pipe plumbing in the past, it was functional but not pretty. So, I knew I could get the job done. The key problem was that the old tank water heater had the cold inlet and the hot outlet pipes at the top of the tank and the tankless heater needed the connections at the bottom. I would guess that they use the bottom connection to eliminate the chance of water leaking on top of the heater. The heater has a very sophisticated computer control system that needs to be protected. I mounted the new heater on a 2x4 frame with a OSB sheathing and ran the water pipes behind the mounting between the exposed stud wall of the mechanical room. This also helped free up room to run the PVC piping up and through the exposed floor trusses in the ceiling.

The last issue was the natural gas supply. This tankless water heater requires a much higher gas flow supply as compared to the tank water heater it replaced. While this might seem counter intuitive; why should a more efficient appliance take more fuel than a less efficient appliance? The reason is that the tankless water heater must heat the cold water very quickly, in just the few seconds that the water is running through the heater on its way the the hot water tap in your house. This water heater needs 199,900 BTU of natural gas. My old tank water heater used 40,000 BTU. This large increase required two changes in the gas supply. First, I had the replace the 1/2 inch black pipe gas line that fed the old tank water heater with a 3/4 inch supply line. Second, I need to have the gas utility company replace the 240,000 BTU meter outside my house with a upgraded 400,000 BTU meter to accommodate the nearly 200,000 BTU tankless water heater, the 115,000 furnace, the 66,000 gas range and the 20,000 gas clothes dryer. Some utilities will do this for free, but in my area (near Chicago) they charge $220.00 minus what they "calculate" as increased revenue from additional gas usage. While there will probably be less overall gas usage, the utility just looks at the difference in the old gas appliance and the new gas appliance. They estimate the new meter will cost about $160.00 net. I don't need to get this completed until the winter heating season when the furnace needs to be run at the same time as the water heater.

I didn't have much problem installing the Rheem tankless water heater. But it did take two solid days of work. I was able to perform the whole install without any assistance. I am a pretty good DIYer, but I don't think that it took any great skill, just a thorough reading of the instructions (the Rheem instructions are very good and they are available on their web site), a little YouTube How-To video research and a written plan including how to mount the heater and making the connections. I watched the set of videos on the Rheem web site. While they cover the older non-condensing type heaters, they are a good starting point.


I don't know what it would cost to have a professional install this heater, I would guess that it would take 6 to 8 hours of labor plus supplies. I spent about $350.00 on copper piping and fittings, gas pipe and fittings, PVC pipe and fittings and various miscellaneous supplies. Also, don't forget to budget in a set of "Service Valves". They cost about $80.00 to $150.00 per set. They are needed to provide an easy way to periodically flush the heater to clean any hard water deposits.

The Rheem tankless water heater worked great right from the initial start-up. My family enjoys the endless supply of hot water and we don't have to plan our showers around each others schedule or the the use of the clothes washer.
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on August 12, 2016
Works great. Be aware not really compatible with new clothes washer. I usually wash clothes that need hot while taking shower. That way water is preheated. Same goes for dishwasher. Also you need two roof ducts. May be issue if you live in a condo as I do ,I'm writing this 8/11/16. Also use roof ducts that are turned down and don't need rain cap. This unit needs to breath. It was a problem at first but my a/c guy figured it out quick
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on May 29, 2015
Make sure you separate the intake and exhaust vent.
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on February 12, 2013
I purchased this unit becuase my tank system just never seemed to have enough water. Currently we had a 50 gallon AO SMith which was only 3 years old. So when we got this delivered there was no rush to install it.

Well my 3 year old Smith died completly and my plumber came over and installed this unit. I must say instantly (after he was done) we had hot water and it did not run out. The unit is very nice and I am very happy with it.

For those of you considering this purchase get the instalation kit that is suggested. Otherwise you will find yourself searching for a 24hr plumbing supply. You must have a150psi pressure release and no Home Depot does not carry it.

Happy Showering!!!
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on June 20, 2013
Ok people I have a 13 and a 14 year old at home. A wife that always doing the dishes and laundry, and me who just wants some hot water to take a shower. Before this it was a waiting game of who could take a shower and for how long as the 75 gallon water heater was running constantly to catch up. Now My kid is in one shower, my wife is doing dishes and laundry and good ol dad is enjoying a nice long hot shower. We also have seen 1/3 taking off our monthly gas usage. We had it installed about a year ago and it will have paid for itself in 2 more years. I couldn't be happier.
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on December 10, 2012
Our 8 year old traditional tank water heater rusted out. It was my fault- I was good about draining the tank every year, but was thinking it was a 10-year warranty heater, not the 6-year it actually was. The manufactureres design the anode to protect the tank long enough for it to make it to the warranty period, plus a bit. Mine did, but not by much.

Anyway, I replaced it with this Rheem tankless unit and have been very happy with the performance. We have a family of 4 and have not had any problems with hot water except the one time the kids tried to shower while my wife was filling the bath tub. In that instance, the system was unable to provide sufficient pressure for 3 users at once. BUT there was no worry about running out of hot water once the tub was full!!! That is a huge advantage to the tankless system, and it was the only time in a month of use that we have had any issue with the tankless setup.

One operating note: you may hear the system running as it starts every time there is a need for hot water. It is not obnoxious, and is barely noticeable with the heater in the basement and the bathroom about 20 feet away and one floor up. The door to the room with the heater is left open, perhaps the noise would be reduced more if it were closed but I think a fair amount of it is coming through the framing of the house, etc. I may play with putting some sound-deadening material on/around it at some point, especially the air vents, but that is only because I enjoy tinkering.

Installing it myself, including moving gas lines and copper water lines took some time but was not techincally difficult. Do give thought to venting. I was fortunate enough to have an extra make-up air supply that was unused and did not have to mess with adding an exterior penetration.

6 Month F/U: We are still happy with the water heater but have a couple of points worth mentioning:
1) There is an annoying cold water "slug" when initially using the hot water, especially if you are using it intermittently. Example: Run the water (takes a little bit longer to get hot than with a conventional heater, with about 25' of pipe) until it is hot. Use hot water for 30 seconds, turn off. Turn back on th ehot water and you get a brief supply of hot water followed by 20-30 seconds of cold water before the hot comes through again. I <think> what happens is the valve in the heater allows cold water to pass through the heater, maybe to cool the system?, each time you turn the water off. When a hot water request is sent again the cold water in the system is joined by more cold water let in when the valves open again, before the water has been heated. This problem has been documented elsewhere on the web and I think the solution for us will be to add a small (2.5 gallon) tank heater downstream from the on-demand heater.
2) When filling a bathtub there is insufficient hot water at an other tap. The supply to the tub seems to equal the output of the on-demand unit and anything extra results in cool water.
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on June 17, 2012
The Rheem RTGH-95DVN Prestige Indoor Direct Vent Condensing Tankless Water Heater, Natural Gas is a great product so far, after 2 months of use.
The product shipped promptly and was on my doorstep in 2 days. It is very lightweight and seems well built. Conversion from tank to tankless in a larger attic space was not quick -- it took quite a number of hours (more than 8) for a plumber and helper to complete, including removing the old unit, cutting a new exhaust hole in the roof, adding an electrical outlet to power the unit, plus a couple runs to the nearby supply store for misc items. Note: The condensing part of this heater means there is a small amount of water (condensate) that drains out of the bottom of the unit during normal use. Make sure to connect a drain tube and run it to a drain that can accept the continuous, albeit small, flow of condensate.
We love the tankless system. The hot water arrive at our faucets as quickly as the tank system, but it never runs out! It is quiet (can't hear anything when it kicks on). The hot water flows even with the faucet barely turned on.
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on June 7, 2012
I'm really happy with this choice... It took me about 2 days to get this up and running.. the installation is not easy from finding the right place to securely hang it, gas pipping and sizing, ventilation and the water hook-ups.

Also, you really need to have the appropriate gas meter to handle the required BTU's. So add up all the btu's from all your existing appliances and add 200K on top of that....Then, call your gas company to determine if you have the appropriate gas meter to handle the load. Columbia Gas changed it out for free. Again, its not that easy but at the end of the day I am really happy. However, its summer time so the real test is how it will work in a New England winter. stay tuned!
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on October 7, 2012
I've installed 3 of these Rheem tankless water heaters and all worked perfectly. Factory support is excellent as well. I'll never go back to a hot water tank.
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on December 10, 2012
This is the best there is very happy with the way it heats the water extremely fast. I found it easy to install myself and I am not a plumber the toughest part is working the the venting thru the attic and the outer wall. If you are replacing a water heater or going new this it it. Best product for going green in todays world
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