Combine Tankless Water Heater with Tank Water Heater?

15 years ago

We have two 50 gal. electric tank hot water heaters plumbed in series in our basement (i.e. the output of the first heater flows into the second heater and then to the house). the first heater has corroded and needs to be replaced.

Is it possible/advisable to replace the first tank heater with a tankless heater? I figure the second 50 gal tank can serve to normalize the flow of hot water into the house.

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mungo

15 years ago

Some people do as you suggest but with only a 5 gallon electric tank after the tankless. You could look up those discussions and they could give you a more thorough discussion. Like he said the search term would be "buffer".

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Comments (9)

zl700
15 years ago
What you are referring to is a buffer tank after a tankless, and defeats the purpose of a tankless unless there is a circulator to maintain temp in the tank, otherwise is will go cold unless heated with electric elements, which again defeats the purpose.

With regards to twin tanks, although the initial draw of tanks piped in series is higher, the 10% reduction would be better given up to pipe two tanks in parallel, so that both had equal usage and flow rates would be higher.
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Guys if you read the post, the reason the tank water heater was so expensive was due to the construction required to get his house up to code. I personally like my tank heater. If your changing from a tank to tankless there is alot of work to do. Moving water lines, moving gas lines (possibly upgrading gas line size too) and running a new intake/exhaust if using gas, upgrading the main service amps if using electric. Some things to consider Tank Heater Pros Costs less to replace in the future Easier to maintain (Tank water heaters are easy to flush out every year) Easier to install (dont have to upgrade gas line or main service amps) Gas water heater will still operate in power outage (electric will still have some hot water to use for a while till power kicks back on). Cons Not as efficient as tankless No Tax Credits Hot water limited by FHR (first hour rating) Tankless Heater Pros Unlimited hot water More efficient Saves space Cons Will cost more in the future to replace (there is no guarantee the tankless will last longer than a tank version, the heat exchanger can go bad and that is the most expensive part of the tankless) , Harder to maintain (you need to try to clean those tankless heaters out every year with a descaler so they stay working efficiently) Harder to install (upgrade gas line or main service amps) Tankless heaters have a limited throughoutput. While it is unlimited hot water, it can only supply so many gallons of hot water at a time Will not operate in a power outage. A tankless water heater is controlled by electronics whether the heater is gas or electric does not matter. Requires minimum gallons per minute from city water supply, some people have not been able to install due to that problem. Consumer reports note that users complain of inconsistant water temperatures. http://www.consumerreports.org/cro/appliances/heating-cooling-and-air/water-heaters/tankless-water-heaters/overview/tankless-water-heaters-ov.htm Another good site to look at: http://www.waterheaterrescue.com/pages/WHRpages/English/Longevity/tankless-water-heaters.html
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Thanks much everyone ! Another reason that got me thinking along these lines is to do space heating using the hot water. What I was thinking of was to use a heat exchanger on the pipe coming back to the tank and use that to heat the home (though forced air). I have to admit I haven't done any calculations on the effectiveness of this, but it is just a thought. Space heating does cost a good bit (we run the heater about 7 months of the year). It is clear/sunny most of winter. Besides, my dad prefers to keep the house at a toasty 78 resulting in high energy bills. What I imagined is that I would get most of my space heating bill (about $1000/year) reduced this way.
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Hi Charles Ross Homes, Thank you for your thoughtful response. My home is a 1960 single story ranch situated in a Southeast Texas. All of the homes I have owned here have had the water heater (tank or tankless) in the attic. City code permits for this install location. Not all, but many, homes in the area have water heaters in the attic. I understand about the potential leak issues - we have water leak monitoring and emergency shutoff and water collection pan/drainage in place. My garage is detached and on the Northeast side of my property. It would take quite a bit of work and cost to move the water heater (and associated gas/power) to the garage. I could consider putting the Navien on an outside wall, but that would require it to be installed on my master bedroom wall or in an unprotected area. I don't feel it would help with the sound issue anyway and there is the cost issue as well. I think the Navien NPE-240A is just not a good fit for my needs and constraints -- given its operations and operating requirements. My last instant water heater was a Noritz - put in by the previous homeowners. I never heard it operating. I'm sure it made some sound but that sound wasn't loud enough to permeate to any of the living areas. They don't make that Noritz any longer. Do you have recommendations or suggestions for a "quiet(er)" tankless system? Thanks.
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Wow....sounds like my house. We live in a rural area and have well water and propane. Our propane water heater died last month it was impossible to replace it because it was a side vent water heater and we couldn’t find one anywhere. We ended up going to Home Depot and getting a tankless propane water heater. I think the cost of it was around $1500. Our home is about 2500 square feet, two stories. My husband was able to install it in 2 days. Of course it’s in the basement and had to have a side vent. They make two models one for inside installation and one for outside. We have of course the inside. According to the information on this water heater four people could take 4 showers at the same time and not run out of hot water. Since there’s just the two of us that’s not going to happen. I do however run the dishwasher and washing machine at the same time. So far so good. One thing I noticed is that it takes longer for the hot water to get where it’s called for than the old conventional propane water heater. It’s off until the hot water is called for, than it fires up and you run the water in the hot water tap waiting to flush out the cold water waiting for hot. It’s nice that it’s not on when not needed but if I could have found a water heater to replace the old one I would have stayed with the conventional. Time will tell as to whether or not we are saving on propane. The water heater we purchased was a Rheem. There is also a water filter screen on this tankless unit that should be taken out and cleaned each month. Since we are on a well this might be required more often. Our old conventional heater was set at 130 degrees. It was happy, we were happy. This tankless one needed to be set at 140 degrees. We were just not getting the hot water we needed at 130 degrees. Now it colder here than where you are we live in western Washington state, and the basement is not heated. Maybe the pipes down there are colder even though they are wrapped. Sorry this is so long I wish you the best of luck.
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jake2007
15 years ago
Are you looking at a gas or electric tankless?
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jchang
Original Author
15 years ago
I was looking at an electric tankless. I already have an electric tank heater that is working properly. After doing some research it seems like the most sensible thing to do is just to replace the broken tank heater with another tank heater.

Thanks for the advice.
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jake2007
15 years ago
Yep, I would rarely recommend electric whole house tankless. And there would be no reason to do it in your situation.

There could be a good argument for one gas tankless to replace both of the 50 gal electric though, if you have gas available.
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Michael Thomas
4 years ago
The water heater pros in my area is Clarke & Rush. They know everything about water heaters. I was dealing with a leaky water heater and looking at maybe getting a tankless system. Talked to the reps there and they gave me all kinds of information. Ended up with a new 50gal that works great and was super affordable. Tankless seems legit, but not really for me, I guess.
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nwsvndr
4 years ago
The disadvantage of tankless is that you may not have enough hot water to supply multiple simultaneous uses (running 3 showers at a time, for example). So what I'm thinking is a tankless and a tank heater feeding into a mixing valve such as a Watts LFMMV. Set the tankless to deliver 110F and the tank to deliver 120F and set the mixing valve to supply 110F. Then under normal conditions the the mixing valve calls for "cold water" of 110F from the tankless but if the tankless can't keep up and falls below 110F then the mixing valve mixes in hot water from the tank to maintain the 110F. Would this work?
Jake The Wonderdog
4 years ago
Yo, this is an 11 year old thread... move on already!
arson114
4 years ago
nwsvndr, I'd love to know what you ended up with and how it turned out.

Combine Tankless Water Heater with Tank Water Heater?

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Combine Tankless Water Heater with Tank Water Heater?

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