Tankless Water Heaters

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Topic: Tankless Water Heaters

Home and Garden December 15, 2011 at 10:04 am

Tankless Water Heaters

Anyone have a gas tankless water heater and can speak to its effectiveness sufficiently heating the icy cold water in the winter? We’re seriously considering one, but from what we’ve read, getting the water hot enough in the dead of winter can be a bit of a problem.

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From a reader who’s not registered:
““I don’t have a tankless water heater but considered getting one after a bathroom renovation and did a lot of research on them. One of the things that will affect the heater’s ability to heat cold water is the amount of BTUs that the unit operates on. The greater the temperature differential (the difference between the tempearature of the ground water and the hot water temperature you are looking for) and the water flow (the gpm of hot water you desire – the more people, fancy bath fixtures, etc., the more gpms you want) the more BTUs are needed to heat the water. When I had a plumber affiliated with a tankless heater company come to look at my place to see what I could install (this was a free visit) I was told that based upon the BTUs being supplied by my gas line I could only get a relatively low capacity (low gpm) unit because of the limited amount of BTUs left after accounting for other gas-powered appliances in my house – which in my case was only the hot water heater and the furnace. I believe you can have your gas line upgraded to supply more BTUs but you have to pay for it and it’s not cheap. A high BTU unit would have operated perfectly fine on my low capacity line until Winter whn my furnace kicked in regularly. At that point the BTUs available to heat the water would drop significantly, causing the unit to be ineffective. This BTU issue may be the cause of the complaints you’ve heard about poor tankless water heater performance in winter. I believe that if you check on Washington Gas’ website, there is some way to determine the total number of BTUs being supplied to your house. Come to think of it, the information may even be on your gas meter. You can look up the average temperature of ground water for this region to get a sense of how much it will have to be heated. Download and study the installation manuals and spec sheets for any unit you consider. All the info you need to make a smart choice will be there. Good luck.”

We bought our house last December which has two gas tankless w/h’s.  The only issue we’ve ever encountered is we have a 4 level row house, tanks in the basement and master bath on the top level.  We have to run the water for several minutes before it gets hot, but after that you’re good to go. Main level was takes around 30 – 60 seconds to heat up.  I love the fact that I can take long baths and never run out of hot water. My old townhouse ran out of water 1/2 before the tub was filled up.  

I have a Rinnai tankless water heater in my 1br apartment and it is wonderful. I turn my shower on and the water is hot pretty much instantly. It seems to take a little longer for the water to get hot in the kitchen and bathroom sinks (and by a little while I mean maybe 20 seconds). I can’t speak to how it would work in an entire townhouse, but it works great in a smaller apartment.

I got a 199,000 BTU tankless water heater, in addition to my furnace, and gas stove. I spent some time nerding over the numbers myself, and realized that I needed a bigger meter. I called Washington Gas, and once I got through to the right person, it was pretty easy. He did a similar calculation, and scheduled me to have a bigger meter put in – overall relatively painless, and it didn’t cost me anything.
That, and I love my hot water.


I just recently started looking into this and am considering replacing my boiler and water heater (both gas powered, and both needing replacement in the next year or two) with a tankless boiler/heater combination unit.  As I understand it, these can provide hot water both for radiators and for hot water for your house.  I don’t know about the BTU limit issues, but maybe this would solve the issue with the water  heater and furnace trying to consume gas at the same time?

I have one in my regular house any my weekend house.  They are good if you get the right size, more expensive to install by about 1000.  Also, don’t buy off the shelf at Home Depot.  Get a Rinnai.  (Total cost for ours, with install, was 3200). 

I am wondering what is the advantage of a tankless WH. My understanding is that the new WH (tank) have much better insulation and are much more efficient. I did a little research a while ago, thinking that the advantage could be about saving space, but then I found that with the tankless WH you still need to have some clearances that basically makes you not save anything. On top of that, as somebody mentioned, the cost of the device and installation are more expensive. So I am curious about why people prefer tankless?

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