Gas Tankless water heater options

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maxdad118

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im torn between brands of tankless water heaters, anyone have a favorite or brand to stay away from? Im thinking Noritz or Rinnai and it seems all the companies have bad customer support.
 

Puddlesx5

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I personally chose Noritz. I fix all types of tankless heater and can tell you all the support is very professional. I think the problem is the tankless manufacturer's want a certain amount of knowledge to work on the heaters (and rightly so).
The Noritz has a thicker material heat exchanger ,but both work well.
 

maxdad118

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So if I have a 3/4” cold feed can I reduce the hot down to 1/2” after a few feet? Most of the hot water pipes were previously changed to copper by somebody before me. Will the tankless still work as it should?
 

Puddlesx5

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You can but why?
To keep a tankless heater firing you will need a minimum of 1/2 gal per minute flow. If it drops below that the heater will stop firing. In winter my tankless is set to 120°,summer is 115° which for me is plenty warm.
Try to keep the proper size water pipes or when the house is sold it will have to be fixed at your expense.
 

Snoonyb

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There should be a manifold of sorts distributing too the two bathrooms and that would be the point of reduction.
 

maxdad118

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I’m just saying what it is, it’s been working fine with our 40 gal, I’m just wondering if it will throw an error code.
 

Puddlesx5

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It will work fine. Just don't turn the temperature up too high 120° is the highest I would set it. If you don't have enough gpm it will just shut off. Not something you want to have happen mid shower.
 

maxdad118

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Yeah I keep my tank at 120 in winter and 110ish in summer. Thanks!
 

maxdad118

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So I’m deciding to get the Noritz NRC 711 OD, I have a 3/4” copper cold feed that needs to be plumbed to it, then I will need to get into my crawl space and install a 1/2x1/2x3/4” tee pretty much between the 2 bathrooms and plumb out for hot side. Still need an AC outlet and plumb the gas to it (have a 1” feed dedicated for it).



.
 

Diehard

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So if I have a 3/4” cold feed can I reduce the hot down to 1/2” after a few feet? Most of the hot water pipes were previously changed to copper by somebody before me. Will the tankless still work as it should?
I believe the primary reason for the 3/4" connections is to minimize pressure loss at maximum flows.
The consideration of 1/2" vs. 3/4" down stream should be based on...
Pressure loss.
Anticipated flow rate.
Noise.
You want to insure that all your flow demands will be met without excessive pressure loss.
If your water service pressure is relatively high then you would not be as concerned with pressure loss but may be exceeding the recommended velocity in the smaller size piping, which in turn gets noisy.
If you already have 1/2" piping downstream of your water heater and were happy with water pressure and flow throughout the house and have not or do not plan to increase your demands, than it's possible that you could get by with your existing 1/2" piping. It may boil down to how much pressure loss your proposed tankless unit will impose on the system.

Edit: Those tankless water heaters I believe were known to have a substantial pressure loss and that why their connections are 3/4". I suppose it's possible that your new tankless unit could cause higher pressure than what you had before and could impact pressures down stream. Without the calculating all out before hand I suppose I suppose you could result in lower pressures at your point of use. Do you have the option to wait and see if larger pipe would be required to offset the added pressure loss of the tankless unit? I think some of the newer units have improved on pressure loss.
 
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Diehard

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Just looking for the pressure loss values of that unit and all the spec sheets I find don't include it. Out of curiosity, I may give the factory a call.

Looking back at dates of comments, etc. I see you plan to run 3/4" to a split for the 2 bathrooms. That sounds like a good idea.
 
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maxdad118

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Thanks, I get what you are saying. I could keep the 40 gal connected to see if the 1/2”works ok before disconnecting it all the way. Actually, I am in no hurry to remove it and thought about keeping it in the loop as a backup. I’m mainly getting the tankless for the endless hot water feature.
 

WyrTwister

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Will your kitchen hot water be sourced from the tank-less water heater you are proposing .

Wyr
God bless
 

Diehard

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Well I found some info on that unit. I see it's an outdoors unit.
Don't know your location or lowest incoming water temp in winter time, but here's what to expect for gpm at a particular temp. rise.(Example: If your coldest incoming water temperature was 50 degrees F, and the tankless was set for 120 degrees, you should get 4.2 gpm of 120 degree water.)

Noritz NRC711 OD.jpg
(That pressure loss would be "about" equivalent to 100 feet of 1/2".)
 
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WyrTwister

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You might consider taking your 3/4" line , from the water heater , to a fitting with 1 - 3/4" & 3 - 1/2". To feed the 2 bathrooms and kitchen .

Or 1 - 3/4" & 4 - 1/2" . To give you an extra , should you ever need to run another hot water line to a different location , in the house .

Wyr
God bless
 

maxdad118

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I planned on 3/4” from the tankless to the crawl space with a tee at the 1/2” so basically the same thing, no? I imagine I could separate all the 1/2” lines and run 3/4 closer to the fixtures but think it should work without doing so. I guess I’ll find out.
 

maxdad118

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Well, between working, umpiring and watching my sons h.s. games, I decided to hire out an electrical and plumbing contractor to install an outlet and plumb the hot and cold to the tankless. I bought some unistrut and spring nuts to mount it. Gas has been plumbed for a few years now. Looking forward to getting the endless hot water feature!
 

maxdad118

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I still need to get an ‘in use’ cover for the outlet.
 
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