Tankless Water Heater Q? (1 Viewer)

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I am thinking of putting in a tankless water heater. Our water heater is old and not always consistent. I see the Home Depot has a 27kW and 5.3GPM heater at a great price with good reviews. My wife takes a bath and I take a shower typically once a day*, but we have a little boy on the way (not really going to be a problem, if any, for quite a few years). We don't bathe at the same time. I wash dishes (by hand) once a day for lunch.

*sometimes twice.

Typically, is 5.3GPM sufficient for my needs?
 
I looked into it a few months back when my tank sprung a leak. I could easily afford the new tankless heater itself, however, I quickly learned how much of a pain in the butt it is to retrofit from a tank heater to a tankless. The extra costs add up very quickly and could turn into a huge project. For me, and for most people, it's not worth it. If you are creating a new utility room, or if your current utility room is in the garage and unfinished, it might be worth it to you.

#1) You will probably need to replace the entire vent system for a tankless heater. The tankless heater heats up so much faster it creates a lot more steam. You will need to replace your current venting with all stainless with a drain system.

#2) A tankless heater needs a larger gas line than a tank heater because it requires more BTUs. Odds are you will have to replace your current gas line with a larger one or run a new larger gas line. This could mean sheetrock work depending on your current line is run. Plus you will need to pay for gas pipe and that could be a large costs depending on how far away your main feed is.

#3) If you are going electric and not gas (I had an extra electric outlet as I switched to a gas dryer) you need a different type of circuit than a dryer or tank heater. I would have had to run a whole new electric line back to the panel. I don't remember the exact details because by that point I was disgusted and just decided on a new tank heater


Hope this helps. If you do put one in, please let me know about your experience. Someday I still hope to have one instead of a tank heater.
 
I had a Rinnai gas tankless water heater installed in my new construction home 10 years ago. Haven't had a bit of trouble from it (so far). Anyway, they said my heater was good for 8 GPM and that I could run 3 appliances at the same time (2 showers and a washer etc.) at the same time. So far, they're right. I've never run out of hot water in my shower no matter how many fixtures it was supplying.

So to answer your question, I think you could run 2 sources with your 5.3 GPM heater at the same time and not run out.

The issues that boutrous brought up are a completely different matter. Good luck.
 
I had a similar experience as Boutros--after we had a bit of trouble with our current water heater and the plumber mentioned that it's starting to show its age, I talked to the tankless specialist he recommended. And that guy talked me out of it, citing the same reasons Boutros mentions. He said that the tankless is worth doing in a new house or in a major redo, but didn't recommend it for an older house.
 
That's enough water for a 3/2 with 3 people probably, but the cost of the retrofit is probably not going to be worth it.

Depending on your electrical system you might not have enough capacity to run it without major work. If it's gas, you'll probably need to add ventilation and/or change out the gas line.
 
Thanks for the info... I thought it would have been a somewhat easy switch. Now that I read more, it looks like the task could cost more than double once you start buying everything else. I thought these units could be mounting to the outside wall of the house? Is that only certain models? I have a separate breaker box outside for a second AC with available spots for the 3 breakers. I was thinking of mounting it near that so it wouldn't take much wire. Am I thinking wrong?

I was wanting to get away from the gas and go total electric. My gas bill runs about $25 a month and it's just the hot water heater on "normal" setting. Seems like it isn't very efficient.
 
Thanks for the info... I thought it would have been a somewhat easy switch. Now that I read more, it looks like the task could cost more than double once you start buying everything else. I thought these units could be mounting to the outside wall of the house? Is that only certain models? I have a separate breaker box outside for a second AC with available spots for the 3 breakers. I was thinking of mounting it near that so it wouldn't take much wire. Am I thinking wrong?

I was wanting to get away from the gas and go total electric. My gas bill runs about $25 a month and it's just the hot water heater on "normal" setting. Seems like it isn't very efficient.

If your gas bill for water is only $25 you're never going to save enough money to make it worth the cost of changing to tankless.
 
Thanks for the info... I thought it would have been a somewhat easy switch. Now that I read more, it looks like the task could cost more than double once you start buying everything else.

Yep...I can give you a real world example. We retrofitted our previous house to install a tankless. Mainly, our problem was that if we filled our whirlpool tub, that would empty the tank of the water heater that was there, so we wanted the ability for more hot water.

Fast forward two years, we built a brand new home, and installed the same model tankless water heater in our new home.

The difference between the cost to install in the old house and the new house? It cost us almost $800 more to install the tankless in our old house. This was due to needing to run a brand new gas line because the one that was there wasn't large enough for a tankless, and having to do roof work to accomodate the increased side of the vent piping.

I thought these units could be mounting to the outside wall of the house? Is that only certain models?

I'm pretty sure it is. We have a Rinnai, and while I'm not sure of the model number, I do know that the last character of the model number is "i," which signifies it is for indoor use only.

I have a separate breaker box outside for a second AC with available spots for the 3 breakers. I was thinking of mounting it near that so it wouldn't take much wire. Am I thinking wrong?

No, you aren't thinking wrong. Mounting it near the breaker box will take less wire. But, that doesn't mean it's the best choice. The farther away it is from the outlets (tubs, sinks, etc), the lower the temperature will likely be when it comes out. That can affect the efficiency.

Ideally, you'd want it to be mounted an equal distance from every outlet. That way, everyone gets the same temperature hot water.

I was wanting to get away from the gas and go total electric. My gas bill runs about $25 a month and it's just the hot water heater on "normal" setting. Seems like it isn't very efficient.

As DTC said, if your gas bill is only $25 a month, you likely won't see much savings on a month to month basis...and, unless you can do the work yourself, most of it will be eaten up by paying someone to install it for you.
 
You will probably need at least two 60 amp circuits to power a 27Kw heater. That could add considerable cost to the project depending on how far from your main panel the water heater is located and accessibility. My opinion would be to get a good high efficiency water heater tank and a programmable timer.

Something else to consider is if you have or plan to have a whole house generator. Most conventional water heaters only draw 5Kw. A good sized generator would be able to handle that load ensuring you also have hot water when the electricity is out. You would need a hefty generator just to run a 27Kw tankless heater.
 
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