Tankless Water Heater Question

"Galileo Humpkins (aka MC Clap Yo Handz)" (galileo-humpkins)
06/10/2019 at 19:38 • Filed to: None

Quick question for those ‘in the know’ either professionally or based on their own usage/experience with tankless water heaters. We are deciding on the upgrade to a tankless water heater. There are 3 options, all 11 GPM, natural gas, indoor, same warranties, similar pricing, similar features . A ll seem fairly comparable, so my question is, which brand would you recommend, Rheem, Noritz, or Rinnai? Rheem is the more familiar name and has much lower reviews and that worries me a bit . Noritz I’d never heard of until shopping around, the reviews are pretty strong . Rinnai has stellar reviews and I recognize the name but having never really shopped for water heaters I don’t know much about them.

Or, would you have a different recommendation? Thanks for the input.

DISCUSSION (80)

gettingoldercarguy > Galileo Humpkins (aka MC Clap Yo Handz)
06/10/2019 at 20:23

We just put in a hybrid Rheem to replace a failed electric tank heater. The savings are massive with this type. I have it set to straight heat pump during the summer which uses comparatively no electricity. It's not tankless, we looked at those but the efficiency of this is undeniable.

gmporschenut also a fan of hondas > Galileo Humpkins (aka MC Clap Yo Handz)
06/10/2019 at 20:35

Anyone have experience with an electric one? Sorry to hijack the thread

ranwhenparked > gettingoldercarguy
06/10/2019 at 20:39

My conventional electric water heater was installed in 1992, so I’m expecting it to go pretty much any day now. I’ve noticed Rheem sells heaters with plastic tanks that are supposed to last pretty much forever, for not a huge price premium, either. Did you get one of those, by any chance, or at least look at one ? I’m trying to keep some options ready in mind.

Galileo Humpkins (aka MC Clap Yo Handz) > gettingoldercarguy
06/10/2019 at 20:45

Interesting, I’ll look into that. Our only thing is we prefer to have very hot water, for long periods of time and our current 50 Gallon tank doesn’t cut it. It’s fine, but we think we can do better. After one of us showers, the other has considerably less time with adequately hot water (and my wife doesn’t take them nearly as hot as I do). It’s also 13 years old, so I expect it’ll need replacing soon anyway.

Deal Killer - Powered by Focus > Galileo Humpkins (aka MC Clap Yo Handz)
06/10/2019 at 20:45

I’d recommend neither of those options. Tankless water heaters require yearly maintenance whereas the typical tanks are set and forget. More parts equal higher costs to repair/replace. Unless space limitations demand it, I’m not a big fan of those H.E. Units.

RutRut > Galileo Humpkins (aka MC Clap Yo Handz)
06/10/2019 at 20:47

The plumbing for them is pretty pricey depending on your setup. I looked at a Rinnai before I replaced my last conventional, but the $10 per inch intake/exhaust concentric plumbing would have been incredibly expensive for me and difficult to service.

Galileo Humpkins (aka MC Clap Yo Handz) > Deal Killer - Powered by Focus
06/10/2019 at 20:49

Interesting, I was not aware of this. I thought the maintenance plans were pretty similar. Space is not a limitation, our current 50 Gallon tank is 13 years old and will probably crap out soon.

gettingoldercarguy > Galileo Humpkins (aka MC Clap Yo Handz)
06/10/2019 at 20:53

Same as us, we went to an 80 gallon from a 50. So , even when my hot water loving sister in law stays with us, nobody is caught out in the cold. Plus, we have the water temp set to 125 rather than 120.

Galileo Humpkins (aka MC Clap Yo Handz) > RutRut
06/10/2019 at 20:55

We obviously will have someone come have a look to see what the install would require and what the cost would be , and that will help us decide. $10 per inch sounds, extreme.

Galileo Humpkins (aka MC Clap Yo Handz) > gettingoldercarguy
06/10/2019 at 20:57

That’s good to know. I’m going to throw the hybrid into the mix. We’ll see once we have everything checked out to see what the cost differences will be and all the other specifics.

gettingoldercarguy > ranwhenparked
06/10/2019 at 21:00

I didn't look at too much, ours went out in the dead of winter and my wife was 8 months pregnant. I looked at the most efficient option and these knock it out of the park. Combined with a 500 dollar rebate from our energy company when the difference was 800 for straight electric vs hybrid made it a no brainier.

gettingoldercarguy > Galileo Humpkins (aka MC Clap Yo Handz)
06/10/2019 at 21:01

One thing I read for maintenance is to drain a bit every month to flush out sediment that collects in the bottom of the tank.

gettingoldercarguy > ranwhenparked
06/10/2019 at 21:05

Kinja'd!!!

Fuckkinja > Galileo Humpkins (aka MC Clap Yo Handz)
06/10/2019 at 21:08

I had a rheem when we had natural gas. It was great till we had a power surge. $1000 later it was back to perfect. I do the installs. Electric on demand takes 120 amps from the the panel. Nope.

Our 50 gallon 30 amp dual element heater just gets us by. P ropane is expensive

gettingoldercarguy > Galileo Humpkins (aka MC Clap Yo Handz)
06/10/2019 at 21:11

https://oppositelock.kinja.com/1835393391 is the link to my quote, check with your electric provider for rebates too. O urs has already paid for the difference in price and will pay for itself before needing replacement. Happy hunting!

BaconSandwich is tasty. > Galileo Humpkins (aka MC Clap Yo Handz)
06/10/2019 at 21:14

We currently have a Navian. I’ve lived in a place before that had a Rinnai, and I hated it. If you turned the water on part way, it would pulsate, and splatter everywhere. I dislike our Navian because it doesn’t seem to kick on when the faucet is only turned on part way.

Honestly, if I had to do it over again, I’d get one of the ones shown on the Fully Charged show that is a hot water tank, but uses a thermocline to only heat up so much water (heating it from the top down, instead). It seems like a better idea.

ranwhenparked > gettingoldercarguy
06/10/2019 at 21:17

Wow, those are some hefty price tags, I mean, nobody ever said owning a house was a good investment, but, still.

gettingoldercarguy > ranwhenparked
06/10/2019 at 21:21

Every year we've put 15-20 in maintenance since moving in. Think we're about good, so it's remodeling time I guess.

Texas Plumber > Galileo Humpkins (aka MC Clap Yo Handz)
06/10/2019 at 22:15

I would have to say Navien 240A. Stainless steel heat exchanger, built in circulating pump,and built in buffer tank. Also wifi capabilities for easy adjustments. Not to mention there is actually room inside the unit to work on if need be. You can even mount it indoor/outdoor all in the same unit. The unit is also field convertible from natural gas to propane depending on what you have. Superior product!

Plumbpros > Galileo Humpkins (aka MC Clap Yo Handz)
06/10/2019 at 22:19

As a Plumbing Contractor I always recommend the Navien Gas Tankless water heater. At 12 gpm, 199k btu's , 2" PVC Vent, you can’t go wrong. The NPE 240A comes with a built in recirculating pump.

Just_jr > gettingoldercarguy
06/10/2019 at 22:29

Steibel Eltron for electric or Takagi for gas. Very happy with both brands, best in there respective categories.

Just_jr > Galileo Humpkins (aka MC Clap Yo Handz)
06/10/2019 at 22:31

Steibel Eltron for electric or Takagi for gas. Very happy with both brands, best in there respective categories.

RedBaron134 > Galileo Humpkins (aka MC Clap Yo Handz)
06/10/2019 at 22:32

I’ve installed my own Rinnai and it cost less than 100 for the intake exaust setup. The run for me is about 15ft with 3 elbows. So not sure where RutRut priced his but they are much cheaper than that. I use mine for in floor heating and it also provides the potable hot water through a dual heat exchanger setup. Very efficiant and always have an endless supply of hot water.

lscrx > gettingoldercarguy
06/10/2019 at 22:44

My electric company replaced both of my electric water heaters (12 and 24 years old) at the same time with new ones for free. The only “catch” was that they have some capability of cutting power to them at peak load times... but they’ve been in for over a year and I’ve never had that be a problem.

The Snowman > Galileo Humpkins (aka MC Clap Yo Handz)
06/10/2019 at 23:16

The exhaust kit for mine was about a hundred for a foo t of double stainless. The intake and exhaust are in the same tube and the stuff is super pricey. I bought a Rheem and loved it. I used a kit very similar to this it’s nice when mounted on an exterior wall. https://www.lowes.com/pd/Rinnai-Tankless-Gas-5-in-Steel-Water-Heater-Vent-Kit/1000237223

Duck Duck Grey Duck FTMFW! > Galileo Humpkins (aka MC Clap Yo Handz)
06/10/2019 at 23:22

We have a Rheem. Seems to work pretty well. It came with the house. Been there I think at least 8 years.

Duck Duck Grey Duck FTMFW! > Deal Killer - Powered by Focus
06/10/2019 at 23:23

Wait what is the yearly maintenance? I have one and have never done anything.

SilentButNotReallyDeadly...killed by G/O Media > Galileo Humpkins (aka MC Clap Yo Handz)
06/10/2019 at 23:36

In Oz, most of the tankless (we call them instantaneous) water heaters are either Rinnai or Bosch.

Ours is a Bosch that uses LPG (you call it Propane) as the heat source. It works and doesn’t use much gas compared to a gas boosted tank heater. And yet I can’t wait to be rid of it...

Kinja'd!!!

Primarily because it doesn’t like our low flow gravity fed water supply and is very picky about when it will turn on and off.

But also because we have very adequate sunshine and grid connected solar electric panels.

The excess power generated by the panels is fed back into the grid and we get 8 cents per kilowatt hour for it. If we buy electricity from the grid we pay 28 cents per kilowatt hour. It would be better if that excess solar power was diverted into making lots of hot water first. Or we could just get the sun to heat our water directly as we did at the last house...

Water&EnergyConsulting > Galileo Humpkins (aka MC Clap Yo Handz)
06/11/2019 at 00:35

Noritz. Hands down.

HammerheadFistpunch > Galileo Humpkins (aka MC Clap Yo Handz)
06/11/2019 at 01:37

we’ve got 2 naviens at they’ve been pretty good. No problem with water supply.

PlumberSoCal > RutRut
06/11/2019 at 02:01

I’m a plumber and replaced ours last year with a Noritz. Very happy with it. For tanks I recommend A.O. Smith. $10 an inch? I'm not charging enough!

Variance > gmporschenut also a fan of hondas
06/11/2019 at 03:09

My info is a few years old, so it might be out of date, but since nobody else has replied to you yet...

My understanding is that most of the electric ones aren’t quite powerful enough to adequately heat the water at average flow rates or above. The ones that do absolutely gobble up power, and may require an additional service drop from your mains (unless you happen to have 100+ amps available o n your existing service drop and panel ). For perspective, electric stoves are normally wired with ~50 amp breakers, so imagine how much power something meant to instantaneously heat water to ~120°F would need.

PartyPooper2012 > Galileo Humpkins (aka MC Clap Yo Handz)
06/11/2019 at 06:30

I have rheem. Runs like a champ. I don’t have hard water so there is no buildup. I tried cleaning and nothing came out. Filter was a bit dirty but a quick rinse and you’re done.

I had an issue with condensation. The pump the water goes into grew some algae and it clogged up the purge line. Blew it out with an air compressor and that was fixed. I think the way my line is routed up through the ceiling and into a washing machine drain. If i had a shorter run with less rise, it might not have been as big an issue, but it’s’ something to mind.

Django Fett BR549 > Galileo Humpkins (aka MC Clap Yo Handz)
06/11/2019 at 07:29

I’m a remodeling contractor, and I put the Rinnai 11 gpm unit in my own home last year. From my own research, I had already decided that was the one I likely wanted, then once I spoke to my plumber, he verified my opinion. That's the only brand he will install. We built an apartment for my mother in law in the basement, and with 5 people (including 2 teenagers), 4 bathrooms, 2 kitchens, and 2 laundry rooms, we've never lacked for hot water. And so far have had zero issues with the unit

Aaron > gettingoldercarguy
06/11/2019 at 07:30

I’ m removing a fairly new hybrid and installing gas unit.... hybrid heat pump unit is very pricy and only good for limited application as it will pump massive amounts of cold air into where ever you place it....you can turn the heat pump part off but then you have a very inefficient electric unit....my opinion.....go with a condensing gas tanked unit

Aaron > Aaron
06/11/2019 at 07:47

Also don’t forget the additional heating cost by your furnace or equivalent in winter months from the cold being pumped from the water to the air in your home....my place has hybrid heat pump water heater and central heat pump....Ive found it to be wreckless on power bills....my only concern of tankless units is scaling and poor performance on low/high flow usage

DryGravyTrain > Deal Killer - Powered by Focus
06/11/2019 at 09:32

Thi s is a common mis conception. Both tank and tankless require similar service, draining/flushing.

I just did this to my tankless it cost me like $ 50 for a pump, two hoses and a bucket, you run some vinegar through it for an hour and you are done. Depending on your water, it's a yearly thing. Not hard or time consuming.

Tank heaters should flushed and drained as well to maintain them , and some have anode rods that need replaced occasionally.

Galileo Humpkins (aka MC Clap Yo Handz) > Django Fett BR549
06/11/2019 at 10:13

That’s the unit I’m leaning towards if we do go tankless. Seems to have the most positive feedback.

Galileo Humpkins (aka MC Clap Yo Handz) > PartyPooper2012
06/11/2019 at 10:15

That’s a minor concern I have is that we have hard water in Chicago, so it will require at least yearly cleaning. But from what I’ve seen, it doesn’t seem like it’ll be much of an issue so long as it’s done properly and when it should be.

Galileo Humpkins (aka MC Clap Yo Handz) > HammerheadFistpunch
06/11/2019 at 10:18

I’ll look into that, didn’t see them in my brief research yesterday.

Galileo Humpkins (aka MC Clap Yo Handz) > SilentButNotReallyDeadly...killed by G/O Media
06/11/2019 at 10:21

Picky about when it works in terms of how open you set your faucet or whatnot? I’ve seen that a lot of people have that issue with various models/makes.

Galileo Humpkins (aka MC Clap Yo Handz) > The Snowman
06/11/2019 at 10:23

That’s going to be a point of consideration, our utility closet is 100% interior, but neither of the walls where it would most likely go are too far from an exterior wall.

Galileo Humpkins (aka MC Clap Yo Handz) > RedBaron134
06/11/2019 at 10:26

Interesting. Our regular plumber is coming today for a whole different issue so they’re going to be the first people I speak with regarding install. I knew it could be expensive, but it seemed like that price was high, to say the least.

Galileo Humpkins (aka MC Clap Yo Handz) > Just_jr
06/11/2019 at 10:28

I’ll add those to the list and see what I can find out. Thanks.

Galileo Humpkins (aka MC Clap Yo Handz) > Plumbpros
06/11/2019 at 10:30

I was wondering about the built in recirculating pump. Seems to me that would increase the need for cleaning/maintenance, right? And wouldn’t that require additional install labor for the return lines?

Galileo Humpkins (aka MC Clap Yo Handz) > Texas Plumber
06/11/2019 at 10:31

It’s been recommended by others so I’m going to add that to the list. Seems like people are happy with the 240A.

Galileo Humpkins (aka MC Clap Yo Handz) > BaconSandwich is tasty.
06/11/2019 at 10:34

I’ve read about people with various makes/models having that issue with only having the faucet partly open and the temps being inconsistent. My mother-in-law has two in her home and I can’t say I’ve ever noticed that issue with hers. The issue I’ve noticed at her place is that her water doesn’t seem to get very hot, but that could be due to her changing the settings lower or something else.

Galileo Humpkins (aka MC Clap Yo Handz) > gettingoldercarguy
06/11/2019 at 10:37

Thanks. Our plumber is coming today for a different issue, so I’m going to start by talking to him about install and then go from there. I’m pretty sure our providers have a number of possible rebates, they do for pretty much everything.

Galileo Humpkins (aka MC Clap Yo Handz) > Fuckkinja
06/11/2019 at 10:39

Propane isn’t an option, so no worries there. It’s going to be natural gas. Sucks about the surge, but really that could happen to anything.

Galileo Humpkins (aka MC Clap Yo Handz) > gettingoldercarguy
06/11/2019 at 10:40

That’s easy enough, we already have to do that with our washing machine, and clean out the filter in our dishwasher, and of course our hvac filters. So just add it to the list I guess.

Ready for an adventure! > Galileo Humpkins (aka MC Clap Yo Handz)
06/11/2019 at 10:51

We have a Takata and a Rheem, both natural gas fired . The Takata is 14 years old and going strong, we use it for out potable water. The Rheem is 3 years old because I HAD a Takata for my radiant heat source and never descaled it, so it failed.Replaced it with a Rheem because wanted a heater that I could go to Menarrrrd’s and get a replacement if needed.

I use Haymaker descaling solution on both of them yearly now and have had no problems. Guests LOVE the infinite hot water for showers, and I love the energy savings. It’s in a cabin in Northern Michigan and our worst heat bill was $200.00 a month for a huge ass house with a wall of windows to look out of. That’s about 10% less $ than our well insulated Ranch house was for the same time period. Sounds like you have it figured out.

Mid Engine > Galileo Humpkins (aka MC Clap Yo Handz)
06/11/2019 at 11:09

https://www.homedepot.com/p/Westinghouse-11-GPM-High-Efficiency-Natural-Gas-Tankless-Water-Heater-with-Built-In-Recirculation-and-Pump-WGRGHNG199/300358962?keyword=WGRGHNG199&semanticToken=20330000011_996341532251935_xwgr+20330000011+%3E++st%3A%7Bwgrghng199%7D%3Ast+cnn%3A%7B0%3A0%7D+cnr%3A%7B7%3A0%7D+cn1%3A%7B5%3A0%7D+cnd%3A%7B6%3A0%7D+f%3A%7Bb%7D+cnv%3A%7B0%3A0%7D+vc%3A%7B1%7D+oos%3A%7B0%3A1%7D+dln%3A%7B562248%7D+qu%3A%7Bwgrghng199%7D%3Aqu

Kinja'd!!!

This guy is a beast, not the cheapest but it has been great for us.

Galileo Humpkins (aka MC Clap Yo Handz) > Mid Engine
06/11/2019 at 11:28

Pricing is comparable to Rheem and Rinnai. I’ll add that to the list, thanks. I didn’t even see it come up when I was searching yesterday.

Galileo Humpkins (aka MC Clap Yo Handz) > Ready for an adventure!
06/11/2019 at 11:34

Thanks for that info, that’s good to know as there will be some similarities between Illinois and Michigan. Our hard water will certainly require descaling/maintenance, but we already have a number of things that require minor upkeep so I’ll just add it to my list.

That’s kind of why I’m looking at readily available units, in case of emergency replacement it will be easy to get.

CarsofFortLangley - Oppo Forever > Galileo Humpkins (aka MC Clap Yo Handz)
06/11/2019 at 12:16

6000 views lol

whatisthatsound > Galileo Humpkins (aka MC Clap Yo Handz)
06/11/2019 at 12:36

I use intelli-hot in 2 houses. The system currently in use supplies heat to 3 zones for our concrete floor heating, can run the appliances and shower. I’m a huge fan. Here is our setup, granted I don’t think you’ll need something this big.

Kinja'd!!!

Fuckkinja > Galileo Humpkins (aka MC Clap Yo Handz)
06/11/2019 at 12:44

With natural gas available tankless is the way to go for sure. I much prefer living in the country now. Propane is our only option now.

Check out models with a circulation pump. As an option it’s nice to have hot water immediately. I was to cheap to leave the pump on all of the time though.

Galileo Humpkins (aka MC Clap Yo Handz) > Fuckkinja
06/11/2019 at 14:33

I’ve been only looking at models with the recirculation pump now. Seems like it’s worth the bit of extra $ up front (to us anyway).

Galileo Humpkins (aka MC Clap Yo Handz) > whatisthatsound
06/11/2019 at 14:34

Do we need something that big? No. Are we shopping for one that is bigger than we need? Yes.

Galileo Humpkins (aka MC Clap Yo Handz) > CarsofFortLangley - Oppo Forever
06/11/2019 at 14:35

I guess water heaters are interesting topics?

gettingoldercarguy > Galileo Humpkins (aka MC Clap Yo Handz)
06/11/2019 at 15:23

I’m amazed at reviews from people whose vacuums fail and then admit they did ’t clean the filter.

I remember along time ago at colleague who was an ex pat from the UK yelling at someone over the phone “The car doesn’t just run itself! You have to check the bloody oil! ”

SilentButNotReallyDeadly...killed by G/O Media > Galileo Humpkins (aka MC Clap Yo Handz)
06/11/2019 at 18:25

Yep. That's it. We can get a low flow model that is better suited to our water pressure but we don't think we'll bother.

MikeMc > Galileo Humpkins (aka MC Clap Yo Handz)
06/11/2019 at 18:51

I’ m a Pluming Contractor in Wa State and I’ve installed all 3 and and they all work fine. They each have their own thing that makes them unique but they're pretty much the same. I’ve installed Noritz the most and that’s only because the place I do most of my business sells that brand. However, if a customer requests a specific brand, model#, etc. I’m happy to accommodate. One brand you might be overlooking is Navien. I’ve installed plenty of those over the years too. Navien is just as good and slightly cheaper. Generally when I give bids, I give 2 choices...Noritz and Navien. I’m currently building my own home and I’m installing 2 Naviens NPE-240ANG tankless water heaters.

whatisthatsound > Galileo Humpkins (aka MC Clap Yo Handz)
06/11/2019 at 19:03

I seriously can heat an 1800 sqft house ( it is my only heat) and run dishwasher and washer and shower.

Josh Mills > Galileo Humpkins (aka MC Clap Yo Handz)
06/11/2019 at 20:37

I sell Rinnai and Noritz.

Go with a Rinnai RU199IN, best heater money can buy. I just put this heater in my house.

GI’ve me a call I’ll sell you one at a good price and ship it to you. 941-358-0816

The Real Life Mike Lowrey > Galileo Humpkins (aka MC Clap Yo Handz)
06/11/2019 at 23:54

Food for thought, not intended to persuade/dissuade: our water heater tank was recently replaced and we get much more hot (much more in terms of temp and volume) water now. The last one was old, rusty and ill-maintained. It’s a 40-gal Rheem and we can take showers back to back no problem. Probably not the marathon showers you take but if I wanted to towel off and then hop back in, I could. Point being: a replacement 50-gal tank for you might be good enough of an upgrade

Galileo Humpkins (aka MC Clap Yo Handz) > The Real Life Mike Lowrey
06/12/2019 at 10:13

Trust me, they aren’t marathons Mike.

Galileo Humpkins (aka MC Clap Yo Handz) > Josh Mills
06/12/2019 at 10:18

My wife pulled the trigger on the RUR199iN yesterday. After talking to a few people for install quotes though, I am a little concerned. One guy said he wouldn’t even do it since we have 1" fittings, something about the conversion kits and loss of water pressure upstairs as well as the potential for irreparable damage to the unit that they would then be on the hook to replace. So...thoughts?

Galileo Humpkins (aka MC Clap Yo Handz) > MikeMc
06/12/2019 at 10:21

Navien, as it turns out, is what my MIL’s are. My wife pulled the trigger yesterday on a Rianni RUR199iN yesterday. After talking to a few people for install quotes though, I am a little concerned. One guy said he wouldn’t even do it since we have 1" fittings, something about the conversion kits and loss of water pressure upstairs as well as the potential for irreparable damage to the unit that they would then be on the hook to replace. Then another guy I spoke to said we should get two. So...any thoughts or input on that ?

Galileo Humpkins (aka MC Clap Yo Handz) > Django Fett BR549
06/12/2019 at 13:34

The Real Life Mike Lowrey > Galileo Humpkins (aka MC Clap Yo Handz)
06/12/2019 at 13:48

But you said, “Our only thing is we prefer to have very hot water, for long periods of time and our current 50 Gallon tank doesn’t cut it.” One could infer that, in shower terms, these are marathon showers.

Kinja'd!!!

Galileo Humpkins (aka MC Clap Yo Handz) > The Real Life Mike Lowrey
06/12/2019 at 19:19

Fair enough.

Django Fett BR549 > RutRut
06/13/2019 at 21:20

That sounds far, far too high, even for the concentric vent pipe. Codes vary in some areas, but I went with the non-concentric model & vented it with typical 3" PVC, which is only maybe $1-1.25 a FOOT most places

Django Fett BR549 > Deal Killer - Powered by Focus
06/13/2019 at 21:25

The yearly maintenance is simply descaling, which takes about 10 minutes. Opinions vary of course, but mine is that is a very small trade-off for the significant (for my situation) benefits

Django Fett BR549 > Galileo Humpkins (aka MC Clap Yo Handz)
06/13/2019 at 22:01

Which of your fittings are 1"? Gas or water? On the gas, you likely want a 1" main, depending on the other gas appliances you have. O n the water it’s a little more complex to answer without being able to see your specific situation. And even then, while I have a pretty good general knowledge about plumbing, once you get into proper sizing & flow rates, I’m out of my wheelhouse.

We upped our gas main to 1" to handle the extra demand - we went from only having a gas pack on the HVAC to adding not only the tankless water heater, but also two 6 burner gas ranges. And any of the 11gpm tankless unit draw a LOT of gas when in use, so in the case of your gas main, bigger is likely better.

On the water side, it gets more complex, and there’s no one “right” answer. You get into pressure vs flow vs head loss, and it becomes a balancing act. A 3/4" main going into 1/2" branch lines is the most common installation & is sufficient for many applications. But in our case we have 3/4" branch lines & only step down to 1/2" when we go through the floor/wall to the fixture. That way we have very minimal pressure & volume loss if multiple fixtures are in use at once. The trade-off to that is a 3/4" pipe holds nearly twice the water that a 1/2" does, so it takes longer for the hot water to get to the fixture if it is a long way from the heater.

Bottom line is, I’d get a couple of more installation bids from local reputable plumbers, and try to seek out some that are experienced in tankless units. In my experience (in all of contracting, not just in plumbing), often guys are uncomfortable with anything that’s different than w hat they’ve been doing for years & years

Django Fett BR549 > Deal Killer - Powered by Focus
06/13/2019 at 22:12

And incidentally, tank water heaters require yearly maintenance too - once a year (or more in areas with hard water), you need to hook up a garden hose to the tank drain at the bottom and drain out some water un til there is no visible sediment coming out. Too much sediment in the bottom of the tank will accelerate tank corrosion, and in the case of gas units, will increase recovery time to reheat the water

Django Fett BR549 > BaconSandwich is tasty.
06/13/2019 at 22:23

If you’re having this type of issue, you might try adjusting the thermostat a little lower on the water heater. This sounds counter-intuitive to most people, but the way tankless units work, this will usually at least help.

A tankless unit is either “on” or it’s “off” - there’s no tank of already-hot water to draw a trickle out of. So they have a flow sensor that kicks the unit on when it senses enough flow through a hot tap, and with a hot tap on partially, you can get right in that zone were there just enough flow for the unit to cycle on & off, causing that inconsistant temperature.

So if you turn the thermostat down a bit, you’ll need to turn the tap on a little more for the same amount of "hot", which should help keep the flow sensor in the "on" position.

BaconSandwich is tasty. > Django Fett BR549
06/13/2019 at 23:10

Certainly worth a shot!

Galileo Humpkins (aka MC Clap Yo Handz) > Django Fett BR549
06/14/2019 at 11:54

Gas is 1/2" and Water is 1" main. I don’t think they were concerned so much about the gas, it was mainly the water line the one guy seemed concerned about. Now, all I know I can see are the lines coming into that particular utility closet, so I’m not sure about sizes elsewhere. If I had to guess, based on prior experiences in this home, the builders cut some corners in some areas. If that applies to the rest of the pipe runs, etc, I have no clue.

I’ve reached out to multiple pros, as a best practice regardless, so we’ll see what they all say. The guy who, clearly, did not want to mess with it was from DRF, the Home Depot sub-contracted installer.

Galileo Humpkins (aka MC Clap Yo Handz) > Django Fett BR549
06/14/2019 at 12:30

I went and looked again and I was incorrect , the gas main is 3/4", it’s converted down to 1/2" to the water heater because that’s the size hookup the current water heater has.