building a house and architect is recommending. Will be two of us but three kids and their husbands/wife will visit.

Can tankless keep up with that demand?

Anyone with experience have an opinion of tankless vs traditional heater?

Thank you.

Yes. We have one tankless that replaced two traditional water heaters. They will size it so that it can run every hot water faucet in your home at the same time.

It's the way to go

Have tankless now and in my last house. Will never do anything different ever again. If you want to run 3 showers at the same time, make sure it can support 4 flows (always a bit extra)

Do you have gas?

Yes, gas is the only way to go. Electric's aren't efficient enough.

Had a tankless installed last year. I chose it myself, and had a license plumber install.

This unit is nice: < $1100 and has interface panel that can set the temperature within your home (wired). I've heard mixed reviews on the wifi modules that can be retrofitted.
https://www.tanklessking.com/rheem-rtgh-95dvln-2.html

We have this mounted outside right next to our gas meter, so the install costs was actually reasonable.

We had it installed shortly after we moved into our home, so I didn't have a lot of data points about gas usage before. I will say it gets hot fast, doesn't require much of a flow to activate, and is endless, as one would expect.

If I had to do it again, I would have considered getting an exterior mounted tankless...

When we built, we were spec'd two in series or maybe parallel to support the demand of a 3.5 bath, 4 bedroom. At the new house, we remodeled and installed a single unit. Wouldn't use anything else.

Not even close. We have one for upstairs and one for down.

Water bill likely to be higher, but worth it. Never runs out....

+1 on the Navien and recirculate line. Endless hot water is nice...instant hot water that is also endless will get you spoiled

I have a Navien in my new house. It is badass. The instant hot water revolutionizes things.

We just installed one in a home we remodeled. We also did the recirculating line and it is awesome. The heater itself is on the opposite side of the home from the kitchen and it is nice to turn the faucet in the kitchen and having near instant hot water.

I think that over time it will be cheaper than typical hot water tank because of the reduced gas consumption and the reduced water required waiting on the hot water to heat up.

Only thing I don't understand about Navien: why are reviews and owner feedback so hard to come by online?

Heck, I just did another search to make sure I'm not crazy. So little can be found from forums, rankings, etc. takagi, rinnai, rheem, Bosch, ecoSmart....

I always assumed plumbers recommended them because they are sold through plumbing supply shops and they could make a little extra.

I have a Rinnai brand mounted on the north side of the house with very little protection from the weather. It has operated flawlessly.

Thank you to all of you for your input. Certainly changed my mind. I'll use it as we start construction.

I have 2 Navien tankless water heaters that are 5 years old. They are the only tankless heaters I have owned. In 5 years, we've had small issues with each of them. Fortunately, there is one for each side of the house, so we always have hot water in 1/2 the house when one fails.

If you're handy, the Navien water heaters display and error code when they have a problem and the owners manual has troubleshooting instructions. One time I was able to fix the issue myself. The other time I had to call a plumber. I live in a city of ~140,000 people and there are only 3 plumbing companies listed on the Navien website. If you live in a smaller city, make sure there are technicians for whichever brand you get.

For a different perspective, I installed a Navien 7 years ago in my 4/3, and have never had an error code/problem. I just perform the annual flush.

Also something to consider is a high efficiency/condensing unit vs a regular tankless. It costs a bit more up front, but no expensive hi temp anti-corrosive exhaust pipe is required along with the clearance that entails. A condensing unit uses regular pvc pipe for the exhaust vent, and generates small amounts water/condensate as a byproduct. In theory they are 10-20% more efficient to operate.

By the responses here, I'm going to guess I either have crappy units, a crappy plumber, or both. I've not been happy.

Faucet nearest the tank will take a good 20 seconds to warm. Endless heat after, but 20 sec is forever when you're standing there.

2 units in the attic that serve the house, split between kitchen and master bath and kids rooms/guest bath.

Suggestions?

20 seconds isn't uncommon.

Larger houses have a lot of pipe. And doing a recirc isn't super straight forward in every home. My understanding is that you need to take the hot line from the furthest faucet and feed it back, but I could be wrong.

evan_aggie said:

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20 seconds isn't uncommon.

Larger houses have a lot of pipe. And doing a recirc isn't super straight forward in every home. My understanding is that you need to take the hot line from the furthest faucet and feed it back, but I could be wrong.

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Depends on the design of the piping system. If you have a continuous HW main with branches off to the fixtures, then yes, you will have the return loop from the end of the line to pull the cold HW back into the system so that the HW main is always hot. Recirc loops waste energy because they are heating the water whether you use it or not, but they save on the cold water that you'd normally waste waiting on hot.

Aggietaco said:

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evan_aggie said:

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20 seconds isn't uncommon.

Larger houses have a lot of pipe. And doing a recirc isn't super straight forward in every home. My understanding is that you need to take the hot line from the furthest faucet and feed it back, but I could be wrong.

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Depends on the design of the piping system. If you have a continuous HW main with branches off to the fixtures, then yes, you will have the return loop from the end of the line to pull the cold HW back into the system so that the HW main is always hot. Recirc loops waste energy because they are heating the water whether you use it or not, but they save on the cold water that you'd normally waste waiting on hot.

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I'm pretty sure most have a timer to set so it only runs whenever you typically use shower, kitchen sink, etc.

Better install additional water heater tanks just to be safe

I have two gas water heaters about 25 feet apart in the attic, one for downstairs and one for upstairs I assume. Is it likely I could get away with one tankless to replace them both? Anyone have good or bad feedback?

Depends
Your max simultaneous water usage
Plans to use a recirc pump or
Tolerance for delay before hot water arrives

My neighbors moved their 2 out of the attic during a remodel and went with a tankless. Just make sure it's big enough to fulfill needs.

Rinnai twin propane tankless water heaters located on west wall of our 7 year old house.
Also use a 5 gallon elect water heater, expansion tank and recirculating system.

Zero problems - instant unlimited hot water, fantastic system!

(I also run vinegar through them twice a year to keep the pipes cleaned - get a small pump with washing machine lines and it take about two hours to do this).

Sounds like I need to retrofit with recirculating pumps. Not happy with my plumber for not giving me this option at the outset.

Looks like I'm going to have 2 gently used Rennai tankless for sale. Pretty sure we are going to pull them in favor of ones with recirc pumps.

PFG said:

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Looks like I'm going to have 2 gently used Rennai tankless for sale. Pretty sure we are going to pull them in favor of ones with recirc pumps.

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Can't you just install a separate pump at the furthest fixture?

Everything I have looked into is the pumps found on Amazon cant be used with tankless. Only thing I have seen is rennai offering a retro fit pump, (thermocirc360) but it doesn't list prices. I havent tried calling them so not sure if you have to be a licensed plumber or a distributor to get prices.

PFG said:

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Sounds like I need to retrofit with recirculating pumps. Not happy with my plumber for not giving me this option at the outset.

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Indoor I assume? If not, let me know. Bout to start a renovation.

Interesting. Guess I had an overly simplistic understanding of how they worked. Thought it just pulled water through the hot line after whatever source you use to heat it.

West Texas Lawyer said:

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PFG said:

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Sounds like I need to retrofit with recirculating pumps. Not happy with my plumber for not giving me this option at the outset.

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Indoor I assume? If not, let me know. Bout to start a renovation.

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Yes. Both indoor. Going to be in perfect condition. Attic mounted, 3 months old, rain water only. So naturally soft water running through them.