Recommendations on tankless NG water heater please

[blinn]

We built our house 21 years ago and my first gas water heater ruptured today. I'm thinking of going tankless this time. My current system is 2 55 gallon gas units in series with a full house recycling pump that has a 24 hour timer. Here are my questions:

What brand is the best or do you guys have good (or bad!) experiences with?

What should I expect to pay for installation?

Do I need to loose my recycling pump? I would think that the on demand design would never turn off if a pump was on.

What size will we need, we have 5 bathrooms but there is just me and my wife in the house.

Thanks for your help!!


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[Adk Mike]

You need a little system design help. Something your not going to get on here. It just sounds like you need somebody that can figure out the system. You need to get the recovery necessary for what your doing figured out. It's called first hour recovery.The tankless water heaters are great. But they're not for every application. They are best when space saving is needed. Tank units take up floor space.
I like Bradford White tank style when I have the room. The brand the plumbing trade uses.
That being said the the most popular tankless is a Rinnai. They are very good and can be installed in series if needed. Mike

 

[mbatarga]

- I don't think you can use tankless with the recycling pump
- tankless is going to require an increase in your natural gas line piping size (most likely)

https://www.rinnai.us/residential-product-finder

 

[Jackfre]

I'm biased as I have worked with Rinnai since '91. That said, they make excellent equipment. For you situation in a large house, I'd suggest the RUR model. That is a 199,000 btu unit. It comes with the recirculating pump built in. As well, with the addition of the optional wireless module you can have "on-demand recirc". There are wireless motion sensors and push buttons, that can be mounted in the M Bath and kitchen. The motion sensor will pick up your presence and make the pump. When the return water is within 15* of the set point temp the circ turns off. The wireless push button goes in the kitchen. At a 70* temp rise the RUR will make about 5.6 gpm.

With 5 baths, how is the system piped and how far from the water heater is the kitchen and M Bath?

 

[blinn]

Jackfre,
Our Master bath is one of the closest taps from the tank but the kitchen and laundry room are on the other side of the house! When the recirculating pump is not on it probably takes a good 3 minutes for hot water. The piping is a home run that goes back to the tank, is that what you mean?



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[Pate]

I had a Navien Combo installed when me house was built a few years ago. I had one sensor go bad last year. Sensor was covered, but labor wasn't.

 

[blinn]

Just noticed something that I don't understand. I turned the valve going to the hot water tanks off until we can get them replaced. The cold water works fine at all the sinks but we have no water in the showers. Why wouldn't it just run cold water in the showers?


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[Platonic Solid]

3-bed, 3 bath, 2 adult household. I had a Rinnai R75LSi installed in 2011 for $3400. Prior water heater was electric tank type. Getting rid of the electric water heater literally cut my electric bill in half. I don't have natural gas available so it's running on propane - I believe the unit can run on either. Two down sides are:
1. It takes longer to get hot water. It's not so inconvenient that I'd be willing to waste energy heating water in the pipes via recirculation.
2. I have well water and have to do the 1 hour flush, a mix of mostly vinegar and a little CLR, 3 times a year to remove lime and scale. If I don't, the impeller won't rotate to indicate hot water demand and the unit won't fire.

 

[wssix99]

Do I need to loose my recycling pump? I would think that the on demand design would never turn off if a pump was on.

Kinda. You can still use a recycling pump, but you'll need one with an adjustable thermostat shutoff. See this thread and post #23 for the specifics:

https://www.garagejournal.com/forum/showthread.php?t=360690&highlight=pump

Depending on the location of your water heater, the size of your pipes, the length of the runs, etc. you may or may not need the recirculating pump. I designed our system so that the heater is in the middle of the house, on the middle floor, with equal runs to all the appliances. However, the plumber used some 1" lines to combat pressure drop and it contains such a volume of water that I needed the re-circulation to have hot water in a reasonable amount of time on those lines. You'll also want to use a timer other type of shut-off with it.

What size will we need, we have 5 bathrooms but there is just me and my wife in the house.

You'll need some engineering help from a HVAC pro, but our unit takes the place of a 100+ gal tank, so they come in very large sizes these days.


More food for thought. These require a great deal of maintenance yearly. They have to be descaled and have a bunch of filters cleaned. If you do it yourself, it' ruins one afternoon every year. If you pay someone else to do it for you, you may loose a lot of money you would save over a conventional system.

Another option you might look at is an electronic heat pump model.

 

[Jackfre]

Your shower valves are pressure balance valves. No hot or cold to the valve yields no water. What size pipe feeds the kitchen area? What size is your hot water return line? Do you have a basement or crawl space or are you on a slab? Let's analyze the system prior to making any major decisions. Putting a time or temp control on a tankless is a good way to kill it. The on- demand system I described is absolutely the best on tankless for energy, water consumption, which is a big deal here in CA, and durability of the new tankless.
I installed a Rinnai in my home in MA in '99. It was a pre-production unit that I had to replace for the sale of the home in'11. Upon removal I took my Sawz-all and cut it in half. It was as clean as a whistle. I never touched that unit in 12 years and it was still running perfectly when removed. Why did I not have to flush it 3X/yr? Water quality. If your original tank lasted 20 yrs you should be in good shape, but you should have your water tested to see what you have. If you are on city water the town will send you a water analysis. Make sure the one they send you is the one that feeds your section of town. Believe me, that is important. Flushing a unit 3X a yr means that all the rest of the plumbing system is getting knocked too. The water for the home should be treated. If it is necessary to clean inlet filters regularly, you have dirty supply water and a whole house water filter should be used on the cold supply entering the home. Tankless are absolutely different from tanks. What is necessary to get the return on the investment and to get the comfort you desire and deserve is to understand the units, your homes pipe system, your needs and install the unit to operate optimally. Check a few things out and get back to us.

 

[alexb2000]

I have a Rinnai and love it. My wife takes long baths, no more hearing about running out of hot water. If we both have to get ready at the same time, no problem, plenty of hot water. Guests come and the house is heavily used zero worries about running out. Last, when we travel its really nice to burn zero gas while we are away.

I don't ever want to go back to conventional heaters.

 

[yeldogt]

First with just you and you wife -- you don't need two 55 gal tanks running. Are you sure they are not split -- That's how we did our house in pawleys ... One larger did part of the house with a big tub ..and the other smaller finished out the house.

The "on demand" work -- if everything is set up correctly they can work well. In colder climates and with well water where the incoming water temp changes a lot over the year the modulating are a must.

I think you have to look at your overall cost of running the tank units on NG -- with NG the benefit of the tankless is greatly diminished.

Do the recirculation pumps run the whole house? -- I'm trying to understand if you are keeping the water hot to all the bathrooms and fixtures in the house all the time.. If not properly insulated that's bringing in a lot of BTU's.

You do have home runs .. so that should be quicker -- is its a 3/4 pipe?

IMO -- tankless work best when things are close and when they run dedicated bathrooms. when you start doing a big house with lots of variables .. go slow. I have them at the beach .. I'm using a tank with my new build and I have propane .. so that should say something.

With only one pump -- and no valves you would be heating the whole plumbing system each time.

I would think about splitting the systems -- one tank for the baths you use and kitchen w/ pump and the other for the rarely used bathrooms. Simple -- easy .. cheap to run.

 

[blinn]

They are currently joined together in series and the hot water line goes throughout the house and is not zoned. There is no way to alter the configuration, 5500 sq ft. house with 3 floors and no crawl space! Why do you say NG makes tankless less of an option? I thought just the opposite. Yes, the recirc runs the whole house which is why I seldom turn it on with just the 2 of us. When the house is full with company or holidays we do use it though.


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[yeldogt]

They are currently joined together in series and the hot water line goes throughout the house and is not zoned. There is no way to alter the configuration, 5500 sq ft. house with 3 floors and no crawl space! Why do you say NG makes tankless less of an option? I thought just the opposite. Yes, the recirc runs the whole house which is why I seldom turn it on with just the 2 of us. When the house is full with company or holidays we do use it though.


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You mentioned "home run" -- is that for only some spaces ?

The cost to run conventional tanks w/ NG is low ... the tankless made more sense when gas was running 3x current prices. I spend under $25 dollars a month on gas (3 people) -- stove and dryer also. How much can I save? It's not going to be $100 a year -- and for something I don't like?

I think you should review what you have and need -- maybe review if a smaller tank with higher recovery would work. less stand by loss -- but that's small anyway. You could also have two tanks and keep the first one off .. it would act as a buffer tank. Second tank would keep you in hot water .. when guests come .. turn on first tank for capacity. We did this at our ski house -- they were electric .. so running two big tanks for a couple people was expensive and not needed... but. place had many bedrooms ....... so we needed it when place was full.

 

[Showkey]

Tankless
1High install costs
2High maintenance cost ( highly dependent on water quality)
3Long wait for hot water in distant faucets
4Water and sewer and fuel cost may actually go up with a large family use.
5Return on investment might never happen.
6 In most install.....New gas line or electric supply needed $$$$ back to point 1
7 cold climate need large units for adequate temp rise and flow rate for multiple use points at the same time, back to high costs on install. Back to no ROI.

One tank unit sized correctly running NG in some locations may cost $8-15 per month to run and will supply hot water to every faucet in seconds. For a two person house hold that equals almost a continuous supply of hot water witha tank unit. My gas costs are $8 per month.

Read the other tankless posts .......there are dozens and dozens.

 

[terryo1965]

I had a Navien unit installed about 5 years ago. It has worked perfectly, absolutely no issues with the unit. With 2 teenagers at home it's nice to have endless hot water, but I don't really see savings on the gas bill. When it comes time to replace it and the kids are out of the house I will probably go back to a tank unit.

Terry

 

[My Old Tools]

We have two Rinnai units that were installed as new construction in 2006. So far they have been fine. I descaled them last summer. Some low flow devices may not flow enough to trigger them. At our lakehouse remodel we went with Navien and have instant hot water with the built in recirculation. They actually have a small 2 gallon or so tank built in along with the pump. So far we love the instant hot water.

 

[blinn]

Well, plumber came and we talked about all options. Unfortunately the gas supply line is not sufficient to run the 199,000 BTU required. The expense of running that did not make sense so I'm going back with conventional unit. Thank to all for responding!


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[6768rogues]

I would not use a tankless unit with a recycling pump without having a holding tank. It might cause the heater to short cycle. Also, I would not buy a tankless unit that costs 3 to 4 times as much as a conventional unit. It looks like you decided.

 

[Jackfre]

I would not use a tankless unit with a recycling pump without having a holding tank. It might cause the heater to short cycle. Also, I would not buy a tankless unit that costs 3 to 4 times as much as a conventional unit. It looks like you decided.

Perhaps you are not up to date on what is out there. Yes, you can buy a much less efficient tank for less and have less.

 

[wssix99]

I would not use a tankless unit with a recycling pump without having a holding tank. It might cause the heater to short cycle.

Not if you use one with a thermostatic cutoff. (The adjustable speed units caused my Navien to short cycle. When I swapped it for the thermostatic model, all became well. Unfortunately, Navien gave instructions on how to hook these up, but not which type to select...)