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Tankless water heater...

cnaughtin's picture

I am looking at replacing my existing gas water heater with a tankless model because I hate wasting energy holding all that hot water. We have a 1500 sq. foot house with 2 adults and one child sharing 2 1/2 baths. We don't shower at the same time and do not necessarily need to use more than one hot water application at any one time.

What is your general opinion of tankless hot water heaters?

Do you have any particular brand or type that you recommend?

I appreciate any advice that you could offer!

- Colin

(post #77026, reply #1 of 15)

I am also curious as to the performance of tankless systems with hard water.  I've heard that problems can result shortly after installation because of the intense heat used in the small tubing.

Is there any truth in this?  All I've heard is third-hand info.


(post #77026, reply #2 of 15)

I bought and installed a Paloma from -

Model PH-28RIFSN - 199,000 btu

Moved in the house almost a year ago and never regreted any part of the effort or expense.

Effort - No more than a conventional tank water heater

Expense - about double

I put in a LP unit, external surface mount, ran 1" black iron gas pipe to feed the hungry unit - burns a lot of fuel while running but is more efficient per unit heated and there's no standing pilot or tank to maintain the temp for while it's sitting - in other words - save a lot of $ long term and enjoy never ending hotwater when in use.

I also wired mine to a standard heavy duty power cord and connected it to a computer battery backup. The unit uses an electric source primarily to control the electronics that control water temp and firing. I figured with electronics involved it would be a good idea to protect them from surges. Also brief power blips during a shower won't end up dowsing you with cold water. The externally mounted unit comes with a 200w heat panel to prevent freezing in extreme temparatures so be sure and size your UPS accordingly. I used a 650 va. Large enough to finish a shower when the outside temp is well below freezing.

They also sell a flush mount external kit. Personally I love the fact that all combustion takes place outside the house versus an internal vented unit. If I were in a northern climate I'd use the flush mount kit but here in central North Carolina, the temps are moderate enough to simply mount the unit right on the wall outside.

On tough days after working outside in the yard cutting wood and such, I can start the Whirlpool to filling, step in the connected shower and use both valves/dual heads. About the time I'm finished showering the insulated tub is full. My wife even ran the dishwasher one time while I was doing this. No loss in temp but I did lose some pressure. No big deal.


Pedro - Stubborn Old Mule


"What you leave behind is not what is engraved in stone monuments, but what is woven into the lives of others."

(post #77026, reply #3 of 15)

Pedro -

Thanks for taking the time to provide so much info! Very informative!

- Colin

(post #77026, reply #6 of 15)

Hi Colin,


From everything I hear, tankless heaters should last about twice as long as a tank unit because you don't have sediment eating away the bottom of a tank and no corrosion settling in. That should also help pay for itself if you plan to be in your home a long time.


My primary excuse in buying the unit was having to take a shower after my teenage daughter emptied the "tank".


My justification was that it would pay for itself in time and would also burn less fuel contributing to being less harmful to the environment. Personally I'm not an avid tree hugger but anything that saves on the planet and makes my life immediately better is a no brainer.


The only two things I've ever been able to dig up negative is the half second or so that it takes for the unit to fire, it senses water flow to automatically turn on, and the second and a half it takes to start producing hot water. Big deal!


The other thing is on long runs you can't practically run a recirculating pump but few houses are built with that feature anyhow. Of course, you can always solve that problem by either locating an on demand electric unit at sinks for instant hot water and a long usage would then allow gas heated water to take over. Another option would be to set up a recirculating pump to a two gallon electric water heater near the tankless unit. That would keep hot water at each faucet and minimize tank off heating.


I actually installed two levered faucets instead of single lever. Virtually all hand washing is done with cold water. Single levers have a bad habit of getting flipped on with both hot and cold flow firing up the water heater just long enough for you to rinse your hands and turn it off before it gets warm wasting flow of hot water in the supply line.


The unit also comes with a digital thermostat. I installed ours next to the dishwasher where we crank it up to 120. Otherwise we leave it around 108-110 for showers and such. It has a safety feature that will only allow a 4 degree rise if it's alreay running. Someone starting a load of dishes can't accidentally scald someone who's already in the shower.


Lots of details but I love this tankless thing.....first hot shower since birthing a teenager hehehehe!


Pedro - Stubborn Old Mule


"What you leave behind is not what is engraved in stone monuments, but what is woven into the lives of others."

(post #77026, reply #4 of 15)

There are several "SEARCH" fields about this web page.  Type in "tankless heaters" and see how many terabytes have been dedicated to the subject!


(post #77026, reply #5 of 15)

A couple things i've learned:

The replacement remote control for the Rinnnai units costs about $200. You can't adjust the temperature without it and you have to have one to diagnose any ills in the thing.

I put in a Aquastar a few years ago, with hard well water. It's still working fine, but i wouldn't buy one with a standing pilot again.

I just put in a Seisco tankless electric for space heating. It's only had one day running, but it's very tidy, no remote to disappear. I'll be interested to see how the bills compare to LP used previously.

(post #77026, reply #7 of 15)

I look forward to hearing about your difference in cost to operate an electric unit. Electricity here is reasonable and doesn't fluctuate seasonally as does gas.

I have gas logs, gas cooking and the tankless unit - LP -

I bought a big tank that I fill in June when cost is the lowest.

It pays to shop around when doing this. My first time doing this, Ferrell Gas wanted some long contract. Without the contract they wanted double the price of Dixie Denning, and yes I did double check to make sure the gal on the phone knew I owned my own tank - she said they charge more for self owned tanks because they have to inspect them, oh and they don't inspect "their" tanks????

Crazy people in this world.

Pedro - Still A Stubborn Old Mule


"What you leave behind is not what is engraved in stone monuments, but what is woven into the lives of others."

(post #77026, reply #8 of 15)

I put this electric unit in for a friend, waiting to see how it goes bec i'm thinking of using the unit myself, using the same reasoning as you about electric costs fluctuating less. I figured out with an 85% efficient LP gas unit, LP only needed to hit $2/gal to be even with electric; it's gotten to $1.95 already.

I also just paid $$$ to have my tank refilled from empty. A slow leak on the filler fitting on the company-owned tank was part of the problem, but they offered no recompense, only repaired it. With tank rental at $60/year, and the damage the trucks have done to my drive when it's boggy in spring...electric is starting to look good, though i never imagined i'd say that. No stack losses, put the unit anywhere you feel like it...i hope the numbers work out as well as it sounds on paper!

(post #77026, reply #9 of 15)

Don't get me wrong, I'm not opposed to an electric unit at all but.......

I enjoy working hard - normally to the point of injury and filling the whirlpool "while" taking a dual headed shower is therapeutic - will the electric unit you've worked with handle this task? I'd gladly pay $3 a gallon for this one feature - much over that and I'd switch to a wood fired heated tank - neighbor down the street has one - he puts tree trunks in it during the winter and opens the windows in his upstairs to let some heat out - takes care of his hot water and heating needs - yes, his unit is way over sized and very wasteful - hmmmm maybe I could run an insulated pipe from his house to mine...

We had a weird but mostly mild winter - speculation is for LP to run about $1.75 in June - we'll see.

I'm also an untrained top notch country chef - now there's an oxymoron - no self respecting cook would consider cost an issue when comparing gas to electric cooking, of course cooking takes minimal gas.

One other issue - I'm working out the details on building a small weekend cabin - no way to get electricity in and the spring doesn't generate enough flow to produce electricity. I'm considering using marine batteries to run LED lights and a small water pump to keep a small water tower full from the spring. I could then use propane to cook with and heat water. The water heater would be a tankless single user version and I could run the electronics off of an old computer ups tapped into the marine batteries. I figure two marine batteries should actually get me a full week of use. I could bring them back and recharge them at home. I'd probably use one battery at the time, that way I'd only have to tote one if that's all I used. I starting a new thread here?

Pedro - I'm still a stubborn old mule - I remind myself of House....M.D.


"What you leave behind is not what is engraved in stone monuments, but what is woven into the lives of others."

(post #77026, reply #10 of 15)

The unit i used was an SH-18, used for space heating. The "18" denotes the kilowatts. They make other models used for DHW prefaced with an "RA" before the kilowatt number, though i'm not sure what the internal differences are as they appear similar with the covers off. Maybe the temp range is different - this is selectable on the SH - but i don't know for sure.

But in answer to your question about supplying enough HW....boy, howdy, this one surely would. It was supplying three zones at once with water hot enough i couldn't hold my hand on any of the three pumps, through 3/4" piping off a 1" manifold.

Here's a page ( from the Seisco website talking about heat output among the various models. Lots of great info on that site. You can drill down to installation and trouble shooting, even.

One of the things i do when i intend to spend a lot of money is go to forums looking for problems with the items. If a lot of people are frustrated, i don't buy. In the only cases i found people had trouble - the brain boards on a few examples about two years ago had troubles - the company promptly sent out new boards to the customer with quibbling and the customers were very pleased with the prompt attention they received.

I asked my local supplier if they'd had any problems with this aspect of the boilers. They said they've sold at least 200 in the last year and not received a single complaint, only laudatory comments.

The Seisco site only sells DHW heaters, not the space heaters. I noodled the web looking for deals for the SH model and found "Energy Supermarket" had them for $100 less than through my local supplier, but my local guys could get it sooner so i went with them at $833.

However, and this might be a consideration at your cabin, you apparently can't get the energy rebate on an electric model, though you can a gas one. Takagi makes a "T-K Jr" model which i see that Energy Supermarket is selling that one at $553 - with a $300 rebate, it's a steal. (

Mind you, i've never researched that particular model (nor the fine print in the rebate!), but the Takagis have a good rep. If you'll have gas available there anyway, this might be the way to go. Lugging batteries back and forth... <shudder>

(post #77026, reply #11 of 15)

Be careful when looking at "marine" batteries.  Many are not true deep-cycle but are considered dual Start/Deep-Cycle.

I would suggest that you look into a pair of 6v golf cart batteries wired together to provide 12v.  Then a small solar panel to keep them charged so you don't have to lug them back and forth.

(post #77026, reply #12 of 15)

"What is your general opinion of tankless hot water heaters?"

I love mine, and we have enjoyed about a 20% savings on natural gas. Hot water will take a tad longer to reach the faucet, however.

"Do you have any particular brand or type that you recommend?"

We bought Noriz. They have a 10 warranty and I got another 10 years from my dealer.



"I may be drunk, but you're crazy, and I'll be sober tomorrow." WC Fields, "Its a Gift" 1934

Regards, Scooter "I may be drunk, but you're crazy, and I'll be sober tomorrow." WC Fields, "Its a Gift" 1934

Tankless Water Heater (post #77026, reply #13 of 15)

As an experienced plumber I can tell you that hot water tanks are my go to.  It is less efficient but easier on the wallet.  If you are green and would like a tankless, Navian seems to be the front runner for single family home installations.  They are a quality product with a great help line to call for anything if there is a problem. It is very important to follow the maufaturers recommendations when servicing the tank.  The parts are expensive to replace and it will break easily, so a yearly flush is highly recommended. If you are in the edmonton area and would like more help with tankless systems, please feel free to contact me at

10 years and no hot water. (post #77026, reply #14 of 15)

If the OP has gone 10 years with no hot water I don't think he needs help now.

Dunno about that -- he's (post #77026, reply #15 of 15)

Dunno about that -- he's probablly really in hot water with his wife by now.

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville