# Tankless Hot Water System



## Shoes (Apr 12, 2000)

Anyone have experience with a tankless or 'on demand' hot water system? I know they are more expensive to install. I would like to get rid of my 50 gallon tank to get more floor space and use less energy, but I don't know enough about them to make the move.


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## lbrombach (Aug 27, 2007)

A couple years ago, I put one in for a customer of mine (I'm an HVAC guy). Their only complaint was when the water was on and flowing relatively slowy, it would get get real hot, then get cold for a few moments. No trouble in the showers, only when the lady of the house was rinsing dishes. Turns out that because the burners didn't modulate, (they were On or Off only) the water would get too hot when not enough was flowing to absord all the heat. Then the unit would turn off on it's high-temp limit. It would cool down then fire back up. That was a bosch aquastar. They have 2 sizes IIRC, we put in the bigger one made to handle a couple appliances at once. I think the problem would've been minimized if we had installed the smaller unit. Of course, then you couldn't shower and run the dishwasher at once. I don't know how much more they cost, but there are ones out there that have burners that can dial up or down to meet the demand. At least the guy wasn't mad at me, since he chose and bought the unit, and I only installed it.


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## Hawkman (Oct 4, 2004)

I have two Noritz N-063s in my house at each end. The only reason I have two is because the bathrooms are at each end and there was no where on the front or back of the house to vent them. Plenty of hot water. :yikes:

I think there is still tax break for them


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## polarbare21 (Feb 17, 2003)

I've had the Bosch Aquastar for 4 years, we're completely satisfied with it!

Endless hot water for showers, but dont expect to be able to do laundry, run the dishwasher, and Shower at the same time.

Yes there is still a energy credit on your tax form, and my gas bill really dropped!

Good Luck and enjoy!!


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## JimLeadfoot (Dec 16, 2005)

I looked into putting this type of system in the house that I am refinishing - or I was going to put separate units at each (feasible) fixture...

I was advised otherwise by a knowledgeable plumber because my house is on a well system. If the water treatment/softener system does not remove all particulate matter, iron (mostly) and other hardness as well as metals can get into the coils and causes corrosion, buildup, etc. Once this occurs, efficiency is affected as well as the potential for costly repairs. Obviously, damage caused to the unit by quality of the water would be unlikely to be covered under a warranty. Something to think about, but if you have City water, I have heard good things about the units.


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## Hawkman (Oct 4, 2004)

JimLeadfoot said:


> I looked into putting this type of system in the house that I am refinishing - or I was going to put separate units at each (feasible) fixture...
> 
> I was advised otherwise by a knowledgeable plumber because my house is on a well system. If the water treatment/softener system does not remove all particulate matter, iron (mostly) and other hardness as well as metals can get into the coils and causes corrosion, buildup, etc. Once this occurs, efficiency is affected as well as the potential for costly repairs. Obviously, damage caused to the unit by quality of the water would be unlikely to be covered under a warranty. Something to think about, but if you have City water, I have heard good things about the units.


Good Point.... 

Also you need to flush/drain, clean filter ( on the ones I use ) on them every 3 months.


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## Backwoods-Savage (Aug 28, 2005)

Hopefully they have improved these things. Many moons ago we installed one in our house and hated it. We also know of a fellow who installed one in a bakery and he did not have it in 2 weeks before taking it out.

The only problem we had was that after someone showered or drew a lot of hot water, then shut the water off. If someone used water within the next 5 minutes you had to be very careful or your hands would get burned. I do mean burned! The using evidently got awfully hot during use and the water that remained in the unit then super heated while sitting in the unit. 

I do know of one other person who has one and he loves it.


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## stevevdw (Nov 7, 2007)

Take a look at www.noritz.com They are probably the largest provider of these things in the US & there's lots of good info on the site. Be aware that some of these things require stainless steel venting which can add a couple hundred to the price. The B-vent units usually do not modulate & usually are not as efficient. Make sure you pipe in some isolation valves & hose bibbs on either side of the unit so you can pump some CLR or something through the heat exchanger every year or so. I would suggest you get a water sample done & call Noritz with the results & see what they say. If you are replacing an existing tank style make sure your gas piping can handle the demand. Most tank unit burners are around 40 KBTU since they have time to recover. Tankless units will start around 80 KBTU modulate up to 236 KBTU or more. If your gas piping is not large enough the unit will not run correctly. I heard Bosch (aquastar) is coming out with a unit which vents PVC but have not seen it yet. The basic units on the market start around $600 with the big ones going for $1400 or more. Hope this helps.


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## Splitshot (Nov 30, 2000)

Efficiency wise there is little difference, in fact some of the tankless units use more energy because of the much bigger burners.

The savings comes in stand by losses. That is the energy lost as the water in the tank cools. If you install a electronic vent damper and additional insulation there is little if any savings in the tankless water heater over the standard energy efficient water heater.

The one real benefit is if you have a situation like Hawkman where he has long distances from water heater to tap. If you have to wait a long time for hot water, you have extra water and sewer costs for the extra water and after you turn off the hot water, the heat from the water in the pipes is wasted, but only in the summer. In winter this lost heat from the pipes offsets heating costs.

In that situation I would use a circulating pump in winter.


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## stevevdw (Nov 7, 2007)

Splitshot said:


> Efficiency wise there is little difference, in fact some of the tankless units use more energy because of the much bigger burners.
> 
> This may have been true of the old single stage units but the current modulating/condensing units burn anywhere from 12 KBTU to whatever the max is for the unit. Since most tank style units burn 40 KBTU regardless of demand the tankless unit is more efficient.
> 
> ...


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## Splitshot (Nov 30, 2000)

No argument. It is possible to have a reduction in gas usage for the reasons I mentioned, but it still takes 1 btu to heat one lb of water one degree Fahrenheit. If your company is telling people they can reduce their gas bill 30% by installing a tankless water heater I would call that deceptive, kind of like window salespeople telling you that you can save up to 50% of your heating cost by installing new windows.

While that is possible too, it is very unlikely.

It is possible to have that kind of saving if they have electric heat and only use gas for heating hot water or just used summer bills, Sediment build up can affect efficiency, but that is what the spicket at the bottom of the water heater tank is for. Tankless units sell for two or three times the standard water heater and if you noticed I compared it to a standard energy efficient water heater. Those are the ones that use a forced draft fan.

If the tankless unit is a long way from the tap it is not instant either as you still have to wait for the water that has cooled in the pipe to go down the drain. How the manufactures got a tax credit for these units is just a mystery to me, but there are a lot of politics in the energy field.


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## M1Garand (Apr 12, 2006)

With rising gas prices...how do these (and tank units) compare with the electric ones? Is it less to have an electric water heater now? My pilot keeps going out on mine, it's an older heater and probably about time to replace it and I've seen the tankless ones and electric and wondering how they compare.


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## Splitshot (Nov 30, 2000)

Electric heating is always more expensive. If you want to compare follow this example.

In one million btus there are 292 kwh.
Find your cost and multiply it times 292.

For example Consumers is about $.10 per kilowatt hour or $29.20 for a million btus.
Since electric is 100% efficient, that is the cost.

Natural gas including transportation charges is about $1.20 per hundred cubic feet.
A ccf is equal to about 100,000 btus so it takes 10 ccfs to supply a million btus
$1.20 times 10 is equal to $11.20 but the standard water heater is only about 65% efficient. 
Divide $11.20 by 65% and the real cost of 1 million usable btus is about $17.23.

If you use propane, a gallon is equal to about 95,400 btus with the same efficiency as natural gas.

The utility tariff can be complex, so an easier way might be to take your total bill and divide it by the number of kilowatt hours to get the charge per kilowatt.

You can do the same with natural gas, only divide it by the number of ccfs which is usually what is found on a residential bill.

In the end you will find that heating anything with electric will cost more than with gas. One of the main reasons is you dont lose any energy in the pipe lines like you do in the power lines. Today a lot of electric is produced using natural gas turbines. Go figure.


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## M1Garand (Apr 12, 2006)

Thanks SS...I was looking at some and saw the electrics claimed to be more effiecient then I saw some of the tankless ones...but I'm not sure on them myself as I have well water and there's a fair amount of iron in it, even with a water softner.


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## stevevdw (Nov 7, 2007)

Splitshot said:


> If your company is telling people they can reduce their gas bill 30% by installing a tankless water heater I would call that deceptive, kind of like window salespeople telling you that you can save up to 50% of your heating cost by installing new windows.
> 
> We will never make any kind of claim like this. My 30% figure is based on actual customer's experience from their actual gas usage before/after the install. I know the Manuf. literature is littered with useless & deceptive info as well as anyone in the plumbing business. Splitshot sounds like a Pro & is right on with his advice not to believe everything you hear.
> The fact remains that as much as many contractors do not like the concept of the tankless heater it is here to stay. The rest of the world uses these things & sales figures in the States are growing every year. This despite the best efforts of the tank manufacturers who are all located in the US. Every DIY show is featuring these things & people are asking about them at every trade show. Take a look at ebay under any of the trade names & see how many you find listed. People are buying these b/c they are convinced these units will be cheaper to run & last longer. Initial cost is a factor but not the whole story.
> It always amazes me people will buy the highest eff. furnace they can find but will throw in a 80% eff. cheapo can water heater. The furnace they use 4 mos. out of the year & the water heater runs every day. If the plumbing industry became as focused on efficiency as the HVAC guys I think the tank-style heater would become an endangered species. Time will tell.


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## wagoneer (Nov 22, 2004)

We just had one intalled in a new cabin going up. The brand name is Rinnai. We haven't used it a lot yet since we are still building and it is a new place, so there is no comparison I can give regarding effeciency to a tank. Being new to this style, I did mess with it to see how well it works. The water temp seemed fine, even at low flow rates. The output temp is adjustable just like most tank style so you can protect from it being too hot.

I mostly did the tankless for the convience of draining in the winter, faster use when I get to the cabin, and the intended use (we may have 12 people at the cabin wanting a shower or it may just be me).

There are tax breaks available if this is going into your primary residence. You can find the forms and everything pretty easy online.


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## Splitshot (Nov 30, 2000)

Steve,

You are correct that tank-less water heaters are here to stay. I was only pointing out that they do not save much if anything except in some specific situations like the one Wagoneer wrote about.

One shouldnt just believe what the manufactures say, tax benefits withstanding


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## Shoes (Apr 12, 2000)

Okaaaaaay!! You've all given me lots to consider. Some very informative discussions with lots of pertinent information. Obviously I need to do some research relative to my situation. Thanks to all for your input.


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## jim sasser (Feb 19, 2007)

we just finished remod. our wash room and put this one in u can run 1-shower or 2-sinks.with just me and the wife its perfect,lots of water,no up/down pressure,real easy to install[u got to watch some of the bigger mod. the vent kit is crazy priced]this one use 5" double wall type b vent wich u can get at the hardwear store,1/2" water line,3/4" gas line.waiting for a couple of bills to see the diff. in gas usage...would recomend this one to smaller familes...A++


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## garybail (Aug 23, 2004)

I have been reading about these for 2 months looking to replace a 40 gallon gas water heater 
1/2 inch inlet-- outlet will reduce flow rate 
unit in basement pushing water to 2nd floor will affect everything 
flow rate, temp rise, fluctuations in temp, overheating, unit turns off then on then off again, gallons per munite, ect 
in northern climates temp rise must be higher due to colder temp water coming in
for the averaga 2/3 bedroom house spend about 800 
stay away from CHEAP china junk
follow consumers reports and you won't be sorry
you get what you pay for !!!
gb


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