# Let' Discuss Tankless W/H'rs..



## 12vman (Feb 17, 2004)

I guess I can't figure the savings when one is used in a full time scenario. I understand if one was used part time in a weekend cottage but how can it be justified for everyday usage?

The flame is huge while in use and cautions about the chimney are everywhere. They must use a lot of fuel to keep the temperature up of flowing water.. Everytime the spigot is turned on..

Thinking of a standard H/W tank, The burner is no way as big as one used in a tankless unit. I figure the energy used in just one shower with a tankless unit could possibly heat at least two or maybe three 30 gal. tanks. That's a bunch more than what's used in just one shower. The only incentive I understand is the fact of continuous hot water..

Even during the night if a standard tank was to kick on to maintain the temperature a couple of times, I don't believe it would use as much fuel as a tankless unit during say.. One load of clothes in the washer or a nice hot bathtub full of water..

I don't own a tankless unit and I don't know of anyone close to me that does. Are there any folks here that have one installed, Using it full time, That can 'splain this to me? 

I heat all of my water with a standard 30 gal. tank using only the pilot flame. This supplies me and the little lady with a nice, hot shower, Sometimes twice a day. It recovers nicely over night without the need to blend in any cold water at the shower. If I expend the tank, (Which is rare) The recovery time can take a couple of days but it does come back. If I need hotter water for dishes or what not, I just heat a pot full on the stove to make up the difference. I wash my clothes in cold water, BTW..
~Don


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## SolarGary (Sep 8, 2005)

Hi 12V,

I've never heard of the pilot only scheme -- thats pretty neat.

I don't see how it would pay you to use a tankless.

If you use a "typical" amount of hot water, the energy factor thats shown on the energy tag for the water heater is supposed to indicate how efficient the water heater is for typical use.
The tankless ones are around 0.85 and the tank type (I think) around still around 0.65. I think this is due mostly to the high standby losses from the big flue that runs up the middle of the heater that vents the combustion products (and some of your tank heat) to outside.

If you only use the pilot, I wonder if you need to vent to outside at all?
Any idea how many gallons of hot water you can make in a week with just the pilot?

Gary


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## oreo (Jan 14, 2007)

I don't understand fully how it all works but my propane usage has gone down quite a bit. I am only paying to heat water when I want it. My Rinnai uses electric ignition so I'm not even running a pilot. Their website has a savings calculator and some info on how it works. I will be getting a $300.00 tax break, too! My unit is on the outside of the house so no need to vent (extra piping in walls ,etc.). The flame to heat the water is also based on what temp I set it to. I can run multiple showers with no drop in water temp. I figured it will pay for itself in about three years, and then I will have about a 30% savings annually. I replaced an older propane tank heater. HTH


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## Tango (Aug 19, 2002)

I've an Aquastar pilotless. It is a single application heater but many times I've washes dishes when someone is in the shower and don't hear a scream so I think two applications are handled very well. Because the pilot comes on only when someone turns on the hot water, it is a cost savings in terms of propane for me. A couple of things I don't like are that it is subject to freezing (the one Bosch makes for outdoors is a pilot light all the time model), and sometimes when my water pressure drops the water runs cold and it takes a long time for hot water to reach my upstairs shower again (!!!) It needs a steady water pressure above 26 psi. In a more conventional house where the water system was a bit more developed than it is at my house, I think a tankless, pilotless water heater is the way to go.

BTW, I spent a lot of time with my grandparents who always turned off the water heater and there never seemed to be enough hot water. It was a drag. Hot water for a shower is one of my few conveniences - I love a scalding shower every once in a while, though I don't have all the kinks worked out of the system. In terms of my lifestyle, the tankless, pilotless makes a lot of sense- it might not for you. Sounds like your system is down very well


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## Andy Nonymous (Aug 20, 2005)

Yes, I've known of gas fired water heaters that will provide good warm water on the pilot alone, and with propane, properly adjusted, the level of CO released is low enough to possibly not need a vent in typical construction homes (the super efficient 'air-tight' home *will* need it, for any combustion process). Natural gas does not burn as clean, and should not be un-vented. Some people are affected by even cooking with natural gas ranges, which would be a higher combustion rate than a water heater pilot by far, but for a much shorter period of time. Over the course of a day? the pilot may be the worse offender. Just because something can be done, doesn't necessarily make it a "good idea". Caveat emptor.

I have installed tankless heaters, and used the water from them, but never owned one personally, and currently only heat water as needed, ether by wood cookstove (that does other cooking duty while heating water), or by small propane stove. Yes, tankless heaters are not quite as efficient in Â°rise / gallon / btu input as evidenced by the significantly higher stack temperatures than a 'standard' (not "fast recovery") water heater, but more than make up for it in no loss when in 'standby', which is what most water heaters do most of the day. 

Just for examples, a 'standard' water heater burner uses roughly 25-35K btu per hour, with the fast recovery units going as high as 60K btu, in both cases depending on tank size - the larger the tank, the higher the burner input. Tankless heaters run roughly 100K btu or more. As a point of reference, my propane cook stove burners use about 5-8k btu each, on high.

My personal experience with tankless heaters is that water flow has to be very steady to maintain a given temperature, and for people with wells and water systems that 'surge', or numerous occupants in a house that may draw water at any given time, it can be tough to get an even (or even comfortable) shower temperature, though they supposedly have improved since my last experience. I'd love to hear of others current experiences with them on well systems.

YMMV, Andy


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## gregbaka (Apr 4, 2007)

I've been using a tankless H2O heater for 7 or 8 years now, the Aquastar 125B (B for battery ignition - no longer available). Even moved it with me from one house to another. I have also installed 2 newer Aquastars for friends.

The previous posters did a nice job of explaining why they truly do use less gas for normal families under normal use, so I won't restate that. But I can give some other insights on how they can save even more money AND lead to changes in your hot water use habits....

The biggest savings come in tandem with changing your hot water habits. Although there are decent savings for the "average" family that has "average" hot water use habits, just imagine how much bigger those savings are for a family that has very frugal hot water use habits. My family experience has been that using a tankless promotes very frugal hot water habits.

First, there is the very visible, very dramatic flame when the unit kicks on. My kids grew up seeing this flame - they now mentally connect turning the hot water faucet with that huge gas flame. And I have told them many many times that Energy=Money. So we developed the habit of not turning the hot water tap unless we REALLY wanted the hot water.

Second, there is the pause between turning on the hot water tap (the pause will vary by pipe length and diameter). This pause also reinforces the message of "Do not turn on the tap unless you REALLY want hot water." We also wrapped the hot water handles of the sink with bright red pipecleaners so that there was a visual and tactile reminder to not just flip on both handles every time you use the sink. As a result of this we have all developed the habit of using low flow of cold water for quick handwashing - especially after experiencing the fact that the hot water doesn't show up until you are done anyways.

With this awareness also came the acceptance that:
1) modern detergents do not need hot water - we do not use hot water for our washing machine
2) a dishwasher on Normal wash cycle is much more efficient than one set on PotScrubber - so scrape and rinse the dishes (in cold water) before putting them in the dishwasher and use the lighter settings.
3) a quick shower is for getting clean, while a long hot soak in the jacuzzi tub (or a long hot shower for my teen) is for luxury, for a special treat. The long hot showers and soaks do still happen, but they are acknowledged as treats. Regular body maintenance is short showers.
4) it will easily run more than one fixture at time, though running two heavy flows like the shower and dishwasher is best avoided unless you like invigorating temperature swings while showering

I would guess that our tankless heater only turns on 4 or 5 times a day. And that is where the big savings come in. Otherwise we would be keeping 30 or 40 gallons of water hot 24 hours a day for those few uses.

A few other Aquastar tankless water heater tips:
1) turn the temperature dial down in the summer and up in the winter - winter ground water is colder and needs the extra heat
2) take the flow restrictor out of your shower head - the heater needs a minimum flow to allow the burner to stay lit and most low flow restrictors fall below that level.
3) load your dishwasher, then wash the leftover pots and pans right before turning on the dishwasher so that the pipes are full of hot water for the dishwasher.
4) remove the heater cover and dust or vacuum the dust away every year or so to avoid toasted dust bunny smells.
5) if you think you might ever possibly get a solar water heater, buy the Aquastar 125S (S for solar) - it only costs about $50 more and will operate just like a normal tankless heater during the years you are saving up for your solar water heater. But you will then have your back-up or booster heater ready when the solar system is installed.

Greg in MO


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## 12vman (Feb 17, 2004)

Thanks everyone for your input. I've seen one in operation and it was hard for me to figure where the actual savings came in being the flame is so huge! I understood the fact they only use fuel when needed but the flame in a standard water heater is no where as big. I guess it's in the length of time the burner operates..

In my system, The pilot flame stays on 24/7 and the burner never kicks on. I restricted the flue to contain the heat from the pilot inside as long as possible but allowing enough flow to keep the pilot burning. I don't have the flue going outside. The pilot flame in the water heater is smaller than the flames in my fridges. My home is nowhere close to airtight so thats not an issue..

The input water is usually at room temperature being I store it in my living area in the utility room. In the summer months, The water gets so hot at times I can't get under it! In the winter, The utility room stays a little cooler than the rest of the house and the temperature doesn't get as high. If I installed a blanket on it, I figure it would work as well as it does in the summer..

I've never taken an actual temperature reading of the water but it will make steam and make you look like a lobster.. lol
~Don

To Edit: Quote from Gary..

"Any idea how many gallons of hot water you can make in a week with just the pilot?"

I figure with showers and doing dishes.. Maybe 60-100/week. I never run it 'till it gets cold. It just needs to reheat maybe 10-15 gal./day. (About half of the 30 gal. tank capacity) Some days a little more, Some days less..


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## Lisa in WA (Oct 11, 2004)

BackwoodsIdaho said:


> Trendy? No. Efficient? Yes
> 
> A 40 gallon hotwater (Whirlpool Flame Lock) tank uses 40K BTU/Hr assuming an efficiency rating in the range of 75% and a flow rate of 66 gallons per hour. A tankless water heater uses 235,000 BTU/hr assuming a an efficiency rating of 82% and a flow rate of 300 gallons per hour. This works out to 783 BTU's per gallon for the tankless water heater and 606 BTU's for the tank based heater. So, on first look, it appears that the tank water heater uses less btu's than a tankless. However, the tank based water heater has to keep the water hot all the time rather than just when it is being used. Let's assume a duty cycle of 5 mins every 2 hours for the tank based heater to keep the water hot, that works out to 5 mins X 24hours/2hrs x 1hr/60mins = 1 hr of heating per 24 hours to keep the water hot, so we add another 40,000 BTU's just to keep the water warm. Now, lets assume that the avg family uses 100 gallons of hot water daily. In that scenario, the family would use 60,600 BTUS for heating water plus 40,000BTUS to keep it hot for a tank water heater for a grand total of 100,600 BTUS daily. For a tankless water heater, it would be 100 gallons x 783 BTUS per gallon or 78300 BTUS per day with a tankless. So, in conclusion, the tankless would save this family 22,300 BTU's per day. Considering that propane has approximately 90,000 btus in a gallon, this equates to ~157 gallons of propane per year or (at an avg. cost of 1.60 per gallon) about $251. Which means that the tankless would pay for itself in ~3yrs. This analysis does not take into account the 10yr lifespan of a tank water heater vs the tankless and it does not take into account the cost of floor space for a tank water heater vs. hanging the tankless on a wall.
> 
> ...


....


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## 12vman (Feb 17, 2004)

Thank you, Lisa! That just about says it all..


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## strider3700 (Feb 2, 2007)

thanks lisa using those numbers the tankless used 75% of the energy that the tanked unit used. reducing the usage to 25 gallons/day (only two of us and we conserve) it uses 35% as much with the pilot light adding up to 73% of the energy used by the tank heater. 

This is all a mute point for me however as I currently have an electric water heater and need to conserve space in the tiny bathroom so the switch is more about space savings if I can make it work.


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## WayneR (Mar 26, 2007)

Might want to consider the hardness of your water supply. Have been told by several people that these heaters are prone to stopping up and must be taken apart and cleaned annually. Weak acid or vinegar solution. Have also been told that such cleaning must be done by a dealer or the warranty is voided.

These expenses may negate the benefits of lower energy costs.


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## Jim-mi (May 15, 2002)

Those are interesting figures.
But around here the hot water use is far below 100 gallons per day. . . . .even with a "long" shower.

Also most times I use the hot at a very low flow rate. From what I hear my common flow rate useage would not be enough to keep the tankless fired up. . . . . . . So why should I use alot more water . . . .just to keep it warm . . . . .I can't justify that reasoning.
Most of my 40 gal propane tank has at least an aditional 6" of fibreglass insulation around it . . . . .not just one of those skimpy blanket wraps . . . 
So I figure with all that insulation, it will retain that much more heat . . . .longer.

They work well . . . . . . but they are not for everyone.


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## gregbaka (Apr 4, 2007)

WayneR said:


> Might want to consider the hardness of your water supply. Have been told by several people that these heaters are prone to stopping up and must be taken apart and cleaned annually. Weak acid or vinegar solution. Have also been told that such cleaning must be done by a dealer or the warranty is voided.


This is not true for the modern home-scale tankless water heaters. 

There are COMMERCIAL tankless water heaters used for places like restaurants, laundries, etc that get the water VERY hot and those units have had problems with scaling. The intense heat accelerates the depositing of the minerals.

But home-scale tankless water heaters (at least the Aquastar units I have installed) have a temperature limiter that prevents them from getting so hot that the minerals deposit in the tubing. Like I said before, I have used the same Aquastar for 7 or 8 years now, in 2 different homes, with no maintenance problems at all. 

Greg in MO


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