AquaStar Tankless On Demand Water Heaters

April 21, 2007 Update Addendum
I originally installed my Bosch Aquastar 125X tankless water heater in early 1999. In those years (1980s - early 2000) a company called Controlled Energy Corporation (http://www.cechot.com) was the USA distributor for Bosch Aquastar tankless water heaters. At some point in the past few years CEC HOT must have been bought out by Bosch and now Aquastar tankless water heaters are distributed directly by Bosch in the USA. The below page was first posted in 2001 and has several (now inoperative) links to CEC HOT's website which has since ceased operation. Web information on Bosch Aquastar tankless heaters can be now found at http://www.boschhotwater.com. As of 2007 they have introduced a replacement for their 125HX model called the 1600H (still utilizes their fabulous battery-less piezo electric hydro start pilotless ignition with a maxium 117,000 BTU rating). I would recomend staying away from their 1600P as no gas appliance should ever have a standing pilot light (unnecessary waste of natural gas). The 1600H still has a lower 0.6 GPM (Gallons Per Minute) turn on (Bosch's initial posted specs had originally noted the same 0.5 GPM as their previous 125HX, they must have just revised this specification). Bosch has a higher output (175,000 BTU) 2400 model but due to the higher 0.8 GPM turn on requirement I would recommend going with Noritz as their turn on is a low 0.5 GPM. Takagi used to have a higher 0.75 GPM turn on for their TK-1 and TK-2 units but recently they've released a TK-3 that has a lower 0.5 GPM. Unfortunately Takagi doesn't appear to list the turn on rate anywhere unless you call.

If I were to install another tankless (and I'd never consider a tanker water heater from its energy waste perspective = more CO2 global warming emissions, higher lifetime operational cost, far shorter life requiring replacement every decade) I would choose from the following tankless heaters in this order. The beauty of the Bosch Aquastar 1600H is its simplicity (no computer, least cost, no battery, no120 VAC power required). A friend just upgraded to the Bosch Aquastar 1600H tankless water heater and found it for $598.99 at Lowes. If you need more flow rate (realize most shower heads by law are restriced to 2.5 GPM flow rate) look at the Noritz units. With any of these heaters you will need to have adequate natural gas supply (3/4" gas pipe feed ideally from a larger main house 1.25" gas pipe). All of them will require some sort of flue upgrade either to 4" or 5". The Bosch Aqustar 1600H isn't a forced vent model and passively vents via a 5" galvanized steel flue (my preference is to install a dual walled flue for the entire run). The other units are forced vent (via 120VAC blower) and most likely require a dual wall stainless 4" vent. I know of several friends that opted to go Noritz in the past few years and have been very happy.

Bosch Aquastar 1600H (117,000 BTU, up to 4.3 GPM flow rate, and 0.6 GPM turn on)
Noritz 2007 Tankless Heater line. Main Noritz website is located here. While their N-063S (MSRP $999) would be totally adequate (180,000 BTU, up to 7.1 GPM flow rate, and 0.5 GPM turn on), I might splurge for the N-0751M (MSRP $1249) only because it comes with a digital remote control and if going with a computerized tankless heater why not get the cool display. The N-0751M has a more than adequate 199,000 BTU, up to 9.8 GPM flow rate, and 0.5 GPM turn on.
Takagi TK-3 (199,000 BTU, up to 7.0 GPM flow rate, and 0.5 GPM turn on). This particular unit has an air intake like the direct vent Noritz units (example: N-0751M-DV). Takagi has other units that aren't direct vent but without a listing of their turn on flow rate which in the past was always 0.75 GPM it feels easier to choose Noritz at least until Takagi updates their web information.

Lastly, you may have noticed Home Depot now carrying Paloma tankless water heaters. They have a $699 (118,000 BTU) and $999 (199,000 BTU) models with 0.6 GPM turn on. It appears Rheem carries these same heaters but rebadged with the Rheem brand name. Paloma's product selector page is located here.

To help slow global warming (reduce CO2 emissions), reduce energy consumption, save on operational energy costs, eliminate landfill waste (from tanker heater disposal every 10 years), and NEVER run out of hot water, everyone should be upgrading to tankless water heaters if at all possible. Europe mainly utilitzes tankless water heaters for the past century having always been concerned about conserving (costly) energy.

The majority of homes in the United States utilize a 40-50 gallon tank natural gas water heater to heat water for showers, kitchen, and laundry purposes. These tank style water heaters have a big environmental impact by consuming more energy, losing efficiency over time (increasing gas usage by 30% over 8-10 years), and inevitably end up in landfills. Tank heaters generally last only about 10 years. Some of the cheaper tank water heaters ($140 Home Depot specials) may only last 6 years before needing replacement. It is estimated that over 7 million tank style heaters are disposed of in landfills yearly.

Disadvantages of Tank Style Water Heaters used in residential homes:

Continuously keep ~50gallons of water hot at all times regardless of frequency of use. The natural gas burners ignite periodically to keep the 50 gallons at a preset hot temperature. This wastes energy.
You cannot use hot water continuously without "running out" of hot water. A tank water heater cannot heat water as fast as it is used by the nature of its design. I'm sure everyone is familiar with taking showers in lukewarm or cold water after previous family members "used up" all the hot water ahead of time with their showers. This can be a big inconvenience.
Soon after installation, sediment begins to build up at the bottom of the tank style water heaters. This sediment gets "baked" into the bottom of the tank and can seriously reduce the heating efficiency of your tank's burners. It is recommended that at least once a year you "flush" your tank style water heater by connecting up a garden hose and allowing the loose sediment to flow out of the bottom of your tank. Unfortunately though this can't remove the sediment that has already been "baked in" solid to the bottom of the tank. Also, few homeowners regularly perform any sort of maintenance on their water heaters.
There are corrosion issues with storing a tank full of water. Tank water heater systems use various types of sacrificial anodes made out of either aluminum, zinc, or magnesium. The material from these anodes end up in the shower, kitchen, or laundry water. They need replacement every few years yet few people regularly change out their anodes. Once the anode has been consumed the tank itself corrodes. Not regularly inspecting and changing tank anodes is a big reason why tank water heaters are replaced every 10 years or earlier.
If you turn down the heat on your tank water heater, you can promote growth of bacteria or molds which thrive in warm water environments. Keeping your tank temperature high generally keeps anything from growing (too hot) but consumes lots of extra energy.
Most natural gas tank water heaters have a standing pilot light. I have read that keeping the standing pilot light lit can consume $30 + of natural gas per year.
The tank water heater is generally very ugly and consumes lots of space in the garage where they are normally installed.
A tank water heater must be strapped well to the house's frame in case of earthquakes. A 50gallon tank of water will weigh on the order of 400lbs which could be dangerous if it were to get launched during an earthquake, not to mention it would rip itself from the water pipes.
Tank water heaters may also habor dangerous bacteria.

Advantages of Tankless On Demand Water Heaters like the AquaStar 125X

Hot water is available continuously for an indefinite amount of time. You can take showers for as long as you would like and the water is maintained at a consistently hot temperature. Never again will you hear the complaints from fellow family members that "You used up all the hot water!"
Water is ONLY heated whenever a hot water faucet is opened. An ingenius flowmeter within the AquaStar heater instantaneously fires off the natural gas burners and consisently keeps water hot for as long as the hot water faucet is left open. As soon as the faucet is turned off the natural gas burners shut off. You only consume as much natural gas as you need to heat the water you use. At all other times when no hot water is being consumed, the AquaStar consumes ZERO natural gas. This greatly reduces the amount of natural gas consumed lowering the monthly gas bill.
The AquaStar 125X model has an electronic ignition system which completely eliminates any wasted natural gas due to standing pilot lights. If you never turn on any hot water (say while on vacation), you consume no natural gas. Any gas that you are not using helps reduce your monthly gas bill.
The AquaStar tankless water heater weighs only about 30lbs. It mounts easily and cleanly to a wall freeing up lots of floor space in a garage.
The AquaStar tankless water heater has no corrosion issues since it has no tank and no need for sacrifical anode rods. The entire Bosch made copper heat exchanger ensures corrosion and sediment free operation.
The AquaStar is fully rebuildable. The heat exchanger has a 10 year warranty but most likely will last much longer. If/when it would require replacement, instead of disposing of a massive tank water heater...you just replace or repair the components of the AquaStar that require attention. This reduces landfill pollution and is much simpler than having to remove and reinstall a bulky and heavy tank water heater.
The AquaStar incorporates extremely high quality construction and materials. This fact will insure many trouble free years of operation.
The AquaStar is beautiful. It brings smiles just looking at its efficient, compact and clean design hanging on a wall. Even after 2 years of operation my AquaStar looks as new as the day it was installed. There is not a single sign of corrosion around any of the copper or brass plumbing.
You can carry the AquaStar Heater out of your local Plumbing store under your arm. You don't need a truck or forklift to move this tankless water heater like you do with bulky and unwieldy tank style heaters.
The AquaStar design guarantees you will save $$$ on your natural gas bill.

Stefano's AquaStar 125X Experience

I installed an AquaStar 125X electronic ignition tankless water heater at the beginning of 1999. It replaced a 12 year old failing 50 gallon tank style water heater which had serious sediment buildup and massive corrosion on the inlet/outlet water pipes because it had been poorly maintained by the previous owners (no sediment flushes or replacement of anode rods).

I lived with the failing tank water heater for a year before replacing it with the AquaStar 125X heater which was first released for sale in January 1999. I nursed the tank heater along so that I could swap it out with the AquaStar 125X once released. I performed numerous sediment flushes which revealed an amazing amount of gunk buildup in the bottom of the tank heater. A leak due to corrosion of the water inlet/outlet pipes had to be dealt with. The burner assembly also required a replacement thermocouple.

During the year I lived with the tank water heater my natural gas bill revealed I regularly consumed 13-15 therms (a therm is a standard unit of energy) of natural gas per month. Natural gas powers my stove, laundry drier, furnace, and water heater. I don't use the drier more than a couple times per month and rarely turn on the furnace. My main usage for natural gas is to heat water for my daily morning 5min shower.

1 therm = 100,000 British thermal units (Btu)

In 1998 1 therm of natural gas cost about $0.50 per therm for an end customer. At 15 therms per month the portion of my bill for the natural gas amounted to $7.50 not counting the daily service customer charge of $0.16 per day. Gas was cheap back in 1998.

As soon as I installed my AquaStar 125X tankless water heater my therm usage per month decreased to a miniscule 2-4 therms per month. At $0.50 per therm, 4 therms represent $2.00 of natural gas usage per month! My daily customer service charge of $0.16 per day actually is the majority of my bill at around $5 per month (31 days). By swapping out my tank water heater for a tankless water heater I was now realizing $5.50 savings per month or about $66 per year in natural gas savings. This is fairly significant in my mind. This proves that keeping 50 gallons of water hot continuously with a tank style water heater uses about 12 therms of natural gas that is just wasted continuously month after month after month. One could argue that in 1998 natural gas was cheap but that doesn't mean we should waste our natural resources.

Fast forward 2 years to January 2001. I'm still using between 2-4 therms per month and my AquaStar 125X water heater is performing at peak efficiency (no degradation of performance due to non-existent sediment buildup). In the last few months there has been a countrywide shortage in natural gas reserves. The cost of natural gas has been rising to $0.80 per therm and the last bill showed $0.90 per therm. The rise in cost of natural gas has not only impacted home and water heating, it has caused an increase in electricity since a large percentage of electrical generation is done with natural gas burning turbines.

If I were to still have the inefficient 50 gallon tank water heater, 15 therms would equate to $13.50 per month (keeping 50 gallons hot all the time). With the AquaStar at 4 therms per month my cost is $3.60 per month. That represents a savings of $9.90 per month or $118.8 per year! If natural gas prices continue to increase I will only be saving more and more $$ each month.

I'm thoroughly impressed with my AquaStar 125X water heater. I get consistently hot water for as long as I desire (no "running out" of hot water). I really like how energy efficient it is with regards to minimizing the amount of natural gas I consume and in the process keeping my natural gas bill to a minimum. It still takes about the same amount of time (a minute) to get hot water at the furthest shower head from the water heater as one must still rid the "slug of cold water" from the hot water pipe leading to the shower. The only way to reduce this would be to have really short pipe runs between the water heater and the shower but houses are not designed with this desire in mind (yet) which would help save water. There is a high volume electric water pump recirculation system called the D'MAND System that will eliminate any water waste waiting for hot water to arrive at faucets located far away from the water heater.

Installing an AquaStar 125X tankless water heater is a win-win situation on all fronts. It minimizes natural gas usage and saves money. It provides consistently hot water indefinitely when in use. It is fully rebuildable (no disposing of massive tanks in the landfill every 10 years). It has no corrosion issues since it has no tank and no need for a sacrifical anode. It frees up space, is earthquake safe, and is a gorgeous appliance providing pride of ownership. You just can't get excited installing a run of the mill wasteful tank style water heater. Install an AquaStar and you'll smile everytime you walk by it.

Funny Story Involving the Gas Company

Immediately after I installed my AquaStar 125X water heater my gas usage plummeted from ~15 therms per month to 2 therms the following month. When I received my gas bill for the first month after installing the AquaStar it was for 102 therms. The gas meter reader guy had figured there was no way I just used 2 therms over an entire month and misinterpreted the meter to read 102 therms.

I called the gas company and spoke with a represenative in customer service noting that my bill was 100 therms overbilled. The representative then began asking me all sorts of questions including "How many gallons does your water heater tank hold." I responded "NONE! ZERO GALLONS! I have a TANKLESS water heater". This didn't register with the gas representative and she again asked me the same question regarding how many gallon tank is my water heater. Finally after 5 minutes of explaining that I had just changed my water heater to a new super efficient tankless water heater did she finally start understanding. She still could NOT believe that I would only use 2 therms for an entire month of hot water usage and was going to send someone out to do an inspection. This was the first she had ever heard of a water heater being "tankless" let alone using so little gas.

It seems that other people have had similar experiences. Here is a letter archived on Controlled Energy's Website from a power utility to a customer who just installed a Tankless Water Heater.

Purchasing an AquaStar Tankless Water Heater

AquaStar tankless water heaters are available in several models depending on your application. The ideal Aquastar model for use in a typical non solar US residential home is the 125X which incorporates electronic ignition eliminating any standing pilot light. The 125X retails for $799.99 but I purchased mine at a local plumbing store for $695. A friend just ordered an AquaStar 125X online for $576 which came to just over $600 with shipping. In any case an AquaStar 125X is only $100-200 more than a high quality electronic ignition 50 gallon tank water heater. The little additional cost is instantly recouped through the monthly savings in gas usage especially with today's increasing natural gas prices.

AquaStar has made a 125B model for years. It retails for $699.99 and has a standing pilot light. The 125B sells for $475 at the local plumbing store. It is false economy though to purchase any appliance that wastes natural gas continually through a standing pilot light. Demand that your water heater have an electronic ignition.

The 125X model uses two D-Cell alkaline batteries that provide the electrical energy to ignite the burners. These batteries should last 2-4 years depending on usage. I've already had 2 years of usage from the original D-Cells I installed in my 125X and they are still going strong. There is a red LED on the 125X front panel that will start to flash 2-4 months in advance of the batteries being completely discharged. This feature gives ample warning to allow you to replace the D-Cell batteries.

Installing an AquaStar Tankless Water Heater

You can read about installation requirements on Controlled Energy's website. Because a tankless heater heats water on demand in realtime, it uses significantly more gas while in use than a tank style heater's burners. You save energy based on the fact that you only burn gas while hot water is use. You are not keeping and re-heating 50 gallons of water continuously like is done with a tank style water heater. Because the AquaStar uses more gas while its burners are lit, you need a larger diameter flue (minimum 5" diameter is recommended). The supply gas line also has various requirements (minimum of 1/2" diameter if 10ft or less, otherwise 3/4" diameter is recommended as per Controlled Energy's website).

The typical tank water heater installation has a 3" diameter flue. Mine was 3" and I had to upgrade it to 5" to meet requirements set forth in the AquaStar installation specifications. The Controlled Energy Website should be able to answer any and all questions regarding installation requirements of this marvelous AquaStar tankless water heater.

12 year old corroding and failing 50 gallon Tank Style Natural Gas Water Heater with standing pilot light. Ugly and wasteful!	Note 3" flue and ugly earthquake safety restraint straps.	Tank be gone!
Original wimpy 3" rooftop flue.	Installing the upgraded 5" flue rooftop flashing.	New upgraded 5" rooftop flue.
AquaStar 125X installed and functional.	The 2 cross "boards" are pieces of 5/8" drywall to provide proper spacing in anticipation of drywall installation.	AquaStar 125X with 5" flue. Water inlet and outlet lines had to be shortened and now enter the water heater from below instead of on top like tank systems.
Closeup of the piping. Brass fittings were used to allow easy construction of the valving network.	The AquaStar 125X in final mounting configuration with new drywall, texture, and bright white paint.	Gorgeous! These "drywall" completed pictures were taken 2 years after initial installation! No corrosion and the heater looks brand new.
Closeup of the piping. Cold water enters on the right and can be closed off with a globe valve. Natural gas line feed is in the center. Hot water exits on the left where a temperature & pressure relief (TPR) valve is located. A globe valve allows closing off of hot water to the house. A t-fitting with another globe valve and leak proof quick disconnect coupler allows a garden hose to be hooked up to drain the heat exchanger for future service. It could also be used to provide hot water to wash a pet.	Corner view.	Looking upwards at the 5" flue ceiling pass through. The knob located at the bottom of the picture allows temperature adjustment of the AquaStar's burners. The flip down panel just to the right of the knob houses the single on/off switch and LED battery level indicator for the electronic ignition system of the 125X model.
AquaStar 125X and flue combo picture.	Beautiful!

This is my aunt's 20 year old tankless water heater!	This unit heats sink, shower, and laundry water. It also heats water that is part of a circulating closed loop radiative house heating system.	Front panel controls.
Service manual and installation/operation manual.	Another tankless water heater in Bologna.	This heater which services an entire apartment is mounted in the kitchen by the stove concealed behind a cabinet door.
Yet another tankless water heater also intalled in the kitchen.	This is a powered vent bathroom mounted tankless water heater.	Closeup of this heater's particular controls.