Bosch AquaStar 125B NG Natural Gas Tankless Water Heater

Bosch AquaStar 125B NG Natural Gas Tankless Water Heater

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Aquastar 125 BNG

Aug 11, 2005
Review by  
Rated a Very Helpful Review

Pros:Constant hot water if you like to be scalded.

Cons:Demands consistent cold supply water

The Bottom Line: Do not buy.


At first we thought "what a great idea... saving money and energy", but the cons out weight the pros of this unit. We bought the Bosch Aquastar 125BNG tankless water heater from Home Depot to replace our still running 21 year old 40 gallon water heater. We went with a completely "non-electrical" water heater due to the fact that we live in Southern California and are subject to blackouts. (It's nice to know we can still take a hot shower with no electricity). The idea sounded great at first based on the limited sales information. Unfortunately there was not a lot of install history in our area that I could get references from.

We had the unit installed by the manufacturer's recommended plumber in our area and, before even purchasing the unit, had the plumber verify that we had the correct gas and water supply pressures to support this water heater. We were assured that everything was fine.

In our location the water heater is supplied with city water. When we first starting using the Aquastar it was December so the supply water was cold. All was normal until the seasons changed. The Aquastar warms up water just fine as long as the incoming water is a constant cold temperature. But when the supply water started warming up we could not reduce the control on the water heater low enough to prevent the heater from shutting off while still maintaining a comfortable temperature. Supplied with the water heater, after we have received the unit, the instructions tell us that it is best to adjust the heater control so that you add the minimum amount of cold water necessary. This, I feel, is vital information that we should have known before the purchase. Unfortunately, the minimum setting is too hot for my wife and kids. All this we find out after the heater is installed for a couple months.

Controlled Energy, the North American distributor provided a bulletin with suggestions on how to lower the temperature of the water without shutting off the water heater. None of the suggestions worked. I spent a couple of hours one evening adjusting the temperature control valve while monitoring the water temperature as I introduced cold water to the faucet to try and get a constant warm water setting. I found that I could raise the temperature control valve to maximum and introduce enough cold water to achieve a luke warm result but if I shut off the cold water, the hot water produced scalding hot temperatures. Imagine if one of my kids (or yours) were to accidentally turn on the hot water like this. I reverted back to a lower setting for safety.

My wife has been struggling with taking a shower that is either too hot or the hot water completely shuts off for the last 6 months. It puts a strain in the relationship. I have to constantly monitor the temperature of my kids bath tub fill to make sure it is not unsafe (too hot or too cold).

I called Home Depot to try and return the unit but I was fighting the water heater condition for 8 months and they would only take it back within 90 days of purchase. Again, I called Controlled Energy and ask if I could return it for a refund citing the "safety" issues and poorly detailed sales documentation. They would not honor my request.

So I will be reverting back to a tank water heater and eat the $479.00 cost of this tankless water heater. (Anybody want to buy a used tankless water heater?) My advice... talk to someone who has one of these installed before you make the investment. Also make sure the person you get references from is in your local area. The ultimate temperature that this unit reaches is greatly affected by the temperature of the supply water. Don't necessarily trust the advice from the recommended installation plumber. Try and find an independent plumber for advice. Bottom line... go with the Tank system. In the few months that we have had the unit we have not seen any reduction in gas consumption. In fact we have seen an increase. One friend mentioned that he thought the unit uses an awful lot of gas when it is heating the water. Perhaps more than a standard water heater uses to maintain tank temperature.

I am so discouraged by this technology that I will probably approach a consumer advocate group with regards to the safety of this type of device. At least this model.


Recommend this product? No

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