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Tanklets > Tankless Water Heaters

Q: Hi everyone. I am considering installing a NG tankless water heater that meets CSA standards and has had some good reviews. I am considering a "whole house" system and was leaning towards the Bosch E2400, however it does not receive many good reviews. Since then, Home Depot has started promoting the Rheem EcoSense Tankless Water Heater ECO-180 DVN3 that specs out very well, but I can't seem to find any reviews on it.

I am wondering if anyone has any experience with this unit and woiuld like to share their thoughts. Also, Home Depot does not sell the installation kit for this unit, so I am woindering where I might find that as well. Any thoughts / comments would be greatly appreciated.

A: I can only relay our family's experiences with a different brand of tankless water heater than you are considering. We are now replacing a unit that was installed in Nov 2006. Yes, that is after only 3 years and 9 months with a 3 year warranty on parts and 1 year warranty on labor.

The system we have (are replacing) was a Stiebel Eltron Tempra 24 Electric (T-24). House is 2100 sq ft having 2 bathrooms and 4 persons. Many of this website's "Tankless, Its Limitations, and Interesting Alternatives" article's points are sound and the advice good. I would say that we did experience some overall utility cost savings but this was compared to a contractor grade gas water heater (with gas prices skyrocketing) and should be balanced against the much more expensive cost and installation of a whole house tankless water heater.

Lastly, the warranty on parts is considerably less that traditional water heaters and I'd go further to state that the complexity of design of these systems creates more opportunities for things to fail than traditional water heaters. All our opinions based on our actual experiences. -- FamilyJax

A1: I would not suggest any gas tankless water heaters as a replacement option. There are many verying opinions. Here is what I see as the problem with your replacement installation. "Cold Water Sandwiching" is a big problem with any of these units. Google this issue and you will find countless complaints and associated manufactures rhetoric.

These units are really a balance of physics. Your domestic hot water piping existing in your home can also work against this type of installation. Owners have experienced issues with not being able to serve more than one fixture at a time. I have seen where the dishwasher will starve the shower when running at the same time.

There are several points you should consider.

* Inherent to heating cold water is lime scale WILL develop no matter what type system you choose.

* Tankless units have to be regularly cleaned of the lime scale. Much more often than tank type heaters.

* BTU inputs are the key behind your GPM of these tankless heaters. If you live in a cold weather environment The BTU's will determine the real size of the units. Many manufactures of tankless talk about GPM. Pay particular attention to the temperature rise and the literatures entering cold water specification.

* Bosch, Rheem, AO Smith, State, GE traditionally do not manufacture these units. They are private labeled from companies. The main manufactures are Rinnai, Noritz, Tagai are a few of the big boys in the manufacturing. They are Asian companies.

* Recommendation: I would look to the AO Smith Vertex heater as an option. The GDHE50 has a 100,000 BTU input. This unit has 96% Thermal efficiency based on ANSI Z21.10.3. This is outstanding. It is vented using PVC pipe which is very inexpensive. This unit Typically runs around $2000.00. The pay back is awesome. Highly recommend. -- HotH20Lover (8/28/10)

Q: I am considering replacing my conventional tank-style water heater with a tankless heater, but I also have a circulating heat loop in the existing system that keeps hot water available at every discharge point. Will such a heat loop work with a tankless system? Do tankless systems respond to pressure drop or temperature, or both?

A: Hello: Some people suggest putting a small tank heater downstream of the tankless and running a recirc loop to the little tank. I suppose you could do this with demand controls, but certainly not with with the usual controls or you risk a much higher electric bill. There are different tankless controls, but both pressure and temperature can be used. My question is what is the reason you're considering the switch to tankless?-- Larry

Q1: I am trying to save fuel cost. I am on propane.

A1: One problem is that tankless heaters cost several times more than tank-type heaters. A key issue for you is that recirc line. That radiates away heat all the time it's on. Rather than switching water heaters, you might think about switching from a recirc to a Metlund D'Mans system that only delivers hot water when you press a button. -- Randy

Q2: Randy, Never heard of Metland DMand system. Checked it out and it looks like a good fit. Thanks! (8/19/10)