Tankless water heater

[Rick Maday]

Looking for opinoins about tankless water heaters/insta-hot vs. conventional water heater. Installation issues, cost to operate, maintenance, safety, etc.

Thanks for your help.
Rick

[Bruce King]

Lots of info on the web about those,

Many people find out that they have to upgrade the size of the gas piping when replacing a regular gas water heater with a gas tankless unit.

Same thing with electric, a good tankless one will draw more amps than the typical water heater circuit.

[Jeff Spencer]

Rick,

I'm in the process of evaluating tankless water heaters for my own house.

There are significant cost differences between installation in a new build or retrofit in an older house.

The cost of the water heater (I'm narrowed down to gas), assuming a whole-house unit, is between $850.00 to $1200.00. Several important considerations are:

1. depending on the size of the unit, you need electrical service equipment that can accomodate from 2 to 6 double-pole breakers to handle the water heater's staging. In older houses, this may require ugrade or replacement of the panel and wiring -- a potentially expensive proposition given current copper prices. It may also require an upgrade in system ampacity.

2. gas units may require renovation of gas distribution plumbing. In my house, I would have had to replace over 60 feet of 3/4 gas pipe to 1.5 inch if I wanted the water heater installed in the laundry room where the conventional unit is now. Cost was about $1,500.00. Fortunately, I can mount an exterior unit about 6 feet from my gas meter for less than half that amount.

3. If a gas water heater is installed in the attic or within the house, a stainless steel flue and cap is required. This costs from $400.00 to $500.00 additional.

4. If you're not putting either tankless unit in the same place as the existing unit, you will have to re-route or tap into supply plumbing. Depending on the location, you may need to break into walls, necessitating additional cost for sheetrock work.

Having inspected a number of electric and gas units and talking with homeowners, most have noticed a rather significant impact on their utility bills after installation. Heating cycles of tankless systems are generally shorter, and you don't pay for storage heating. Calculations on the heater I'm looking at put me at somewhere between 17 and 20 percent cost savings over my current conventional water heater.

Jeff

[Michael Thomas]

I have gas fired tankless water heaters at my home, my office and at 3 of our rentals. They can work well, but we encountered a number of issues when installing them.


I’ve put up this page describing some of the installation issues we encountered, and how to resolve them:


Tankless Water Heater Installation FAQ - Paragon Inspections Evanston / Chicago (http://www.paragoninspects.com/tankless-heater-home-inspection-evanston-chicago-il-faq.html)

[BARRY ADAIR]

Appears AO Smith would prefer consumers to purchase storage units...very few if any of the plumbers I know own tankless...

http://www.nyletherm.com/whitepaper2.pdf

Conclusion
Tankless water heaters have advantages. They are
compact and are easy to drain; consequently, they
could be ideal for applications where space is a
premium or in small vacation homes. In addition,
they could serve quite effectively in point of use
applications. However, their use as the central
source of hot water in a residence should be carefully
considered. While tankless water heaters offer
some modest energy cost savings over storage
water heaters, those minimal gains are at the
expense of higher initial costs, higher installation
costs, higher maintenance costs and the potential
need for lifestyle changes to accommodate the limited
flow rate output of tankless water heaters. In
addition, with the coming increase in Energy
Factor required by NECA II, the Energy Factor differences
between tankless and storage water
heaters will become even smaller.
If a customer regularly runs out of hot water
from his storage water heater, the most cost-effective
solution is the purchase of a larger, correctly
sized, high-efficiency storage water heater. For
those who want enhanced energy efficiency, the
most cost-effective solution is the purchase of a
correctly sized, high-efficiency storage water heater.

[Rick Maday]

Thanks to all.
Rick

[Will Decker]

Many plumbers, in my area, do not like or recommend tankless water heaters. I have found that is is because:

1) They have a distributorship with a non-tankless manufacturer.
2) They don't know how to install them (very important).
3) They think it is a new, fad technology.
4) They don't think they can sell them because of the higher initial cost.

To properly install a tankless, 3 criteria are needed:

1) Must be a qualified plumber.
2) Must be properly qualified in HVAC venting.
3) Must be factory trained and qualified by the manufacturer.

There are now full cat 4 units that do not require stainless steel vents (just PVC).

I also recommend that you purchase the stainless steel models, not the copper models. Much more long lived.

With a lifetime (guarenteed) of more than 4 times that of a conventional unit, not to mention the gas savings (for gas models), they are great.

Most problems revolve around inexperienced and/or unqualified installers. Definetely not a "pick it up at home depot and install it yourself" deal.

Hope this helps;

[JB Thompson]

I, too, have looked into replacing my current gas unit with a tankless version. I did find by talking to homeowners who currently own a tankless that the common consensus is: they prefer the old conventional water heaters.

Part of the problem is that many people like to kick up their heater beyond the 140 deg. limit (at least that is the limit for Rinnai). Most homeowners said the water didn't feel as hot as they were accustomed.

[Markus Keller]

You know who talks smack about tankless units? Plumbers who don't know how to install them.
It's not a new fad. They've been around for a long time.
Proper installation is key.
All the units cost pretty much the same. My suggestion is to concentrate more on install location and vent piping needs. The biggest cost difference is in the vent piping among the manufacturers. Rheem shoves it to you on vent piping and terminations. Bosch isn't too bad on those prices but very picky on the install. Consider the amount of run you will have.
I would recommend the Rinnai units. Easy install. Vent piping is cheaper and you can make longer runs. I haven't had any problems over time with any of the above mentioned units ... but the Rinnai is my favorite sofar.
- Supply piping run is key to satisfactory use. Some people equate 'tankless' with 'instant'. Don't make that mistake. If you can shorten the run, do it.

[Bob Harper]

Markus, I'm a little confused on the part about costs of vent piping. I looked up a Rinnai and it listed all the major brands of AL29-4C cat. IV venting. Can you explain?
TIA,
Bob

[Bruce King]

I just remembered an issue that many people will not like with tankless.


Large house (4k+), one water heater, flow is low on hot water due to the tankless water heater's normal operation therefore it takes forever to get hot water to most of the house.

I was told by the builder that the hot water flow rate is not adjustable.

It saves hot water at sinks because you never get any and give up trying.

[Markus Keller]

Bob, the Rheem and Bosch units sold around here all have/require stainless steel vent pipe. Some 2 pipe some concentric, which makes it a pricey install. The Rinnai vent piping sold here is an outer PVC type jacket that pulls in the combustion air and an inner either stainless or aluminum pipe that exhausts out the flue gases. We know it as a concentric pipe set-up. (Rheem used to sell them for their 90+ furnaces. Don't know if they still do or not, since none of the hvac guys bought it a second time, pain in the ass to use.)
Anyway, my guess is that because of the outer sleeve not being stainless the pricing is better.
I don't recommend people put only one tankless in a large house with multiple bathrooms etc. I recommend isolating floors or fixture areas and installing 2-3 units. I know this gets expensive but there are benefits.
Traditional house with normal fixture unit count one unit works well.