[SGVLUG] OT(TTM) Tankless Water Heater

[Emerson, Tom (*IC)]

-----Original Message----- Of DYN: Jim Workman

Off Topic (To The Max):
I need to replace my water heater and am considering a tankless model.  Is anyone already using this new technology?
Any feedback?
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I had one installed last winter - since this is now outside the house "near" the gas feed line, it is now on the "other side" of the house from where it was before.  Net result is that the taps that were close to the old location now take about a minute before the "hot" water gets there (OTOH, the bathroom just the other side of the wall from the new location gets hot water in about 5-10 seconds ;) )

Minor plus: this has freed up room inside the house for shelving / cleaning-supply storage  (although considering the actual size of these units, had I gone for an ELECTRIC heater instead of GAS, I could have installed it in the same location AND had room for vacuums, mops, and chemicals...)

Cost to run the gas line tends to be a hidden "gotcha" - if you're doing a major remodel or a new build, this would be the time to do it as the cost gets absorbed into the larger project.  Unlike a traditional heater, these need a much larger gas feed - usually 3/4" or 1", compared to a 1/2" pipe for a regular heater.  Distance from the gas main is also apparently a concern, which is why mine was mounted on the other side of the house.

So, now for the tough questions:

1) how many people do you need to "serve" with this heater?
   -- how many bathrooms
      -- with shower/tubs
   -- automatic dishwasher or do you wash them by hand?
   -- ditto for the clothes [hey, it's possible...]

== showers typically run at 3-5 gpm; washers about the same (though the items being washed are less particular about the temp or the time it takes to get "hot" than most humans...)
== sinks may run at 1 to 1-1/2 gpm, though you might consider a flow-restrictor to keep it at 1/2 to 1

== add up the gpm needed to run "all the taps you expect to be open" at any given time to determine the size you need  (or take the shortcut: 7-10 gpm is typical for a family of 4...]
(aside: even though I do have 2 showers, I talked the plumber into a slightly smaller unit since I'm single, so I ended up with one rated for about 5 gpm overall instead of 7)

2) how "hot" do you actually want the water to be?  Note the above "flow rate" is the maximum flow that the heater will heat to (approx) 60 degrees ABOVE the ambient water temperature - even in the dead of winter, I measured the "cold" water at 65 degrees, which is perfect as the recommended output is 125 degrees
(aside: I probably will want to push this up another 5-10 degrees in the winter to counter heat losses in the pipe -- of course, it's also "on the list" to get the pipes wrapped with foam... [just like it's on the list to patch the holes in my swamp cooler's water basin...])

3) gas or electric?
There are some websites that really (really!) knock electric heaters, but that is because they're talking about use in Michigan or similar ;)  Here in california, it's about break-even as to cost vs. effectiveness - if you've already got an electric stove or other high current circuit (50-75 amps), then it is certainly worth considering; otherwise the cost of installing that might make it too expensive [and to further tip the scales to gas, the gas company does offer an incentive; your city may offer an incetive as well]

4) central unit or point-of-use?
This is something that rarely gets discussed or considered - you can get a point-of-use heater for, say, your kitchen sink for less than $200 (maybe even 100 by now) and this will give you endless HOT HOT water in about 3-5 seconds.  Of course, you can augment a full-house system with point-of-use devices to get the best of both worlds.  I've even seen some ads for electric shower heads (though they looked really dodgy...)
4a) point-of-use storage tanks - instead of a 30-50 gallon central heater, these units store about 2-5 gallons heated locally for where they are used.  They have a far lower electrical requirement since they can heat the water relatively slowly rather than attempt to push the temp up 50 or 60 degrees at 1gpm or more

5) for the ultimate in "conservation", consider a recirculation pump to feed the "cold" water in the pipe(s) back to the heater until the "hot" water reaches the tap.  Personally, I think it's just a gimick, and some really serious back-of-the-envelope calculations showed that this is unlikely to actually save you any money (do you realize how cheap water REALLY is?)(*)  [remember from point 1 about flow rates - if it takes "only a minute" for hot water to reach the destination, you would only "save" 1-3 gallons by recirculating it back through the system.  The pump takes some energy to run as well, and if you get down to it, it could cost MORE to move the water through the system than you would have "lost" by letting it drain...]

Tom

(*) water rates: take a look at your bill - notice water usage is measured in some arcane measurement labled "hcf" which stands for "hundred cubic-feet".  Furthermore, I know it doesn't look it when you look at a -5- gallon sparkletts water bottle, but a "cubic foot" of water is over 7 gallons!  1hcf is something like 750 gallons (748 to be exact, at least per this site: http://www.irwd.com/MediaInfo/water_equivalents.php)  Take another look at your bill - around here, you pay either $0.73 or $1.45 for that "hcf"  [first 10 hcf are at $0.73; after that it jumps to the higher rate -- see http://www.glendalewaterandpower.com/rates/water.aspx]

So that's 73 cents for over 730 gallons - that's less than .1 cent per gallon - now you know why selling "bottled water" is so profitable...