The Tank › New heater time(?)
- July 22, 2007 at 7:09 pm #6888BillTParticipant
Thanks so much for the wealth of useful information you have assembled here. Of course, there are always just a few more questions from the uninitiated, so here goes:
The $188 50-gallon Master Plumber (TruValue brand) electric water heater that we installed 16 years ago suddenly started providing much less (and somewhat cooler) hot water this past week – from what you say here it sounds as if probably either the lower element or the dip tube failed. As it was not serviced at all over those 16 years, now that we know better we consider ourselves quite lucky (both for its longevity and for the relatively benign nature of its current failure) – but suspect that trying to spruce it up properly in place would take more effort (with no guarantee that it would last much longer anyway) than simply replacing it, and a comparable Sears or Home Depot unit costs only $230 – $244 (I will take a look at the old unit afterward to see whether repairing it as a potential emergency replacement might make sense, though).
The price we pay for LNG has nearly doubled over the past 3 years, so that option now enjoys at most a 20% – 25% energy cost advantage over electric – with far higher up-front costs (not just for the heater, but for the long pipe run from our tanks and the required venting).
While I understand why you might be reluctant to display brand favoritism here, just in case others have comments I’ll observe that a very superficial anecdotal survey of electric heaters from the major names on the Web suggests that Kenmore (I guess from A. O. Smith these days) enjoys a fairly good reputation (the three product reviews on the Sears Web site associated with the model we’d likely want are *dreadful*, but one of them is clearly for a gas-fired unit), with Rheem not far behind (though with their GE brand perhaps a bit farther back) and Whirlpool bringing up the rear. Kenmore (“Roto-Swirl”) and Rheem both advertise dip tube configurations that seem to function similarly to your curved tubes; I’ll have to wait until tomorrow to find out what flavor anode Kenmore has.
My questions are:
1. Even if the manufacturer’s dip tube does not perform the same function as yours, given that our existing heater survived 16 years’ worth of sediment build-up without ever being drained at all would it be reasonable to suspect that with a yearly brief flush there would be little reason to replace that dip tube until such time (perhaps a decade from now) as concerns about its deterioration would make replacement prudent anyway (and is the Sears ‘PEX’ tube material anything special in this regard)?
2. The units we’re looking at come with pre-installed relief valves. Is there any reason not to remove this (and the anode) to add teflon pipe tape to make future replacement easier?
3. Another site recommends using only a hex socket or box-end wrench to remove the anode, to avoid stripping its nut (and you yourselves mention that considerable force may be required). Is that your experience as well (i.e., should I try to find one rather than take a shot with the Craftsman 12-points that I already have)?
4. I used 3/4″ CPVC for the original relief-valve overflow piping, but 1″ PVC for the pipe out of the drain pan (I guess thinking that if normal PVC was OK for the rest of the house drains it should be OK for this one as well). Since the heater is located in our attic, I *really* wouldn’t want this pipe to melt: should I be concerned enough to replace it (which would be a bit difficult, given how it runs)?
5. We’ve run our existing heater at 120 F (water source is a deep well), but I would think that the sediment in the bottom seldom even gets near that temperature (since the lower heating element is part-way up the tank and the dip tube at least used to introduce cold water near the bottom; might be different with a gas heater nearer the bottom, of course). Legionella is said to grow robustly at temperatures up to 115 F, and to take several hours to die even at up to 140 F, so it would seem dangerous to assume that a setting even as high as 140 F would do much good if it breeds in the bottom of the tank (at significantly lower temperatures) and then makes only a quick trip at higher temperatures through the lines before emerging at a fixture. So is there really a good reason to set the thermostat higher than 120 F (since there are multiple other reasons such as economy and component longevity not to)?
6. If we go with the Sears unit it apparently has an option to run its elements at 3800 W rather than 5500 W (the stated purpose being to accommodate existing lighter-gauge wiring). While there’s 10-gauge wire running to the heater, would this make sense anyway to prolong element life (or for some other reason)?
7. Does adding a second anode serve any purpose other than to extend the time between anode replacements (and extend the time before the first anode inspection may be prudent)?
Again, thanks so much for all the material here, and for any specific insights you might have on the above questions.
BillJuly 23, 2007 at 7:42 am #6890energyexpertParticipant
A lot of good questions.
For additional outside the box info check out http://www.marathonheaters.com (http://www.chec.coop)and http://www.howardharrisbuilders.com. The Marathon is a fiberglass tank so it has no anode. Harris WH is a plastic insulated holding tank which runs a finned copper tube through the tank to absorb BTUs also with no anode. Your bacteria question is interesting because at 3 gpm flow, your domestic water is in the Harris WH less than 10 seconds.
As to element longevity. Ohm’s law states for a resistive circuit, the current is directly proportional to the voltage. Cut the voltage in half and the current goes to one half; power goes to one fourth. I currently have my 105 gallon Marathon wired at 120 volts and wired for simultaneous operation. Element output is 1125 watts each but rated at 4500 watts, 240 volts. They should last forever.
As to operation costs. Time of use rates are available in Asheville, NC. I heat my water off-peak only at $0.045/kWh. This is cheaper than natural gas.
DavidJuly 23, 2007 at 1:19 pm #6891Randy SchuylerKeymaster
None of the “self-flushing” dip tubes the manufacturers include actually eject sediment from the tank. They are all closed on the end, and attempt to stir up the water so much that sediment doesn’t get a chance to settle. We have our doubts that works.
As to whether you need a curved dip tube or not kind of depends on how hard your water is. If, after 16 years, you never had sediment bury your lower element and burn it out, there may not be enough hardness to worry about, although well water is usually pretty hard. But flushing without a curved dip tube doesn’t work very well. The vast majority of sediment stays in the tank.
You answered your own question on the relief valve and anode. They’re both more likely to come out easily now and they’ll definitely be easier to take out later if they have Teflon on them.
You are right about the second anode. However, it is quite easy to completely forget about checking the anode at the right time and having two provides you some insurance against your faulty memory.;)
Go ahead and try your 12-point socket, but back off if it feels as if it’s slipping.
We think the thermostat should be set so that you get 130 at the tap, as we say elsewhere on the site, as a compromise between scalding and legionella, and that 120 is too low.
Randy SchuylerAugust 5, 2007 at 2:17 pm #6955BillTParticipant
After various delays and hemming and hawing, we decided that a new $244 Rheem/GE heater from Home Depot was probably a better approach than going however many days without hot water we’d have to to remove the old heater from the attic, clean it out, and then (if everything looked OK) lug it back up and reinstall it. And since HD happened to have a 10% off coupon…
The new installation went smoothly (even the old 24″ bendable copper tube connectors were reusable, with gentle handling), and the old heater indeed turned out to have enough lime build-up in the bottom to have reached the bottom element (which was burned out and so distorted that it could only be removed inch by inch while squeezing it together with pliers). It took forever to get all the sediment out, even after having opened up the bottom element hole and removed the plastic drain valve – we had to place the tank drain-down on its side, squirt in a high-pressure stream of water through the top holes, and use a bamboo rod (which I hope didn’t scratch the inside tank coating) to break up the sludge (the tank had sat empty for a couple of days, which probably didn’t help the situation). Many of the lime pieces were far too large to have ever made it through any drain valve; some were too large to fit through the drain valve hole: guess that’s what happens after 16 years of neglect.
The old dip tube looked fine, though I couldn’t remove the assocaited nipple without thread damage (for some reason it was installed far more tightly than the hot-water combo rod/nipple). The (magnesium, full-length) combo anode was mostly still there: a half-dozen sections along its length (the longest about 4″ long) had partially wasted away (and then been covered with lime build-up) and the rest just had a think coating of lime on it – so it didn’t appear to have completely ‘passivated’ but certainly didn’t seem to have been doing much (hopefully because there just wasn’t much to do).
After finishing the clean-out we drained out the last of the water, plugged a vacuum-cleaner hose into the lower-element hole, and sucked low-humidity outside air through the tank for an hour to try to dry it out thoroughly (to minimize the likelihood that it would rust while sitting idle).
So perhaps the old heater has some life left in it after all – we never saw any sign of rust in its output. Any suggestions on proper storage would be welcome: I’m not sure that it’s very feasible to store it full of water to prevent rust damage, but perhaps thoroughly drying it out (and possibly introducing a dessicant) just before sealing up its apertures would be useful.
Thanks once more for the inspiration which this site provided: we wouldn’t otherwise have had a clue what we were doing.August 5, 2007 at 3:33 pm #6961Larry WeingartenParticipant
Hello: Storing an older heater dry can work if you can get rid of all the moisture and keep it gone. Your dessicant idea is something I have not tried (but imagine could work). I’d seal the tank up with a packet of silica dessicant suspended inside. I’d want to do this so that the packet was easily removeable and so that it didn’t have any chance to contact the tank. It may get wet with time and if it’s sitting in contact with the tank, could rust there. Just a thought 😎
ps. A note on the outside of the tank reminding you of the dessicant might not be a bad thing.
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