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water heater insulation - help
Old 05-08-2008, 01:29 PM   #1
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water heater insulation - help

Before I say anything else (and in case you're wondering why am I asking such silly questions), you should know I basically know nothing related to home improvements/maintenance.

Anyway, in an attempt to reduce our energy costs, I was all set to get some insulation and wrap our hot water heater... So, I went downstairs to check on the size of the tank and to see first hand how hot (on the outside) this thing gets. In my mind at least, the hotter the surface temp, the greater will be the potential energy loss. Imagine my surprise when I touched the tank and it was very cool; not hot, not warm.

So, here's my question. Do I still need the insulation? Do all tank-based water heaters benefit from insulation? Is it possible that certain tanks/newer models include sufficient internal insulation?

If it helps, I looked it up, out heater is about 7 yrs old.

Thanks!
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Old 05-08-2008, 01:42 PM   #2
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My 9 year old water heater is located in my uninsulated garage, right next to the garage door. So I thought I'd better buy one of those water heater blankets at Lowe's and get this puppy insulated to conserve energy. A few month later I called my plumber to replace one of the heating elements on the heater and he told me that my water heater was already insulated enough on the inside and that I really did not need to add a blanket around it. He showed me the insulation inside and it was pretty thick. I did not see any noticeable difference on my electric bill after adding the blanket.
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Old 05-08-2008, 02:03 PM   #3
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My water heater specifically says that it does not need a blanket (A.O.Smith); it feels cool.
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Old 05-08-2008, 02:59 PM   #4
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I agree, if it doesn't feel hot on the surface, it's not leaking much heat.

Might be worth checking the top and bottom though, in case they aren't insulated. I know my top is fine, I keep forgetting to check the bottom.
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Old 05-08-2008, 03:13 PM   #5
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Benefit of extra insulation depends on type of heater. Electric-more benefit.Gas- not so much- it has a constant draft through the chimney.
Even if the maker say no extra insulation is required, you still benefit from adding more. Heat loss is dependent on temperature difference of water temp to ambient. The longer more complicated the heat path to cooler area the better.
Having said that, you will find after adding extra insulation to outside of tank that after a few days if you put your hand between the new insulation and tank housing, it will be toasty under there. Clear indication of heat savings.
Cost recovery may be a year or two. Insulating tank is far more cost effective than putting a timer on it. By several orders of magnitude.
Cheers and happy savings.
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Old 05-08-2008, 03:45 PM   #6
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We have TWO 36 Gallon HWH in the heated basement so no blanket is needed - also be careful with the newer Gas HWH as they have basically sealed the heating element with two venting areas on either side towards the bottom and you do not want to seal these vents up.


Since it is only DW and myself and we do not use the big jacuzzi tub in the MBR and after speaking with a plumber (who was actually installing a new gas HWH in my daughters home yesterday) I just shut down one of the HWH - I think that will save more energy for us. Additionally, as the plumber suggested, when that one dies just switch over to the other one (redundancy).
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Old 05-08-2008, 05:16 PM   #7
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You will generally cause problems with a modern water heater by adding insulation to it.

Where you can get some nice savings is insulating the hot, cold and pressure relief pipes. If your water heater has semi-flexible connectors, adding a "gooseneck" to the hot water line on top of the heater can save you a bunch of heat loss. Basically you want to add another piece of the flexible line so that it goes up from the water heater, bends back down in a u-turn, then goes into your original pipe. Hot water rises up into the top of the gooseneck, then stops. This prevents the rest of the hot water pipes in your house from acting as a radiator.

When replacing a WH, make sure you have a higher efficiency unit and the insulation value is R-16 or better. Hint: nothing sold at lowes or home depot is high efficiency and high R-value.

The Best Water Heater: Some extra parts make all the difference

I like the sears kenmore 12 year models. R-16, .62-.64 efficient, reasonably inexpensive, made by AO smith.
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Old 05-08-2008, 05:29 PM   #8
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Hint from my plumber father and brother: If you want your water heater to last longer, periodically drain a few gallons of water from the draincock near the bottom of the tank. Helps remove the sediment that causes corrosion of the bottom.
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Old 05-08-2008, 08:36 PM   #9
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You will generally cause problems with a modern water heater by adding insulation to it.
With an electric water heater? What problem(s)?

OP, if your water heater is electric, consider placing it on a one inch thick piece of styrafoam insulation. Most electric water heaters are only insulated on the top and side; when placed directly on concrete, they tend to tranfer heat to the slab
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Old 05-08-2008, 08:43 PM   #10
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Quote:
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With an electric water heater? What problem(s)?
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So I thought I'd better buy one of those water heater blankets at Lowe's and get this puppy insulated to conserve energy. A few month later I called my plumber to replace one of the heating elements on the heater and he told me that my water heater was already insulated enough on the inside and that I really did not need to add a blanket around it.
This.
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Old 05-08-2008, 08:58 PM   #11
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This.
Hmmmm. I think the plumber was BS'ing a bit if he was implying that adding insulation caused the heating element to burn out prematurely .

If it is indeed true, I would love to see research explanation. At most, adding extra insulation to a modern electric water heater is a poor investment yielding little payback.

Adding the thermal trap (gooseneck) is a good idea though
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Old 05-09-2008, 05:40 AM   #12
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So from what I see in this (confusing) thread: Forget the insulation and just cut the temp back about 5 degrees, you will save more! And if you really have a dishwasher that requires a higher temperature, learn to wash dishes?

BTW the GAS RUDD that was installed the other day, in my daughters home, specifically was labeled as "self-cleaning". I was skeptical about that as I have always done the "drain a tad annually" bit. The way the plumber explained it was that there is a plate in the bottom that caused the sediment to be flushed upward before it could settle in any amount on the bottom of the heater - actually just went back out with the hot water to the facets - probably a good idea to remove the strainers in them annually and clean them out anyways (but that is another whole subject).
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Old 05-09-2008, 08:13 AM   #13
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Wow, lots of great feedback. Thanks guys!

Well, I have decided not to bother with the blanket (we have a gas heater, btw), but will wrap a few feet of all pipes in/out of the heater.

CFB - I love the idea of the gooseneck! So simple and effective, it makes you wonder why such installations are not "standard"? Unfortunately, quite a bit of welding is required to add one to our set-up; so, maybe next time.

Achiever - Thanks for the tip about draining a bit of water every now and then -I have never heard of that.

One more thing... how long does an average gas heater lasts (we have Bradford White)? Also, is there a way to tell it's about to break down and we're on borrowed time?

Thanks again!
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Old 05-09-2008, 09:00 AM   #14
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Wanna save even more? Get a tankless on-demand gas water heater.

Caveat: You never run out of hot water....parents of teenagers should be aware that what they gain in energy efficiency they may lose (and possibly even more) in longer teen showers.

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Old 05-09-2008, 09:49 AM   #15
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I havent ever been able to figure out how to get a payback out of a tankless. In new construction arrangements its almost a break-even but in retrofits you're looking at $1500-2000 installed for a tankless big enough to handle two service demands. And despite their reputation for being more reliable than tank heaters, I've seen plenty of them break down.

The life of a HWH? Depends on your water quality and your luck. Older WH's had big honking thick tanks and took a long time to rust out. Newer ones are of course cost reduced, thinner, and every once in a while you get a bad one and well, the QA costs have been reduced too. Water heaters depend on a rod of 'sacrificial metal, which may be aluminum or magnesium. The elements in your water that might attack the metal tank of the WH elect to attack the softer metals in that anode rod and eat at it. Eventually it gets completely consumed. At that point you have to replace it or the corrosive elements in your water will begin eating the tank. Generally WH's come in 6, 9 and 12 year 'warranty' versions. These are often the same, with the difference being a 6 year has one rod, a 9 year has one rod and a half rod thats also the hot water outlet pipe, and the 12 year has two rods, one in the hot water outlet.

If you have good water, a 6 year WH might last 18-20. If you have bad water, it might last 4. You'll know when it goes, it'll start leaking. Signs of rust or water on top of the unit near the pipe connections or rust/water near the burners are signs that its time to replace the WH. Another sign is a lot of steam coming out of the vent stack, which means you've got a water leak in the gas duct that runs up the middle of the WH, and the gas flame is converting that to steam. There usually isnt a lot of visible condensate in a gas water heaters vented gasses.

You can replace the anode rods with new ones, but unless you removed them when the WH was new and put some teflon paste on the threads, the things are likely to be rusted in place. A 3' long wrench might get them out but you might also just sheer off the head or rip the whole mess out of the water heater, ruining it.

I heard a lot of stuff about the aluminum rods traditionally used in WH's being one of the possible sources for Alzheimers. So I make sure I use WH's with magnesium rods...just to be sure. I've also heard rumors that old water heaters can be loaded with temperature resistant bacteria and other growths that may cause a bad taste or health issues. Some recommend turning the WH temps up to full tilt for 4-6 hours once a year or so.

Generally the higher the WH temps, the shorter the WH life, but not by a lot.

When replacing a WH, its a good idea to consider installing a thermal expansion tank. These are little bladder filled tanks, look like a small gas grill propane tank, and they're filled with air to a pressure matching your houses internal water pressure. Should an overpressure situation occur from heating the water, the tank will absorb that. Some homes water main valves allow overpressure backflow into the water system...many newer homes or ones that have had their water main valve/meter are non backflow systems and are 'closed'. I've seen closed systems with a big water heater and no expansion tank hit 90-120PSI. Most household plumbing can only take up to 80. Some plumbers overcome potential overpressure situations by installing a cheap inlet valve in a toilet somewhere in the house, and when the pressure goes over 80, that toilet will cycle and let off the overpressure. Which works great until the homeowner replaces that valve with a good one.

So if you hear your toilets cycling, your plastic refrigerator icemaker water line keeps breaking, or you have excessive plumbing leaks...thats probably the problem.

Cleaning WH's is another area of dissension. Most WH's are actually fairly hard to clean sediment out of. Opening the water valve with a bucket under it or a hose will only get some of the sediment. A pretty small amount. Turning the water off, draining it entirely, then turning the water on can create some turbulence and remove some more...but its a lot of stress on the tank and the stock el cheapo drain valves they put on most WH's these days will absolutely start leaking on you if you fool around with it too much. Some WH's have 'rotoswirl' or self cleaning inlet tubes. They sort of work a little bit. Some companies make replacement cold water inlet tubes you can install in a new WH that are allegedly better than the stock self cleaning tubes. Most plumbers dont feel these work very well either but they're better than nothing. One plumber I know suggests just leaving the damn thing alone as he feels the draining process may cause more problems than it solves.

Its almost a certainty that a 12-15 year old WH, even one thats been drained regularly, will have a foot or two of rock hard sediment in the bottom, which will inhibit efficient heating and reduce the capacity of the heater.

Given that WH replacement labor is often as much or more than the WH itself, it makes sense to find and install a quality product that will last. Spending $400 every six years to replace a $300 water heater makes little sense when you can spend $400 every twelve years to install a $400 water heater.

You can save a little money by buying a six year heater and buying a second anode rod to install in the hot water outlet yourself just prior to installing the WH. In effect you'll be making a 12 year WH with a 6 year warranty for about $80 less.

As far as adding a blanket causing problems with an electric WH? Well, many of them tell you not to put a blanket on them, I've seen a lot of unusual failures in both gas and electric heaters after a WH blanket is put on them, and I'd imagine the manufacturers who stamp "do not put a WH blanket on this heater!" presume that you wont and may have components inside or on the heater that arent rated for an increased temperature or are reliant on exposure to the air. Rather than spend $30 to save 50c a month in electricity, I'd rather replace the electric WH with a high end unit like a Marathon or do a gas conversion, install a 12 year .64 gas WH and save myself a whole bunch of money over the next 15 years.

And THATS just about everything I know about water heaters, other than the fact that they're ridiculously heavy...
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Old 05-09-2008, 10:33 AM   #16
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Hmmmm. I think the plumber was BS'ing a bit if he was implying that adding insulation caused the heating element to burn out prematurely .

If it is indeed true, I would love to see research explanation. At most, adding extra insulation to a modern electric water heater is a poor investment yielding little payback.
The plumber never implied that the blanket was responsible for the heating element to burn out. He merely thought that it was quite normal for a 9 year old electric water heater to require a new bottom heating element (the one that does most of the work). Since the heating element had to be replaced only a few month or so after I installed the blanket, I personally thought that there was a link between the 2 events, but my plumber did not think so. Actually even though he thought the blanket was not needed, he put it back on the heater after completing the repair, so clearly he did not think it would hurt the heater at all.
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Old 05-09-2008, 11:17 AM   #17
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Whether or not the blanket helped it along or not is tough to tell. What I do know is that most WH manufacturers do not recommend using one, most will void your warranty if you use one, they may cause wiring to overheat, and they certainly can mask the early signs of tank failure. One thing I do know is that added insulation near the thermo port on a water heater can cause the unit to misread the water temperature and excessively cycle the element, which would certainly lead to an early demise.

And if I were your plumber and just got to do an easy and lucrative replacement of an element, I'd put the blanket back on too!

I guess if you had a 20 year old cheap, poorly insulated electric unit in an unheated space, and lived on a limited income with six starving kids and couldnt afford to install a better unit, then it might save you a few dollars.

I remember looking at a kenmore blanket in Orchard Supply Hardware a few months ago (Gabe was playing on the tractor next to it). In reading the box it basically said "Your water heater manufacturer probably doesnt recommend you use this, and neither do we!" I remember it because its one of the first times I've read a product box and had it essentially tell me to not buy or use the product.

But if it still seems like a good idea, you oughta get one. And I have some ISM/OSM for sale at an excellent price.
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Old 05-09-2008, 09:16 PM   #18
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We have tankless in our apartment, I think it is a paloma, and really like it so when we built our home we put two in (one for each end of the house), but could only find a Bosch/Takagi at the time. I think it was around $800 each but can't remember for sure...may have been a bit more. Each runs 2-3 high volume uses with no problem and will handle more than that if the volume of each is a little less. Where we built, we have to use propane, and the price has doubled in the past few years so we'll get our money's worth, no doubt, unless DS and DD decide to go to a local college (think 20 minute showers...each).

I can say that when you have 10 guests in the house, tankless is the only way to go. The 30 or 35 gallon tank, natural gas water heater we have in the old house takes way too long to re-heat.

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Old 05-09-2008, 09:38 PM   #19
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When I plumbed the house for gas I replaced the old electric water heater with a new gas one. Like CFB, when I did the math a tankless one didn't make sense. Plus, our water is hard and the installation of the softener means the water going to the WH isn't hard, but has quite a bit of sodium in it. This didn't sound like it was going to help the longevity of my water heating appliance, and I'd rather replace a conventional water heater after ten years than a tankless model costing twice as much.

A high-efficiency WH also didn't quite make sense, so I installed a regular model (i.e. no separate external combustion air, regular metal flue, not a PVC one, etc).

One other tip: Be sure the guy who replaces your Wh installs a drip pan, and that it drains to someplace that makes sense. These pans are required by code in most places. Every water heater will eventually leak.

Oh, and put a high-quality valve in the line leading to the WH if the one there now is old and rusted in place. When that water heater DOES start to leak, you'll want to be able to turn off the water.

Oh (again),--for you folks who want to try draining the sediment from your tank (which I don't plan to do, after glancing at the plastic POS drain valve on my WH)--be sure to turn off the water heater before you let any water out. I don't know what bad things might happen with a gas unit, but an electric element that turns on when not covered with water will burn out in a matter of seconds..
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Old 05-09-2008, 09:48 PM   #20
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Yeah, its pretty worthwhile to spend $10 and replace the cheap plastic valve with a nice metal ball valve.
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