WH lifetimes

[Runs with bison]

I went back through the utility records for the only water heater replacement I've ever had (nat. gas). It was in a place I rented for a long time. It wasn't a necessary replacement, the landlord wanted to do it after the plastic drain valve failed. The tank still looked good inside and had little scale or sediment. The existing water heater was at least 8+ years old, don't remember the model. The new one was a Kenmore I believe (Sears install, wasn't my choice.) Gas use in the years before and after were unchanged averaging about 18 ccf/month during the summer. (Same old furnace with pilot the whole time, same showerhead, etc.)

There seems to be some confusion here about terminology: efficiency is not the same as recovery time or effective capacity. This is especially noticeable in electric water heaters as elements foul and burn out.

[Dunbar Plumbing]

In other words, Dunbar, you've got nothing. You refuse to back your claims with anything concrete and those of us with different experiences should believe reality is only what you say it is in your area.

I'll do you one better. I'll continue to track this water heater's gas use until it fails (or I replace it) to see if/when it tumbles. So far water heater gas use is down about 33% in the past year (from 18 therms/month to 12), but I've been reducing wall/pipe losses and hot water consumption by various devices/appliances. I'm approaching half of the Energy Guide rating.



I'm still scratching my head over your electric water heater claim... How again is the electrical efficiency lost? Sure the elements will burn out and quit working, but nearly all of it from beginning to end is going into the tank because it is a resistance heater. The tank can be full of sediment but the heat is still going into the water. The only other place it has to go is surface losses...which are not changing much. Ask an engineer buddy how to draw a box around a system, it's one of the first things you learn.

Now if one really wanted to prove a point about efficiency losses in the gas fired heater, the solution might be in measuring flue gas temps. If the efficiency falls dramatically that heat has to go somewhere during burner operation. And that somewhere is up the flue in a traditional non-power vented model.

Efficiency loss is not necessarily the same as poor recovery or lost working volume.

I'm not "preaching 20 years." Unlike you I don't pretend to know when the water heater walls will begin to leak nor how rapidly efficiency will decline. I'm not trying your "one size fits all" approach.

If efficiency fell off as rapidly as you believe, energy conservation sites and greenies would be all over it.

First of all,

I'm not the 5 post wonder you are.


Secondly, I moderate/admin plumbing forums across the internet, but I just started plumbing last friday.



Second, you don't "grasp" sediment that lines the bottom of a water heater on gas models

you don't "grasp" electric water heaters that can have sediment issues that reach the lower element which is the worker bee of the tank in producing hot water, that when it is submerged in sediment like the picture above shows...the energy guide is wasted print on the heater.

Comprende? Si?

Run with Bison,


Have you never seen an electric water heater element pulled out of an older, sometimes relatively newer water heater at times when a layer of sediment bakes itself to the element, and you hear what sounds like bacon sizzling when the upper thermostat calls for action and you know your water heater is operating?

Are we on the same planet or did I make a wrong turn at Mars today.

Do you think that efficiency isn't lost when buildup is on the elements OR in the bottom of the tank?

DO you think Master Plumber Mark shoved oatmeal in that water heater to make up stories?

Efficiency loss is not necessarily the same as poor recovery or lost working volume.

Are you serious?

So, when a tank's capacity is lost due to mineral buildup, and the conversion is.....wait.


You fill in the blank. You tell me what the conversion is for capacity against ready to use hot water, figure out the # of gallons and then tell me what's the factor used in consideration for doing conversions from gas to electric, electric to gas and what needs to be increased or decreased when doing so.

I'm still scratching my head over your electric water heater claim... How again is the electrical efficiency lost? Sure the elements will burn out and quit working, but nearly all of it from beginning to end is going into the tank because it is a resistance heater. The tank can be full of sediment but the heat is still going into the water. The only other place it has to go is surface losses...which are not changing much.

Did the picture above your post ever make you think that sediment can bury the bottom element...???

Never heard of scale/lime buildup on an element?

You mentioned burn out and quit working...wouldn't that be a dead end statement in reference to knowing that it's going to be instantly replaced to make it operable? Hello?

"The tank can be full of sediment but the heat is still going into the water"


What happens to thermal transfer/dissipation when someone cooks food and beans burn in the bottom of a pot? It traps it, interrupts the cycle of heat rising to the top like all water heaters are designed to do...

that's why cold water enters the tank through the dip tube,

that's why electric water heaters operate by the lower element to heat the incoming cold that rises to the top for the ready to use hot water,


the top element is only for sustaining ready to use hot water when the heater has been inactive for a period of time.


The statements you're making are easy to blow holes through with how much you don't know about the operation of a water heater.


"But my dad works on computers, and he's got tools. We can use his tools and fix things."



If you're going to dance with me, at least dance to the same song with me.

Now I have a reason to use my camera more effectively so the proof is in the pudding to reference what I already know.


You're going to get charged for the ear plugs for every water heater I cut open for the visuals so this "unknown" by years of knowledge comes out and people can point and giggle at the empty statements I just filled for you.


It almost sharpens the pencil for me, it really does when reality and perception get mauled over by someone who can type and argue. I'll be waiting for your response on what you should know in the paragraph above to see if I should stop.

No, I can't do that, I got pictures coming! Whoops, here's one with a little more of that non-efficiency rust buildup:

[Runs with bison]

This is why it can be so hard to communicate with techs/tradesmen, they routinely misapply theory while scoffing at edumacated engineers. Let's review how to draw the box:

Energy efficiency is a measure of how much energy goes into the water versus how much ends up going to the surroundings (flue losses, piping, walls, etc.) If it goes into the sediment (see electric) it is still in the tank with the water. The energy still has to get out either with the water or out through the walls/piping. The effective capacity of the electric heater goes down as the element fouls and if sediment gets high enough to cover it, etc. Efficiency does not. Unless the water in the tank along the walls is much hotter than before, the losses to the environment on electric are going to be essentially unchanged. If you lost X watts out the walls and piping before you will still lose X watts. So for a given amount of hot water usage, your efficiency will be unchanged. Now if you crank up the temp to compensate for lost capacity, you will see greater losses as the delta T to ambient is greater. However, considering that standby losses for electric water heaters are small (90+% energy factor), you won't see much decline in efficiency even then. You are likely to hear complaints about the hot water running out early...been there, done that. Funny thing is, the water heater can work like crap...but still get about the same electrical efficiency per gallon of heated water.

I've pulled out enough electric elements that I have some feel for the sedimentation/scaling aspect. Never had to replace one of the tanks though...they seemed to live on for the dozen or so years I lived with/serviced them. I've scraped out a lot of that carbonate in the bottom. I do recall the capacity dropping off, which was an indication the "death spiral" had begun and that I would soon be replacing the bottom element.

The death spiral in a nat. gas heater will be different than an element failure. Sure sediment will reduce capacity and recovery time at some point. An efficiency loss will result and the wall temps will be higher than before. The question is one of degree. Until that burner is having a really hard time heating the water the energy efficiency is not going to change much. Water's ability to transfer heat is a wonderful thing for those of us with heat exchange design experience. Heat transfer coefficients on the liquid side of an exchanger tend to be an order of magnitude above that on the non-condensing gas side--two orders of magnitude when phase change is occurring. This will handle some scaling before efficiency suffers appreciably. When heat transfer does begin to suffer appreciably the tank is likely starting a death spiral. Flue temps will rise (something you can measure) because the burner will be firing hard, but the heat transfer coefficient is plummeting. Wall temps in the flue will shoot up and the exiting gas will be hotter. This will increase corrosion rates on the flue walls/base.

You can't predict when a wall failure will occur due to corrosion because there are so many types (particularly the exterior wall failure posted earlier--hint: it's not the heat transfer surface, looks like the external weld seam but I could be wrong.) I've seen and troubleshot enough different corrosion/cracking mechanisms in many types of systems and metallurgy (including several grades of titanium, several types of hastelloy, duplex stainless, monel, inconel, brass, copper, aluminum, silver as well as differing grades of stainless and carbon steels), so I know better than to make some sort of bold statement about when something must be replaced without inspecting it.

Putting a six year life on it wasn't smart to begin with because use will also factor in. If one is firing the thing hard and long, cycling it frequently, and/or running high tems I would expect the sedimentation rate to differ from one being run milder. Then there are other factors such as location (water chemistry), maintenance, and water softeners.

[Dunbar Plumbing]

Ahh you're an engineer. Now I know why this thread interested you so much. You know this situation from an entirely different angle than what I represent.


However, (and I've said this countless times) that I never retract a statement on the internet. I stand by my 6 year statement because soon enough I'm going to get my hands on one with a camera and start disecting these jewels to show the various situations from different areas that water/pressure/mineral content plays havoc on a water heater and its warranty.

What sucks is I just had a scrap guy take away 9 water heaters I had sitting at the shop. Those would of been a great show and tell as they all came from differing cities, all had a reason why they were replaced, with the common denominator of they all leaked but one. 1 customer took a preventive approach and the sediment buildup was ridiculous.



In your statement about sediment on a gas water heater, If a thermostat is set to 150 degrees to produce hot water for an aging unit, and the customer is complaining of "running out of hot water" in these conditions...

Where is the efficiency of that aging water heater, even though it is not leaking.

Property owners command hot water demand, they almost always don't care about the workings of the situation, they just want hot water like a new tank offers.

That thinking enters a different form of thinking when the end user considers a tank "lasting" a good deal from a consumer perspective if they feel that the unit is operating at a cost efficiency the same as the day it was installed. That's the point I'm making and replacement, especially with the new energy guide requirements (Higher R Value ratings) on these tank water heaters make the older ones an unwise choice, especially when a 20 year old water heater will have rail thin insulation wrapping the tank. That's a no brainer that the cost to operate that unit, along with what's hidden inside that tank collecting, affecting the operation of that unit.

[Runs with bison]

Dunbar,

Sounds like we are closer to being on the same page now. I don't doubt that you primarily see the units that were/are badly scaled/sedimented and need replacement regardless of age. I expect you to, that's why folks call you. Unfortunately, through no fault of your own this will produce a skewed distribution. How many calls do you get from customers or non-customers who just out of the blue say, "My water heater is running great after X years, just thought you might want to come see it!" I'm betting you don't, just like plant superintendents never called me to show me how beautifully their equipment was running before it started misbehaving. I got called for help when things were in the ditch as did the mechanics, instrument folks, and other support staff. Often it was for processes I had never worked with, and equipment that was new to me. Afterward, if I wanted to find out how things turned out, I usually had to call them (that typically meant it worked.) They would remember to invite me to some BBQ victory celebrations though. On the other hand, if it didn't work they were sure to let me know...

I also do not doubt that when gas heaters enter that death spiral their efficiency drops. But the death spiral will likely differ from normal aging where the efficiency hit will be modest (like I said, I've so far not been able to measure it from background on water heaters I've used.) Having to crank the thermostat up is a warning to the owner that the heater is having trouble. Leaks of course are the other obvious indication that time is up.

I am sincere about wondering about flue gas temps (for non-power vented units.) This should probably be measured an inch or so below/inside the heater's exhaust after a minute or so of burner run time so that external draft into the flue at the top of the heater is removed as a variable. This is one of those things that would require a bit of a history to be useful. Could be a wild goose chase. Figuring out a correlation of flue temp with fouling could be quite useful for both energy conservation and equipment changeout. Changing out equipment early wastes money, but changing it out about the time the death spiral starts could save folks a lot of heartache, and money.

[master plumber mark]

[quote=
I also do not doubt that when gas heaters enter that death spiral their efficiency drops. But the death spiral will likely differ from normal aging where the efficiency hit will be modest (like I said, I've so far not been able to measure it from background on water heaters I've used.) Having to crank the thermostat up is a warning to the owner that the heater is having trouble. Leaks of course are the other obvious indication that time is up.



[SIZE=3]in our town I get 3 to 5 calls a week wanting me to come out and flush the tank for them.... I tell them that it will be $150 to fool with their 9 year old gas heater that is rumbling all the time and I also tell them that my work is guaranteed for only 30 days... [/SIZE]
Then it begins to build up all over again..


they also want me to try the vinegar suoltions in the tank to clean it and I tell them that it can do more harm than good to strip the lime out of a 9 year old rumbling heater.exposeing any old metal cracks to the water can usually accellerate a leak..

.. and when I tell them its worth about $275 to do this they usually opt for a new heater...

when you hear the banging and rumbling, the heater is trying its best to let you know its getting over the hill...

[GoldMaple]

I had to respond to this post. I'm in the middle of researching water heaters because I'm in desperate need of a new one. My water heater still works but I can't imagine how low it's efficency rating is. It's 27 years old... (John Woods) Here's the thing, I'll bet that it's half full of scale. I have a water distiller that I descale 2 times a year and when I do it has a heavy layer of scale in it. After descaling the unit a gallon of water is distilled in less time.

My water heater has never been cleaned. I don't even know if it's possible and simply draining the tank is most likely next to useless. I base that assumption on the cleaning of my distiller, where the scale is hard packed and stuck to ALL surfaces. Every once in a while a chunk may break off but it's too big to pour out the drain spout. So, it accumulates and I'm able to clean the distiller because it's small and has a lid that opens.

I'm a typical home owner when it comes to water heaters. For the most part I just ignore it. As a result my water heater probably looks worse than this one inside............

[Thatguy]

water heater
27 years old

If it's gas it has outlived 96% of its peers.

[GoldMaple]

Yes, it's a gas heater and I'm now just realizing that it could blow at any moment....... Based on everything I've been reading a Bradford White would be a good replacement so I'm tracking down dealers in my area and will get one installed soon.

[ferd]

Our WH was installed in 1972! Nothing ever comes out when it's drained.
So I guess we are ahead of the curve. I credit the longevity with it heating at 65k btu's and we have a softener on well water. We never run out of hot water! I think that by heating at this high rate it is not as efficient but it keeps everything dried out. I've been looking for a new one but can't find a fifty gallon with more than 45k btu short of going commercial. When we change it I'll cut it open to see what's inside.

[Thatguy]

Our WH was installed in 1972!

If it's gas it's the oldest I've heard of.

[gusherb94]

The water heater in our 3 unit apartment building is 13 years old, still going well. 50 gallon State.

Well after 13 years and being used very heavily the State water heater finally died on Tuesday........It sprung a nice leak in the flue, put out the pilot, and left a nice puddle in the basement.
Of course being it's an apartment building we can't be out of hot water for long so the heater was replaced, and no a pro was not called (even though I would have preferred that myself as not to have the day before thanksgiving spent on that....) but I and my dad got the new Bradford White 50 gallon high recovery heater in and working, it needed a bit of repiping to make it all work and the flue right off the water heater was replaced since it was all rusted out.
But anyway old one lasted 13 years, easily ran out of hot water. New one is same tank size but high recovery, and it should hopefully never or rarely run out.

[gusherb94]

Friday I went to the building, to the apartment that's our's, and tested the new water heater's capabilities....
So what I did was first started the dishwasher, then took a 20 minute hot shower. By then water heater temp was down to about 110 by the time I turned off the shower (thermostat set to 140), dishwasher filled and emptied a few times during that time as part of it's normal cycle.
Then to top it off I decided to run the top load washer at max water level on hot with warm rinse, about 5 minutes after the shower. hot water temperature hovered at about 110 during the whole time it filled and once it stopped filling the heater caught up again...fast.

So overall the new water heater does about what I expected, it supplies plenty of hot water for intense hot water use between tenants and after some long use hot water runs down but not out.... Just what I wanted, and once hot water use susbides a little the tank catches up more than enough for another shower or the rinse cycle of the washer, fast.

So overall I'm very happy with the hot water supply now. Next up in who knows when time will be the rusted through 1" water main in the basement...

[Doherty Plumbing]

Next up in who knows when time will be the rusted through 1" water main in the basement...

A bit off topic but an ounce of prevention is worth a pound of cure.... I'd fix that bad boy before it blows.

[JMMJR]

This thread was a very entertaining and educational read.

I did a drain/flush/refill on my 80-gallon Bradford White electric today. It's only 4 years-old. It blew the lower element last year, so I had to drain it. I replaced both of the cheap elements that were in it with nice low-watt-density ones. I drained it and took a look at the elements. They had minimal buildup and I got minimal deposits out of the tank as well. I'm going to drain it every year from now on.