My first thought was that one of the electric heating coils in the water heater has stopped working.

Other thought was that there may be a lot of scale buildup on the heating coils that needs to be cleaned off.

Another odd thing recently, seeming to coincide with the drop in maximum temperature of the water, air bubbles have been coming through the fixtures consistently now. It seems to be restricted to the hot water side of the faucets.

What should I look for here? Drain the water heater and pull the coils out? Is there a way to test them?

Other thought was that there may be a lot of scale buildup on the heating coils that needs to be cleaned off".

You're right on those points...

If you have a dead element that can be replaced.

If your water is hard and you haven't been routinely draining your water heater then you probably have a considerable buildup of solids at the bottom of the tank that may be restricting the flow of the drip tube.

Hard water, especially well water, kills water heaters prematurely along with plumbing, fixtures, and appliances.

Good time to cure the disease instead of treating the symptom... it'll cost you a lot less money in the long run.

When was the last time you had a comprehensive water test done?

Are the water heater coils something I need to get specifically from AO Smith? Or are they generic in design and can be picked up at the hardware store?

Just had the water test results emailed to me the other day. High in sodium. I will eventually be adding a water softener, the suggestion was to go with a unit that can use potassium.

Here are the highlights from the water testing.

HIGHLIGHTS:
Hardness: the calculated hardness of this water sample exceeds 120 ppm. The water is, therefore,
considered hard. Water hardness is related to the amount of calcium, magnesium and other minerals in the
water. Hard water does not pose a hazard to health, but it can cause scale formation in pots, water pipes
and water heaters. It can also interfere with the cleaning action of soaps and detergents, forming film on
skin, clothing and fixtures.

Saturation Index: Predicts either potential for corrosion or scaling properties of water. The SI is balanced
and no treatment is needed.

Conductivity: Conductivity is a measure of the ability of water to conduct electricity. Conductivity increases
as the amount of dissolved ionic solids increase and is sometimes called "soluble salts". Dissolved inorganic
compounds are relatively good conductors, while dissolved organic compounds are poor conductors. The
conductivity of distilled water is usually around 0.5 to 3 uS/cm and most drinking water in the US ranges
from 50 to 1500 uS/cm.

Sodium (Na): the concentration of sodium in this sample exceeds 20 parts per million (ppm). EPA has not
set a maximum drinking water contaminant level for sodium; however, persons who consume this water
regularly and have a history of heart problems or high blood pressure should consult their physician.
Sodium can be removed from drinking water using a point-of-use demineralization system such as
distillation or reverse osmosis (RO).

Arsenic: is present but at low levels. EPA suggests treatment if level is 5ppb or higher. The value in your
water is 4ppb. Arsenic can be removed with a reverse osmosis unit or distillation.

Sulfate (SO4
2-): is present at levels that may cause cloudiness, discoloration, or white to faint yellowish film
in pots or cups when heating the water or using it to make hot drinks such as tea. Sulfate, in combination
with bacteria in the well or distribution system, may also produce a "rotten egg" odor or black deposits on
plumbing and fixtures. Also see above. If such problems are not observed then sulfate may be left
untreated.

Don't need a dissertation just the numbers.
Hardness
Iron
Manganese
TDS
Sodium
Bacteria
Nitrates

Arsenic at 4ppm is borderline and you should consider treating that.

Are these test results coming from a certified lab?

Living on a well requires more knowledge and more maintenance than living on a water system does. You are responsible for making the water nice and SAFE.

Any ion exchange water softener can use either NaCl or KCl as a regenerent.

The upper heating element, 4500w, had some scale, but was easily cleaned by soaking a while in vinegar.

I used a reducer on my wet/dry vac that goes down to 1 inch. Then I cut a 30" section of garden hose and taped that to the reducer.

I proceeded to vacuum out the deposits through the lower heat element hole. It took a good hour to get about 98% of it out. I estimate that it was about 12-15lbs of loose deposits. Mostly small flaky stuff, but some bigger chunks as well.

I checked with a flashlight, and there did not seem to be anything really adhering to the tank, just mainly loose particles.

Ace Hardware had a replacement element of proper wattage this time. Those went back in and the tank refilled partly and flushed out a few gallons oof murky water. Then I let the tank fill completely. The house faucets opened for a few minutes to purge the air. Then I got the electric back on, checked for leaks, all was fine.

Yes, it was a certified water test lab.
Total Hardness 424
Hardness 297
Iron negligible
Manganese negligible
TDS 347
Sodium 28.4
Bacteria 0
Nitrates 2.42

Numbers are good, now the denominators? 424, 297, 347, 28.4, 2.42 WHAT? Ounces, gallons, gpm, mg/l, ppm, ppb? I know what they are but other people need to understand.

You have hard water with considerable TDS and should be looking at a correctly sized water softener treating the whole house and an RO under the kitchen sink.

You'll cut down the wear and tear on your plumbing, appliances, and fixtures. You'll use less soap and detergents and your clothes will last longer.

---------------------------------
EPA Approved /Analytical Method
Analyte
Result

Bacteria

m-ColiBlue24® Test
Non-E. coli Coliforms
0 cfu/100 mls

m-ColiBlue24® Test
E. coli(Escherichia coli )
0 cfu/100 mls

m-ColiBlue24® Test
(Red plus Blue)
Total Coliforms 0 cfu/100 mls
-----------------------------
Total Hardness
425 ppm (parts per million)

Hardness (G)
297 ppm

Iron, Total (Fe PP G)
negligible ppm

Manganese, HR (Mn PP G)
negligible ppm

Total Dissolved Solids
347 ppm

Sodium (Na G)
28.4 ppm

Nitrogen, Nitrate (G)
2.42 ppm

Arsenic
4 ppb (parts per billion)

Manganese, HR (Mn PP G)
negligible ppm

Magnesium (Mg G)
28.5 ppm

PH 7.9

I used a reducer on my shop vac and then taped a section of garden hose to it. It worked. Took a while to do, but got the job done.

In summary: On hard well water. Electric water heater. Water was not as hot as before and air bubbles were coming out of faucets. Pulled heating elements. Lower one buried in sediment and broken open. Also was not the same wattage as the top element as it should have been. Vacuumed out sediment, installed new element. Buttoned back up. Works once again. (Had to make a return trip to Ace Hardware because I originally got the wrong diameter thread on the replacement element.)