Lots of scale -- is it the water or the heater?

DCContrarian

I have a heat pump water heater for the first time in my life. It's in a new house. It was installed about 18 months ago. About six months ago one of the heating elements burned out, when I drained the tank to replace it I noticed there was an unusual amount of scale in the drain water. I figured I'd better check back in six months. That was today. Attached are pictures of the element and what was in the drain water.




While I had the elements out I shined a flashlight through one hole and peeked in through the other. The dip tube and the anode both looked like stalactites, but the anode did not seem to be eroded.

My question is, is this just a symptom of what my water is like, or is there something about heat pumps? At this point I'm resigned to just flushing the tank every six months.

hot_rod

Usually the elements only scale if they are being used. The hot metal surface attracts the minerals in your water. Do you know if the elements are kicking on to boost production, often? Ideally you could run 100% in HP only mode.

The mineral precipitation will be directly related to the water hardness and TDS total dissolved solids

If you have hard water the options are a softener or a treatment like TAC.

I believe HPWH have a coil wrapped around the outside of the tank, so the scale will not be as much an issue as it is in gas fired type heaters, where it settles on the bottom and limits heat transfer.

No harm in flushing the tank occasionally.

Intplm.

It's not something about heat pump water heaters. Regular electric water heaters can have similar reactions to water, which is what your water heater is experiencing.

The rice stone/pebbles are common. I have had some water heaters with as much as two feet or more of those stones in an electric water heater.

Draining, or flushing twice a year might be unnecessary. You will know how often flushing is needed via. trial and error over time.
FYI:
Bradford White water heaters have a type of patented swirling action that can help prevent mineral build up at the bottom of the water heater.

DCContrarian

Intplm. said:

Bradford White water heaters have a type of patented swirling action that can help prevent mineral build up at the bottom of the water heater.

Isn't it better to have the build-up in the bottom of the water heater and flush it out once or twice a year than to have it flow into the piping and clog the fixtures?

EdTheHeaterMan

DCContrarian said:

Intplm. said:

Bradford White water heaters have a type of patented swirling action that can help prevent mineral build up at the bottom of the water heater.

Isn't it better to have the build-up in the bottom of the water heater and flush it out once or twice a year than to have it flow into the piping and clog the fixtures?

That will depend on the size of the particle that is being suspended in the water. Those pieces of scale in your photo are thousands of microscopic pieces of material that will join together to form a larger piece of scale. If you can get rid ir that stuff before it grows too big then you will not clog up fixtures. Then there is less scale to worry about.

And I believe that swirl is not in every water heater but is a function of the dip tube design.

Larry Weingarten

Hi, Looking at the scale, it tells two things. First is that the brownish stuff is hardness that fell from the element. It suggests that the heat pump isn't working very well, or that the tank is undersized for your usage. The bluish stuff is corrosion from an aluminum anode rod. It's a neurotoxin, so not good to ingest. I'd replace the anode with a magnesium one or a powered rod.

Yours, Larry

Derheatmeister

Are you on your own well or is your water supplied via municipal water/Treated ?

DCContrarian

Derheatmeister said:

Are you on your own well or is your water supplied via municipal water/Treated ?

City water, Washington, DC.

Derheatmeister

DCContrarian said:

Derheatmeister said:

Are you on your own well or is your water supplied via municipal water/Treated ?

City water, Washington, DC.

Can you obtain a water Quality report from your supplier ?

High TDS/Water hardness are probaly the source of your issues which can be addressed via localized watertreatment such as a water softener (Not a big fan) a Scale transformer or other Methods.
Since the Flint Michigan incidence some of the Municipal water suppliers have artificially brought the PH of the water up in order to prevent loosing the Patina from the inside of the piping system.
Patina such as copper Oxide(CU2O) is a protective layer that helps prevent Lead from leaching into our drinking water !
When teaching a Class in Denver regarding hydronic system fluid maintenance it became very obvious that the PH and TDS was very high when we sampled and tested the Domestic water supplied to the Building.
Also: In Talking to some of the trades we have also seen accelerated in increase in waterheaters failures which IMO is partially due to some of the things mentioned above.

ScaleIsMyEnemy

I have had this exact same problem with my new hybrid heat pump water heater. I contacted the city and was informed the water coming to my house was relatively soft, 61mg/liter. The manufacturer, AO Smith, installed a new special heating element that creates less sediment/scale that has definitely helped some. I also turned off the cold water mixer so that i could turn the temperature of the water in my heater down and it still get warm showers. None of this fixed the issue, but it is better. My question is, with me struggling to find this solution over 11 months, does that mean there is scale built up inside my copper hot water pipes? Do i need to do anything about that? …anyone have any permanent solutions for preventing the scale developing? It wasn’t an issue with the gas water heater I had before.

Larry Weingarten

Hi, Scale build-up happens largely with heat transfer, so there very likely is minimal build-up in your pipes, with such nice water. You do want a film of hardness inside of copper pipes as it's protective. Making sure the lines are insulated will slow heat transfer and help reduce any risk of scale build-up, but that applies more to very hard, hot water running through bare lines in very cold spaces.

Yours, Larry

hot_rod

Two numbers you need to look at. Softness, GPG or PPM number. Also the TDS total dissolved solids. You can have soft water, below 5 gpg for example and still have high TDS.

Within water there are positive and negative ions. Ion exchange softeners do not necessarily change the TDS and may actually increase it.

Only filtration like RO or DI can fix the high TDS. These remove both positive and negative ions from the water, TDS will drop after these type of treatments.

Some minerals in water come out of solution as you heat it. The ones on your elements and at the bottom of tanks. Other minerals go into solution when heated, think epson salt that we soaked swollen ankles in. But either of these ions can cause issues in boilers, HXers, pipes etc. So the DI water treatment for boilers removes all those potential problem ions.

Got an OHM meter? Volt meter? You can get some answers by measuring the conductivity. Or with disimilar metals, the voltage produced.

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Whatever water touches before it gets to you can be dissolved in it. The minerals in the water, slime in the pipes, any chemicals added by the water provider, etc. So a complete analysis will tell % of all these 1000's of possibility. Then the appropriate treatment needs to be applied. It can take multiple devices to get water where you want it.

Personally I would "fix" the water to be heated differently from my drinking water. I want the minerals, the good ones :) in my drinking water, but not in my water heater.

Oh, and another thing.. the water test you do today can be completely different weeks or months from now. Sources change, high run-off, temperature changes, etc.

So much to know about water.

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