Heat pump water heater and hard water

[less4success]

Does hard water change the calculus around heat pump water heaters?

I have hard water and had to replace the heating elements in my traditional water heater after < 4 years.

I assume a HPWH also would have a sacrificial anode rod, so maybe I’d just need to be more diligent about checking and replacing it (along with draining sediment periodically)?

Basically, everything plumbing related in my house gets overrun with iron deposits and sediment, so I’m not sure if I can count on enough time to pay back the cost of a HPWH.

I am factoring in a rebate from my utility. Not sure if the federal incentive will actually help me.

[uniwelder]

Posting to follow as we may get a heat pump water heater in the future.  My house has very hard water and tank is 7 years old, but we have installed a water softener 2 years ago.  When I inspected the anode rod 2 years ago, it was 90% intact.  From what I've looked up, heat pump water heaters have replaceable anode rods and internally seems to be the same as a conventional electric one, so I can't imagine making any difference in that regard, as well as regular maintenance like flushing out sediment.  The only thing I see that makes the heat pump water heater different is the heat pump sitting on top and refrigerant coils that wrap around the outside of the tank under the insulation.  I'm curious what other replies are received.

I'd recommend at least installing a whole house sediment filter.  For the sake of your washing machine and dishwasher, along with everything, else why not a softener as well?

[less4success]

Ah, I misunderstood the diagram I’d seen. If the only thing inside the tank is a backup heating element, then that’s much less concerning.

I don’t have a water softener because I have (old) steel plumbing, and I’m assuming adding sodium might cause rust, esp. when the pipes empty during various other plumbing projects (but that’s just a guess—I’ve never been able to find a definitive answer).

A sediment filter is a good idea. I’ll look into that.

[bacchi]

Yeah, the Rheem models (and the A.O. models, which I think are nearly the same) have a replaceable anode rod. Like a lot of water heaters, it comes out the top.

@uniwelder Why wouldn't the federal tax credits work for you? Not enough taxes due?

[less4success]

@uniwelder Why wouldn't the federal tax credits work for you? Not enough taxes due?

I think that was me. I just don't want to assume a federal incentive when it's possible we'll fall in between the two available incentives (too much income for the low-income rebate, and not enough tax owed for the credit--after taking into account other tax credits).

[uniwelder]

Ah, I misunderstood the diagram I’d seen. If the only thing inside the tank is a backup heating element, then that’s much less concerning.

I don’t have a water softener because I have (old) steel plumbing, and I’m assuming adding sodium might cause rust, esp. when the pipes empty during various other plumbing projects (but that’s just a guess—I’ve never been able to find a definitive answer).

A sediment filter is a good idea. I’ll look into that.

The diagrams I'm seeing show a coil wrapped around the outside of the steel tank.  The exception I think is Sanco, which is a much more expensive unit with CO2 as the refrigerant.  Since it wouldn't pose a health hazard should the coil leak, I suppose they can get away with putting it directly in the water tank for better heat transfer.

[bacchi]

@uniwelder Why wouldn't the federal tax credits work for you? Not enough taxes due?

I think that was me. I just don't want to assume a federal incentive when it's possible we'll fall in between the two available incentives (too much income for the low-income rebate, and not enough tax owed for the credit--after taking into account other tax credits).

Ah, right. We might be in the same boat for our mini-splits.

A Roth conversion would increase taxes owed and use up the credit.

[Sanitary Stache]

I wouldn’t expect a softener to alter the water corrosivity. Actually, I don’t expect it to. A softener will replace calcium and magnesium ions with sodium ions. The chloride anions should stay the same. Potential hydrogen won’t change and alkalinity should stay the same and I am pretty sure that those are the drivers of pipe corrosion.

The bottom of this article lays it out plainly. https://wqa.org/learn-about-water/perceptible-issues/corrosion/#:~:text=*Cation%20Exchange%20water%20softeners%20neither,is%20affected%20by%20water%20softeners.
The Water Qualtiy Association is the authority on home level treatment. I would only use an installer with WQA certification.

Your iron pipes are likely coated with calcium scale from your hard water. I am not sure if adding a softener will effect the existing scale. I’d like to believe it just will stop the increased build up of scale.

Softeners are installed with an adjustable bypass valve so you can dial in your preferred hardness. You don’t want completely soft water because minerals are good for you.

[less4success]

It’s the chlorine in salt that causes rust and not the sodium? How did I not know that until today!?

Not sure why I thought it was the sodium. That’s very encouraging!