Iron Removal by Water Softener (low hardness)

[David Schmidt]

Hello, everyone.

My wife and I will be ready to move into our new home in a few months. The water analysis for our well shows the following concentrations:

TDS 610 ppm
Conductivity 970 uS/cm
Iron 1.67 ppm
Hardness 7.33 ppm as CaCO3 (0.43 gpg)
Calcium 2.22 ppm
Magnesium 0.432 ppm
Manganese 0.0135 ppm
Sodium 222 ppm
Sulfate 98 ppm
Chloride 8.6 ppm
Alkalinity 410 ppm as CaCO3
pH 8.65
Corrosivity -0.249 (Langelier Index)​

We will likely install a point-of-use RO unit under the kitchen sink for drinking & cooking. My question has to do with point-of-entry whole house treatment to reduce the iron level in order to protect our gas water boiler, other plumbing, and the RO unit.

The iron seems to be ferrous iron as the water is clear and colorless, and nothing precipitates out after the water sits for weeks (I’ve even aerated the water for a day with a fish tank aerator and no precipitation).

I understand that a cation exchange water softener would normally remove the iron, especially at our 1.67 ppm concentration. However, I’ve been told that because the water has so little hardness, softening may not work effectively. Here is the quote:

“Resin has a limit to the amount of iron loading it can handle. Under normal conditions its about 600 grains per cubic foot using 10 lbs of salt per cu ft. Most softeners are geared towards 6 or 8 lbs to be more efficient so it is more like 400-500 grains per cu ft. The rule of thumb formula is you need two grains per gallon (gpg) of hardness for every ppm of iron. (include manganese content with iron) This allows dispersion with the iron on the exhausted resin to make sure it is removed during regeneration. Too little hardness and the iron will eventually foul the resin and make it useless. 2 ppm of Fe/Mn needs to have a minimum of 4 gpg of hardness. I have always errored on the side of caution and like 2.5 gpg per ppm so I would want 5 gpg of hardness in this example.”

I’ve been unable to confirm this requirement for a 2-1 ratio of hardness-to-iron in order to prevent resin fouling in the softener. Can anyone confirm this information for me?

If this is true, it seems like our best option for iron removal would be a tank system using an oxidizing resin, possibly with air injection. Or perhaps a Pentek RFFE20-BB radial flow iron reduction filter. Any thoughts on these other options would be greatly appreciated.

Thank you very much!

 

[DIYMissus]

You don't need a water softener you need an iron remover. Using a softener only to remove iron is kind of like cooking a fish on a waffle iron.
Will it work ? Yes.
Is it the best method ? No.
Will you end up needing a new waffle iron sooner then you would have if you cooked waffles with it ? Probably

 

[Sponsor]

 

[WorthFlorida]

Try a little bleach in a bucket of water and wait and see. Bleach is an oxidizer and it may turn the clear water iron to rust.

A water softener is not an iron remover. Iron ion sticks to the resin and it slowly coats it impeding the sodium ion exchange for soft water. Unfortunately, many years ago marketing and sales decided that it can have an iron removal feature and too many have bought water softeners trying to remove iron. A product named "Iron Out" is used as a annual or more often a maintenance product to remove any build up of iron.
Salt pellets sold a s"system saver" has an iron remover chemical in with the salt to keep the iron at bay.

 

[ditttohead]

The radial flow iron reduction filters if they will work on your water... are extremely expensive and typically need constant replacement. Your high pH is beneficial to iron reduction but always be aware that even if everything looks great on paper, additional work may be needed. If you can find a local guy who is good at your specific water conditions then I would highly recommend using them. If you are determined to go the DIY routs, my recommendation would be something along the lines of aeration with katalox light, possible AIO with ozone, but as you are noticing, air bubbling is not working so maybe try the bleach as mentioned above. 1.7 ppm is not that much but it can make a mess of things in the house. You will likely only see a very small amount of precipitant in the glass. maybe us a 5 gallon white bucket with a small amount of bleach.

 

[David Schmidt]

Thanks for your helpful comments, DIYMissus, WorthFlorida and dittohead. From your responses, and additional research, I'm thinking that oxidation/filtration or an oxidizing filter media will be the best way to go. The house is being built in rural northern Colorado, but there are a couple of water treatment companies within about 90 minutes who I will interview; I might be able to maintain equipment, but I would want a professional to install.

I do have a follow-up question regarding waste disposal. Since the iron will be precipitated out whichever technology I use, I imagine the backwash water will contain some amount of iron solids. We have a new septic system (tank and leach field) and the design engineer warned against putting any water treatment waste into it. So my questions is, was he just being cautious or would oxidation/filtration or an oxidizing filter media produce enough solids to harm bacteria in a septic tank or form a "crust" in a leach field? What might my waste disposal options be?

 

[Skyjumper]

he was probably more concerned with dumping the extra water into the leach field. water is the enemy of septic fields. any solids should get trapped in the filter in your tank, or one of the baffles.

I would (and do) discharge the water treatment waste into a subsurface pipe that flows downhill and surfaces in the back corner of my property where it then soaks into the ground or continues to flow downhill. I don't know what kind of drainage situation you are dealing with, but i'd imagine your property slopes away from your house. find the low spot and dump it there. do you have a basement? a sump? you can discharge it into the sump and pump it out the low spot in your yard.

I say this not knowing what your local code allows. but even if it doesn't allow discharge of water treatment waste into your yard I would do it anyway after the inspectors finish their job and leave. dig a trench, bury a pipe, etc.