R.O. and Water Hardness

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Should an R.O. 4 stage filter (sediment/activated carbon/membrane/activated carbon) remove Carbonate Hardness (KH) and General Hardness (GH)? Or is it necessary to also soften the water with a resin ion exchange add-on?

Dave Kovensky
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[rscardigno]

Reverse Osmosis Membrane fouling

Most RO systems will reduce water hardness levels for your drinking water, but if your water is hard, it will decrease the life of your membrane significantly. The membrane will form a scale buildup that will reduce pressure and reduce water quality. Since water hardness is a problem throughout the home, it is best to install a water softener with a resin ion exchange for the home. This will remove any staining that you may be experiencing, soften your water throughout your home and protect your RO membrane which is the most expensive part in your reverse osmosis system.

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R.O. and Water Hardness

I do have an ion exchange water softener in my home. However, it brings the carbonate hardness down to 6 degrees dKH. Running this water through my R.O. unit does not further reduce this value. Only when I treat the water by a ion exchange water softener pillow, can I reduce the hardness to a lower value. My question is.....Is that a normal condition? i.e. Is an R.O. unit supposed to eliminate the carbonate (KH) and general (GH) hardness as well as remove the other contaminates?

Dave Kovensky
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[rscardigno]

Water Softener

RO systems are not typically used to reduce water hardness. They are typically used for drinking water only. Since water hardness has little effect on drinking water quality and more a concern with staining, water softeners for the whole house are used to control hardness. Have you had TDS test done on your water prior to the RO system and after the RO system? That would be an effective way to measure the effectiveness of the RO system.

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Water Softner

Please excuse my ignorance. Just what is a TDS test?

Dave K

[rscardigno]

TDS = Total Dissolved Solids

TDS stands for Total Dissolved Solids. Total Dissolved Solids is the total weight of all the dissolved solids which includes the salts, metals, and minerals in a given volume of water. The measurement will be given in parts per million or milligrams per liter. If your RO system is not removing 80% or more of your TDS then your RO membrane should be replaced. When was the last time your membrane was replaced?

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Water Softener

Thanks for your prompt answer on TDS. Incidentally, my interest in water conditioning is based on my hobby of raising and breeding tropical fish. I guess that the Hagen/Nutrafin definition of General Hardness (all the disolved salts) would comprise most of the Total Disolved Solids except for the metals. Anyway, I just ordered and received a 4 element R.O. unit and am in the process of assembling it. Once this is done, I can perform a TDS test of my water before and after it goes through the R.O. unit.

Perhaps you can help me out on another issue regarding Hardness Testing. In my Aquarium Pharmaceutical GH/KH testing kit, hardness is measured in parts per million (PPM). in my Hagen/Nutrafin GH/KH testing kit it is measured in miligrams per liter (mg/L). Are these measurements the same, or is there a conversion formula to equate one to the other?

Thanks again for your help in clarifying some of these water softening/conditioning problems.

Dave Kovensky
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[rscardigno]

1 mg/L = 1 PPM

The conversion is 1 to 1.

1 milligram per liter(mg/L) is the same as 1 part per million(PPM).