Why harden then soften?

[jjamison]

My system has first an acid neutralizing tank (calcite) next iron mitigation and then a water softener.
Does adding minerals then only to remove them make sense?
I try to understand the relationships between pH, KH, and GH as they pertain to aquariums, but in filtering my well water it seems the process is operating at cross purposes.
Is filtering with calcite and/or corosex then only to soften a common practice? and with reason?
thank you

 

[Reach4]

Calcite and maybe corosex is a fairly passive way to increase the pH of water. Yes, it adds calcium, which then adds to the load on the softener.

An alternative is to inject a metered solution of KOH ( potassium hydroxide/potash) or NaOH (sodium hydroxide/lye) into the water. That increases pH without increasing the calcium, but it has more that can go wrong.

 

[Sponsor]

 

[ditttohead]

Their can be many reasons for increasing the pH. It is a fairly complex topic but I will do my best to greatly simplify it.

Low pH may be a cause of damage to plumbing, fixtures, metal erosion etc. It is also difficult for many iron mitigation medias (primarily manganese dioxide ore) to be effective at low pH levels. A cheap way to raise the pH is running the water through a bed of calcite (calcium carbonate) and sometimes corosex (magnesium oxide). This inevitably raises the hardness so sometimes a softener may be desirable. If you already have 10+ grains of hardness then you are likely going to be adding a softener anyways so this makes sense. If your incoming water has very low hardness then some people will prefer to use pot ash or sodium hydroxide injection and then forgo the calcite, magnesium, and softener. Each application is different but in your application it sounds like a good design.

 

[jjamison]

Thanks for very much for your thoughtful replies Reach and Ditto!