poll: RO before or after a water softener?

[clive1001blue]

would you install a RO before or after a water softener?

 

[Aquadude]

Definatly after a water softener. The softener will remove a lot of dissolved solids that can fould up the RO membrane. I don't know any reason why anyone would install RO before the softener.

 

[Len]

Actually, deionization is a kind of water softener too and it's normally used after the RO stage, so it's hard to say If your water is very hard, soften it first if you want to save the membrane life of your RO. I think there are situations for both.

 

[tangir1]

water softener only exchange the calcium with sodium. The amount of net ion on the water will be the same. Deionization is not really a bona fide "softener," but I guess you can abuse the term a little.

 

[kim]

As noted above, using a softener before the RO membrane can help preserve the latter.

After water has gone through the membrane, pretty much all of the hardness will be gone anyway, so there's no longer any point using the softener.

kim

 

[tangir1]

It is true that water softener utitily is very little if the input to it is RO'ed. However, having a water softener before the RO does make the membrane last long, but not very much. As mentioned, the TDS reading for water before and after the water softener is about the same (it exchange calcium with sodium, and the mobility of sodium is very close the calcium). Yes, water hardiness is a different measure than TDS.

 

[kim]

But calcium salts tend to be insoluble and can clog a filter. Sodium salts much nicer !

Of course, it's only noticeable if your water is nasty and hard (eg a lot of calcium and magnesium) in the first place, and also if you use the RO intermittently, so letting solids build up.

kim

 

[Minh Nguyen]

...However, having a water softener before the RO does make the membrane last long, but not very much. As mentioned, the TDS reading for water before and after the water softener is about the same (it exchange calcium with sodium, and the mobility of sodium is very close the calcium). Yes, water hardiness is a different measure than TDS.

The water here in Corpus Christi is very hard. My membrane without water solftener last 4 months with lots of waste water the last month. The Ca Co3 deposited on the membrane and ruin it by obstruct the pores and reder it useless. I have to instal a water solftener for my whole house and my membrane lasted for ever now (3 years so far with still the same out-put)
Minh