add DI or just get a new RODI?

[wowser]

I have a RO Pure system in my kitchen. Should I hook in a DI canister or just get a new RODI system? The TDS is about 10 right now. Considering a specturepure RODI system.

 

Which will be more economical in the long run?

 

It's this system:

 

http://www.amazon.com/Watts-Premier-RO-Pur...e/dp/B0035KLEFM

 

thanks!

[AZDesertRat]

Calculate your RO rejection rate using the tap water TDS and the RO TDS. The formula goes like this:

Tap TDS - RO TDS divided by Tap TDS x 100.

If we add numbers to that lets say the tap TDS is 250 and the RIO only is 10

250-10=240, 240/250=.96, .96x100=96 or 96% rejection rate.

 

96% would be a decent rejection or removal efficiency and DI would last a good amount of time.

A new 75, or in the case of Spectrapure 90 GPD RO membrane should be near 98% rejection or better. The higher the rejection rate the longer your DI resin will last and the better it will work. If the membrane is not performing well though DI would then act as a crutch to prop it up and could get expensive for resin replacements very quickly. A little known rule of thumb says for every 2% you increase the RO rejection rate or removal efficiency you DOUBLE the life of your DI resin. So, the difference between a 90% or even 95% rejection rate and 98% rejction rate can be dramatic in terms of DI life and cost of ownership.

 

Post your numbers here and I am sure myself and others can help you decide which route would be the most cost effective.

 

I will say, my first RO unit was a Watts Premier from Costco and it was a good drinking water system. I modified it for reef use by switching to a 75 GPD RO membrane, upgrading all the filters and adding DI and a TDS meter. I had much more invested by the time I was done than if I had bought a reef quality system to begin with. Of course this was many years ago too and the choices were not as many nor were they as affordable then either. Watts Premier is about a mile from my house here in Phoenix so I was able to do some horse trading with them for the membrane and some bench testing time which saved me some but not enough. You will also find with the type replacement filters your unit takes you will not find many of the more desirable micron ranges and carbon blocks reefers prefer. Standard 10" replacements are much cheaper and available in dozens of styles and micron ranges..

[wowser]

I would add a DI to the unit by putting a T to the spigot line adding a DI canister and then putting a small line with a valve for tank use.

 

I'll check my rejection rate and get back. Thanks!

 

 

 

Calculate your RO rejection rate using the tap water TDS and the RO TDS. The formula goes like this:

Tap TDS - RO TDS divided by Tap TDS x 100.

If we add numbers to that lets say the tap TDS is 250 and the RIO only is 10

250-10=240, 240/250=.96, .96x100=96 or 96% rejection rate.

 

96% would be a decent rejection or removal efficiency and DI would last a good amount of time.

A new 75, or in the case of Spectrapure 90 GPD RO membrane should be near 98% rejection or better. The higher the rejection rate the longer your DI resin will last and the better it will work. If the membrane is not performing well though DI would then act as a crutch to prop it up and could get expensive for resin replacements very quickly. A little known rule of thumb says for every 2% you increase the RO rejection rate or removal efficiency you DOUBLE the life of your DI resin. So, the difference between a 90% or even 95% rejection rate and 98% rejction rate can be dramatic in terms of DI life and cost of ownership.

 

Post your numbers here and I am sure myself and others can help you decide which route would be the most cost effective.

 

I will say, my first RO unit was a Watts Premier from Costco and it was a good drinking water system. I modified it for reef use by switching to a 75 GPD RO membrane, upgrading all the filters and adding DI and a TDS meter. I had much more invested by the time I was done than if I had bought a reef quality system to begin with. Of course this was many years ago too and the choices were not as many nor were they as affordable then either. Watts Premier is about a mile from my house here in Phoenix so I was able to do some horse trading with them for the membrane and some bench testing time which saved me some but not enough. You will also find with the type replacement filters your unit takes you will not find many of the more desirable micron ranges and carbon blocks reefers prefer. Standard 10" replacements are much cheaper and available in dozens of styles and micron ranges..

[wowser]

k, my rejection rate is 96%. Tap is 400ppm; RO is 15ppm.

[AZDesertRat]

That is probably acceptable. Did you test the RO TDS directly from the unit or did you take it out of the drinking water faucet which uses stored water? The reason I ask is water in the pressure tank will have higher TDS due to what is called TDS creep..

 

Install the tee leading to the DI directly off the RO membrane then place a check valve between the tee and pressure tank so you make DI directly from the membarne and not from the pressure tank, it will be slower but you will get better water quality and your DI will last much longer. Using a presure tank to make DI is not advised, same with storing DI water in a pressure tank since it picks up TDS. Also make sure you do not have a carbon taste and odor filter between the RO and DI as the carbon dust adds TDS.