RODI help

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Sgc1107

Aquarium Advice Freak
Joined
Oct 19, 2012
Messages
406
Location
TN by way of NH
Buying my unit this week yay!! I was looking at buying it from purewaterclub.com what one is the best one there? Not quite sure what I'm looking at. Or maybe suggestions for another one?
 
I bought the cheapest portable one a few days ago, I am curious as well if these are good but for 65 dollars I'm not expecting a whole lot
 
Why would you buy the cheapest one for 65 and risk having some bad stuff in that water, another 65 bucks and u could have had the 4 stage system from bulk reef suply for 125.
 
I expected to pay around $150 maybe a bit more. Quality goes a long way in this hobby! I was looking at 5 or 6 stage is that the best you can go? I was also looking at RBS as there is a group but going on in a week or so!
 
Yes there is, i dont have an rodi system i use distilled from my grocer, 0 tds and 0 phosphates im happy payin 79cents a gallon.
 
Why would I risk? Because I'm cheap. I just won't use it if it tests poorly
 
I am curious as well if these are good...

I guess the primary factor in determining how good an RO/DI unit is, is the total dissolved solids (TDS) rejection rate of the RO membrane since the RO membrane is the 'work horse' of the unit.

A greater rejection rate will increase the longevity of the DI stage, which ideally should be be producing 0ppm TDS RO/DI water.

An ideal RO membrane should have a TDS rejection rate of 98-99+%. A less than ideal RO membrane may have rejection rate of less than 95%.

Every 2% increase in the rejection TDS rate doubles the longevity of the DI resin. The DI stage following a membrane with a 98% rejection rate lasts twice as long as the DI resin following an RO membrane with a 96% rejection rate and 4x's longer than one with a rejection rate of 94%.

The ultimate cost:
As an example, if the rejection rate of a "cheap" RO membrane is 90% (unit A), then the system is expending the DI resin 16x faster than a high quality membrane with a 98% rejection rate (unit B). The owner of unit A will have gone through 16 DI resin change outs by the time the owner of unit B replaces his DI resin for the first time. A cheap unit may be saving money on the front end but will be wasting money in DI resin replacement. (of course this is under the assumption that cheaper unit means less efficient RO membrane).

To determine the RO membrane rejection rate, substract the TDS of the RO water (not the RO/DI water) from the TDS of the tap water. Divide that figure by the TDS of the tap water and multiply by 100.

Example:
tap water TDS=225, RO water=12
225-12=213.
213/225=0.9466
.9466 X 100=rejection rate of 94.6%

rc_kaybee19_sig.png
 
I bought a cheap 4stage from purewater and it works great so long as it has the ro/ membrane and the di stage you should be good thefirst 2 stages are charcoal filters just don't run it horizontally
 
I guess the primary factor in determining how good an RO/DI unit is, is the total dissolved solids (TDS) rejection rate of the RO membrane since the RO membrane is the 'work horse' of the unit.

A greater rejection rate will increase the longevity of the DI stage, which ideally should be be producing 0ppm TDS RO/DI water.

An ideal RO membrane should have a TDS rejection rate of 98-99+%. A less than ideal RO membrane may have rejection rate of less than 95%.

Every 2% increase in the rejection TDS rate doubles the longevity of the DI resin. The DI stage following a membrane with a 98% rejection rate lasts twice as long as the DI resin following an RO membrane with a 96% rejection rate and 4x's longer than one with a rejection rate of 94%.

The ultimate cost:
As an example, if the rejection rate of a "cheap" RO membrane is 90% (unit A), then the system is expending the DI resin 16x faster than a high quality membrane with a 98% rejection rate (unit B). The owner of unit A will have gone through 16 DI resin change outs by the time the owner of unit B replaces his DI resin for the first time. A cheap unit may be saving money on the front end but will be wasting money in DI resin replacement. (of course this is under the assumption that cheaper unit means less efficient RO membrane).

To determine the RO membrane rejection rate, substract the TDS of the RO water (not the RO/DI water) from the TDS of the tap water. Divide that figure by the TDS of the tap water and multiply by 100.

Example:
tap water TDS=225, RO water=12
225-12=213.
213/225=0.9466
.9466 X 100=rejection rate of 94.6%

Holy smokes!! Great info! So should I be looking at stage 5 or 6?
 
When compared to the RD-102, based on the link the RD-106 comes with a 4gal pressure tank (and the photo displays one less DI resin stage, though the write up depicts two).

Optimally, (excluding the RO membrane housing) you'll want to go with all vertical housings to avoid any potential media by-pass (the DI stages in the watergeneral link have horizontal DI stages). The vertical housings also hold a greater resin capacity (visually it appears that one vertical DI housing holds more resin that two horizontal DI housings).

Just going by the ratings that are listed on their link I would go with a unit that has a RO membrane with a higher rejection rate. They list rejection rates of 95%-97%.

The BRS unit that dimdim referenced is equipped with a 75gpd Dow Filmtec membrane which offers a 98% rejection rating which out-performs the watergeneral units. (From what I understand, higher gpd results in lower rejection rates).

I personally use an Ultra-High Rejection Spectrapure membrane which rejection over 99% of the TDS from my tap water (tap water 259ppm, RO water 1ppm, RO/DI water 0ppm).

The water general dual DI stages will still provide 0ppm RO/DI water product water, however the lower rejection rates offered combined with lower resin capacity will result in a higher rate of DI resin expenditure.

For a unit approximately costing $150 I'd go with any of these three:

5-stage $160 RO/DI unit from TheFilterGuys:
RO/DI Systems

5-stage $159.99 RO/DI unit from BRS:
BRS 5 Stage RO/DI System - 75GPD - Bulk Reef Supply

5-stage $169.99 RO/DI unit from PurelyH2O:
http://purelyh2o.com/index.php?page...ategory_id=65&option=com_virtuemart&Itemid=64

(the Filter Guys & BRS 5 stage unit comes with 2 carbon blocks, while the Purely H2O 5 stage unit comes with 2 vertical DI stages). For water containing high chlorine or chloramine levels you may want to go with dual carbon blocks over dual DI stages.

Whatever unit you go with, for the most part they're interchangeable when it comes time to replace filters or membranes (if the housing are of the same horizontal/vertical orientation). Membrane change outs (if going from a 100gpd to a 75gpd as an example, may require a flow restrictor change out).
 
When compared to the RD-102, based on the link the RD-106 comes with a 4gal pressure tank (and the photo displays one less DI resin stage, though the write up depicts two).

Optimally, (excluding the RO membrane housing) you'll want to go with all vertical housings to avoid any potential media by-pass (the DI stages in the watergeneral link have horizontal DI stages). The vertical housings also hold a greater resin capacity (visually it appears that one vertical DI housing holds more resin that two horizontal DI housings).

Just going by the ratings that are listed on their link I would go with a unit that has a RO membrane with a higher rejection rate. They list rejection rates of 95%-97%.

The BRS unit that dimdim referenced is equipped with a 75gpd Dow Filmtec membrane which offers a 98% rejection rating which out-performs the watergeneral units. (From what I understand, higher gpd results in lower rejection rates).

I personally use an Ultra-High Rejection Spectrapure membrane which rejection over 99% of the TDS from my tap water (tap water 259ppm, RO water 1ppm, RO/DI water 0ppm).

The water general dual DI stages will still provide 0ppm RO/DI water product water, however the lower rejection rates offered combined with lower resin capacity will result in a higher rate of DI resin expenditure.

For a unit approximately costing $150 I'd go with any of these three:

5-stage $160 RO/DI unit from TheFilterGuys:
RO/DI Systems

5-stage $159.99 RO/DI unit from BRS:
BRS 5 Stage RO/DI System - 75GPD - Bulk Reef Supply

5-stage $169.99 RO/DI unit from PurelyH2O:
http://purelyh2o.com/index.php?page=shop.product_details&flypage=flypage.tpl&product_id=191&category_id=65&option=com_virtuemart&Itemid=64

(the Filter Guys & BRS 5 stage unit comes with 2 carbon blocks, while the Purely H2O 5 stage unit comes with 2 vertical DI stages). For water containing high chlorine or chloramine levels you may want to go with dual carbon blocks over dual DI stages.

Whatever unit you go with, for the most part they're interchangeable when it comes time to replace filters or membranes (if the housing are of the same horizontal/vertical orientation). Membrane change outs (if going from a 100gpd to a 75gpd as an example, may require a flow restrictor change out).

Wow your so helpful!! Thanks for the thought on chlorine too as I'm on city water with lots of it!!
 
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