High Tide Aquatics

BRS 7 stage ro/di question.

Srt4eric

Srt4eric

Vice President
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So it just came in the mail and I have it all set up and running now. After 45 min of running I'm showing 20 tds going into the first stage of di resin. The next two inline tds meters are reading zero. Wont that 20 tds going into the first resin stage eat up that resin pretty quick? Adding a second membrane to this would cut down on that tds going to the first stage? 60 psi coming out of the membrane would I need a booster pump for a second membrane or is that good enough? Should I just not worry about any of this since its 0 tds at the end?
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1. What is the TDS entering the membrane, or at least the TDS of your source water?
2. What is the advertised rejection rate of your membrane?
3. You don’t typically run the product water from one membrane into another, that would be pretty wasteful from an overall cost perspective. You run the waste water from one membrane into another to eek out a bit more product water for a given amount of prefilter/carbon block usage. This does often require a booster pump.

I would settle with being happy right now, but with the above info we can determine if this is expected behavior, or something being amiss.
 
jccaclimber said:
1. What is the TDS entering the membrane, or at least the TDS of your source water?
2. What is the advertised rejection rate of your membrane?
3. You don’t typically run the product water from one membrane into another, that would be pretty wasteful from an overall cost perspective. You run the waste water from one membrane into another to eek out a bit more product water for a given amount of prefilter/carbon block usage. This does often require a booster pump.

I would settle with being happy right now, but with the above info we can determine if this is expected behavior, or something being amiss.
Click to expand...


So my source water and the water going into the membrane is both right around 400.
I didnt even think of that. The 100gpd has a 96%-98% rejection rate as the 75gpd have a 99% rejection rate.
 
so from 400 to 20 that's a 95% rejection rate, that's pretty much in line with what you would expect, I wouldn't hold the labelled rejection rate as gospel though that typically is under "lab conditions" which could be 70° and 90 PSI or something (I forget the exact values they do it at).

Will it go through resin quickly, relative to someone with a 5 TDS? yeah you'll go through resin 4 times quicker, but it is what it is. The whole idea of the 3 resin canisters though is that you have a split of cation and anion resins each removes different stuff, so how fast it depletes largely depends on what that TDS is made of. Then the last resin is mixed bed to catch anything that slips by or when a resin chamber is running low. Just take a peek at it after every "water creation" session, it will be quite obvious when it's time to deplete (assuming you got the color changing stuff)
 
It sounds like your system is performing typically. As a friendly reminder as we enter cooler times of the year, RO membrane production corelates strongly to water temperature.
 
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