R/O Unit Questions?

[Chuck S]

Okay I just got a ReefPure RO Unit and I have a few questions. On a RO Unit what is the pressure suppose to be? Mine is 42! Also what is a good TDS meter reading on the output of the flow. I get 3 PPM. I also want to know what the rejection rate is? Mine right now is about 25 good water 75 rejected bad water.

This seems like a lot of waste.

[Nanook]

Hey Chuck, I have a Spectrapure 5 stage unit that makes 35gpd. I don't know if this will help in your brand of purifier or not. According to my manual, the waste water ratio should be AT LEAST 4:1. The operating pressure for mine is 40-100 psi. My ideal operating PSI is 60, the manual has a correction factor table to figure out production rates with higher/lower pressures. Don't know if that helps with your unit, did they give you a detailed instruction manual for reference?

Dave

[Nanook]

Hmm, I just reread your post and saw that it was just an RO unit.

Dave

[tendar]

I have a fairly new Reef Aquariumsytems RO unit.
My presure messures aroud 42-45 like yours.
My TDS reading is around 40-45 ppm which I consider pretty good since my tap arizona tap water reads at 750 ppm.
I havnt really messured my rejection rate but it looks like about the same as yours 1:4 ratio.

[Chuck S]

No it is a 5 stage unit with one carbon block prefilter ro membrane and 2 di cartridges.

[Katspaw]

My Kent is about the same /ubbthreads/images/icons/smile.gif

Tracey

[RWD]

Chuck,
I have a Kent Marine but it should be similar. My instructions say that if the pressure is below 65 lbs the membrane will produce proportionately less water than its rating. Less than 40 psi and the membrane will act unpredictably. So I would say ro/di systems work best over 40 but preferably over 65 psi. I also find 4 to 1 waste to product water ratio about right. Don't know about the tds meter cause I don't use one.

[Chuck S]

Bob,

Yeah I am going to get the booster pump and that should help with push the water through the membrane and get things working right /ubbthreads/images/icons/smile.gif

[David Grigor]

About the best I can get from mine is a reading of 2-3 PPM on the TDS reading. When it goes it rises pretty quickly. I was told from AquaFx that when it gets to 30ish time to replace DI cartridge.

The one real interesting thing I found with the TDS meter is that I get another month or so use out of the DI cartridge after the resins have changed colors. Before the TDS I changed my cartridges too early......

[botp2k1]

Dave, I am not an expert but I would guess the DI be replaced when it is giving you a higher reading than just RO.

In other words, lets say I get 10 ppm out of RO only. I add a DI and end up with 0 ppm out of the DI. I keep using it this way and when the DI is exhausted, the TDS will climb. I would replace the DI when the output is higher than 10 ppm.

[Unresistible Blue]

The TDS in the product water from your RO is a function of the rejection rate on the RO membrane. These rejection rates vary significantly between manufacturers. Even within a single manufacturer of membranes, the rejection rate of their differnt gpd membranes may vary. Compare the TDS in your tap water to the TDS of your RO product water to calculate your rejection rate. Should be at least 90%, hopefully 95%.

[Mojoreef]

Chuck if you want to get the waste water down a bit, I would suggest what is called a permeate (sp?) pump. It is fairly cheap. What is does is to only allow the flushing water inot the RO when the RO/DI unit is running. It will also create an ammount of back pressure. I Have used it on my unit for a few years and it has knocked the waste water down to a 1 to 1 basis. I believe they only cost around 25 bucks and most places have it.


Mike

[Mash]

Chuck

3 ppm for your water is pritty good. I get 0 ppm but I am runing 3 chambers of DI resin after my RO unit.