RO/DI decision time

Yup that's 98% rejection. Just calculated to make sure. It could change but not too likely. That's a good rejection. Make sure you are running the unit for a while before testing the RO only (post membrane) and make sure the TDS is not still dropping. It takes mine about 5 minutes of free flow to finally reach a final tds.

The premeate will work fine with a pressurized storage tank and fridge/ice hook up. All you really need is the pump and if you want (optional), they make a high pressure ASOV. Do you have an ASOV yet? If not you will need one. The permeate pump works by using the pressure from the waste line to force water into the storage tank. Water in the storage tank will be pressurized so as this tank fills, the RO unit wastes more and more water trying to fight this back pressure. The permeate pump uses the waste water pressure to counter act the storage tank pressure. By doing this you will not see any increase in waste to good ratio even when you are filling up the pressurized tank. The pressure tank itself requires an auto shut off valve to turn your unit off when you are done. You will still want this valve if you use the permeate pump, but you will have the option of also getting a high pressure version of the ASOV. Do you know what your incoming pressure is? Also you can always add the permeate pump later if you like. You may want to see how you like running the unit for a while before installing it. The permeate was kind of a pain to install, but once in, it is zero maintenance at all.

I got mine from Buckeye and can help you with tips on installing it if you decide to go that route. I found the instructions a little confusing but I can give you all of the mistakes I made along the way.

FB
 
ok I just got my system, I have a handheld hanna tester and a duel inline. what do i want to test with the inline? I am thinking after the carbon blocks and after the RO?
 
That's fine. That's what I do. This will mean you will most likely use your handheld meter to test for DI resin depletion. The alternative is to have the inline come after the membrane and after the DI. This will make it a little harder to test rejection rates of the membrane but you can see when your membrane stabilized when you start making water and you can see that your DI resin is still producing zero TDS. Either method is fine and useful.
FB
 
ok, I got it all hooked up and flushed last night, I flushed tor 20 minutes instead of the 10 recommended. I think something ain't right. my TDS reading after the carbon is 650 and after the RO membrane it is 31
 
You may not be too far off. Thats a little over 95% rejection.
So. California like Arizona gets Colorado River water, us through the Central Arizona Project, you through the Metropolitan Water Dist. of So. California. Colorado river water is very hard and high in TDS, heck look at the Grand Canyon, where do you think all that dirt and rock went?:confused:
You membrane efficiency could be a little better. Have you checked it with both the handheld and inline meters? I don't always trust my inlines and always use the COM-100 handheld when I want accuracy. Here in Phoenix my tap averages 750- 835 or higher so 650 is not bad. My membrane is working better though as I get a RO only TDS of 5-6. Keep testing it and make sure your handheld tester and testing container are squeaky clean by doing multiple rinses in DI water between tests.
 
ok, I just thought the carbon should be knocking it down a bit more. I am still screwing around with it so, the water I am getting is "bursty" a pint or two at a time

handheld reads the di output at 0 TDS
 
Prefilters and carbon blocks have no effect on TDS, or very very little if any. They are there to trap TSS or Total Suspended Solids, or large particles microns in size and remove chlorine and some volatile organic chemicals. TDS or Total Dissolved Solids are much smaller, atomic molecular or sub micron in size and are the job of the membrane and DI.

You may need to take the unit in your hands and rotate it all around to release trapped air in the membrane housing or just let it go, it will eventually pass through in most cases.

Always disconnect or remove the DI during the first several gallons so you do not contaminate it with the initial high TDS water. Test the TDS from the RO with the handheld either through the RO bypass valve or with the DI cartridge removed.
 
how about all the air in the DI chamber? when it is running it was only about 1/3 full, but it seems the air would compress when it was shut off and fill about 3/4 of the way. I unscrewed the chambe a bit to let the air bleed out through the threads, does that sound right?
 
That is fine. It will not harm things if the air remains in the DI canisters but if you where able to bleed it out then that's also fine.
 
The air in the DI chamber is normal. The flow actually travels up through the center so what is on the outside between the cartridge and the canister does not matter.
 
well i did my first WC with my RO/DI water saturday night... all I can say is WOW! now I did change back to CL salt as well but my salt quest had started because I was not getting the kind of "POP" I was looking for in my tank. well, i can't say that things "POPPED" but by sunday morning, many were looking better than they had in a long time..

after testing my LFS @ 40+ppm, all I can and seing what my first WC did with my new water, all I can say is a good RO/DI is as esential as a CA, Mg, ALK test kit

thanks for all the help!
 
No problem. Great for you. Water is a pretty key ingredient to a reef tank so it's probably a good idea to start off with the best water possible. Glad you are enjoying your new unit and no more standing out in the rain.
 
thanks FB dux

one consern, I am getting 30 ppm tds from my membrane, 0 out of the di, I figure, i will be making not much more than 100 gal / month, how long should I expect my DI resin to last?
 
hmm, 30 ppm out of the membrane sounds quite high to me. What is the input tds? Are you rinsing off you tds meter with DI water and rinsing your container as well? Your unit does not have a post RO carbon filter for drinking water does it?
 
Hmm, that's only 94% rejection. You really should be getting better than that. And I assume you are waiting several minutes before testing the RO only water right?
 
My tap water TDS is 835 and i get an RO only TDS of 5 to 6 or a 99.23% average rejection rate even after almost two years of use. You can do much better than 94% and it will sure make your DI last longer. Mine went from 150 gallons per cartridge to over 630 gallons per cartridge once I invested in a better RO/DI system.
 
Yeah, that's odd. There are a couple possibilities we can try. I'll try to post more tonight when get off of work. But for starters, I think the minimum rejection listed for the DOW 75GPD is 96%. Perhaps DOW can send you a replacement if we can't get you up to at least 96%. Are you taking your post membrane recording from a pressurized storage container (might have more TDS creep)? Ideally, shut off any pressurized storage tank, and let the RO water flow for about 5 minutes or until it has completely stabilized before taking your measurement. Also make sure to rinse your meter and measuring glass in DI water. You should be getting higher than 94%. If that's as good as we get you, then maybe we can get your membrane replaced by DOW or buckeye.
 
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