Need some help from the RO DI experts

rocknut

rocknut

Rocky
I recently purchased a new RO DI unit in anticipation of getting my new tank all setup. After running it for the last week, I’m not 100% I have everything working correctly. The system using the following stages: First is a 1micron sediment filter, then it goes to a 1 micron carbon filter, then to the RO membrane, then to a color change DI, and a second inline DI stage, and finally to a 4 gallon storage tank before hitting an additional inline carbon filter. It seems that this should be a great system, and it was promised to provide water near 0 TDS. After a week of use, I haven’t seen a level less than 40 TDS, but usually around 50-60 TDS. My tap water measures 540 TDS, so that is only about a 90% reduction (the unit should provide anywhere from 97-99% reduction).
Honestly, this is my first RO DI unit, so even though I get the basic idea, I’m not to the point that I can narrow down what’s going on with this unit. The manufacturer insists that with the two DI filters I should be getting 0 TDS readings. I have rechecked all the hook ups, and connections 3-4 times, and can’t find any problems with that, and the unit does work correctly. When the storage tank fills up, the auto shut off works (I can hear the drain water stop as well.) The only piece of equipment that is not new is the storage tank that was from an old setup that was already in the house that I am renting. I removed the old RO unit, but decided to use the storage tank. In all probability this storage tank probably just sat under the sink for months, years (?) without really being used, or at least being used with filters that weren’t changed for years. Since the storage tank is past all filters except the final inline carbon filter, could this be contaminating the water after filtration? The other strange part is, the TDS readings fluctuate anywhere from 10-20 TDS each time I test them (by the way, my TDS meter is working fine, I have checked it on water I know has a TDS reading of 5).
Any suggestions?
 
I'd measure the TDS before the membrane, before both DI filters (individually), and after the last DI (before it goes into the tank). This may tell you what is and isn't working. Also, what pressure and temperature are you running through the membrane?
tom
 
Get yourself a squeaky clean drinking water glass with no water spots of soap residue. Next you need to test the tap water, triple rinse the meter and glass with DI, test the RO only before DI, triple rinse with DI again and finally test after the DI but before the pressure tank, take it out of the equation at this point.
These readings should give you your membrane efficiency and DI efficiency. Next test after the final taste and odor cartridge again before the pressure tank and finall test from the pressure tank. All this should identify the problem areas.
You need to scrap all that and get a Spectrapure MaxCap next time we do a group buy again, you won't regret it I guarantee you. I am getting an RO only TDS of 6.4 down from a tap of 795 and have been getting 0 TDS out of my DI for over 530 gallons now on the same cartridge! There are local group buys all the time.
 
This is a silly question, but: how do I remove the system from pressure? If I try to remove any of the lines for testing, I get hosed down with a high pressure stream of water. Is the pressure coming from the storage tank (by turning the valve on top of the storage tank off, will that drop the pressure?) Just out of curiousity, would it work to add a Spectrapure RO membrane to this system? This system (abundant water supply from Kansas) seems really well put together, so I can’t believe it’s just poorly put together.
 
Not knowing what membrane and filters they use its hard to tell the quality of the system. They may all look the same but I can tell you from experience they do not all perform the same by a longshot.
Yes you should be able to shut the pressure tank off and once you open the faucet the pressure should drop. Then you can unplug the various lines for testing between filters and components. I wish we had know you were buying a unit, we just got a smoking deal on MaxCap systems that couldn't be passed up! You can probably get group buy pricing on a SpectraSelect hand tested membrane but its only part of the system, without the absolute prefilter and 0.5 micron carbon block to precede it and the MaxCap/SilicaBuster following it you only have part of the equation and it takes all the components to make it really effective.
 
Well, worst case scenario, they do offer a 30 day money back on it (minus return shipping and restocking fee, etc...) Hopefully that's not the case. Thanks again for all the help, I'll let you know what I find out tonight!
 
...Since the storage tank is past all filters except the final inline carbon filter
Click to expand...

Im no expert but is it possible that this last carbon stage is adding some disolved solids?

wouldnt it make more sense to put the carbon before the ro and di units so they can remove any carbon products?

Again, I dont know much about RO systems, So if I am completly wrong, dont flame me. :)
 
The post carbon filter is for drinking water taste and odor. Its not needed nor wanted for DI water so its best to put it before the drinking water faucet. I run seperate lines for my uses so I store RO only water in the 14 gallon pressure tank and tee off from there. One lin goes into my kitchen through this post carbon filter and feeds my kitchen drinking water faucet and the ice maker. Another line goes to another RO faucet at my garage laundry sink and branches off to my MaxCap dual DI system for DI reef water.

And yes post carbon filters do add TDS. Thats why I instructed him to test each component seperately to see if thats what is causing his problems.
 
AZDesertRat,
I'm going to test everything tonight. I had no idea that the inline post carbon filter could actually add TDS. I'll let you know what I find out. Thanks again for all your help, everyone!
 
Unfortunately thats one of the things the drinking water people that try to pass their systems off as true reef quality RO/DI systems don't tell you. They also make claims that little throw away DI cartridges or little hollow horizontal tubes with some resin bobbing around in them work better than true 24 oz vertical canisters do. I have alwayssaid with RO/DI you really do get what you pay for. The component quality, filter quality, water quality and unit lifespan are very different among RO/DI units. The people on e-bay are making a killing selling unsuspecting people poor quality Chinese knockoffs and laughing all the way to the bank. Probably an overseas bank too!
 
I agree with you about the ebay thing AZDesertRat. After doing a lot of research about the one that I went with, it seemed to be a good choice. The filters are all standard sized, and are easily replaced with good quality filters. Anyway, I did what you suggested last night and got the following results:

Tap water = 571 TDS
Water from the RO = 96 TDS (I was starting to get worried...)
Water after the two DI stages = 0 TDS
Water after the inline carbon filter = 13 TDS (so you guys are correct, this is producing additional TDS readings.)

So, I guess it must be the old storage tank that was causing the high TDS readings. So now the question is: how do I go about cleaning the storage tank, or can I (does it need to be replaced?) Would it be a matter of running a bleach solution thru the system? I would just leave the tank off, but since I added the auto shut off valve that uses the tanks pressure to work, I'm not sure how to get around that (it will be a pain to crawl under the sink and turn the cold water supply on/off every time I want to use the unit.)
On a kind of side note, since the RO on this unit is fairly standard looking (one inlet, two outlets - one going to the drain, one suppling the processed water) would it be possible to just replace the RO membrane with a higher quality one down the road? Trust me, I bought one of those horrible Chinese RO units for $60.00 off EBay once, and this one really does seem to be a nice, decent unit, but maybe the RO membrane isn't quite up to snuff.
 
You may want to check your RO membrane. That is only about 83% rejection. Your DI's will be wearing out very fast.
 
Honestly I would think hard about returning it and getting your money back. A few things that really raise a red flag for me are
1. Nowhere on their site do I see what brand and model numbers of the membranes they use. This is disturbing. You need to know whet you are getting before buying it.
2. The membrane you chose is a 100 GPD which is some cases can be only 90% efficient on its very best day. Not good with any water but especially bad here in AZ with high TDS, DI resin is going to eat you alive in replacements. If buying anything other than a Spectrapure always specify a true Dow Filmtec 75 GPD 98% rejection rate RO membrane. Remember, for every 2% you increase the RO membrane efficiency you DOUBLE the DI resin life. If you are only getting 83% rejection with an incoming TDS of 571 your DI resin will need to be replaced every 32 gallons!!! Really not good! I have over 530 gallons on my first cartridge and its still going.
3. They tack a little throw away DI on top and call that a stage???

As for the bladder tank, yes a spoon full of bleach will disinfect it but it may also take straight vinegar to get any residual calcium out of it. Disconnect it and bleed the rubber bladder pressure off, put the bleach in the inlet nipple and fill it the rest of the way with
DI water and let it sit for a few minutes. For the vinegar fill it full and let it sit an hour or so and rinse with DI.
It may not be worth trying to save an old tank if its very dirty, they are pretty inexpensive.
 
I did get a few things resolved. First off, I did confirm that the membrane is in fact a Dow Filmtec membrane. One thing I didn't do last night while testing the RO water's TDS number, was let it run for a few minutes. I was testing the first drops of water coming out of the membrane as soon as I turned the water on. It is now my understanding that you should let it run for a few minutes first in order to get an accurate TDS reading? Does this sound correct. Also, I think I will just go ahead and replace the storage tank just to be safe, I have found a pretty good deal on one. I'll re-check the RO water tonight and see how the numbers look.
 
The 100 GPD Dow membrane is the worst possible membrane you could ever buy. Its not even an RO membrane and its not ANSI/NSF rated for drinking water in the USA. Its is in fact a nanofilter which is one step above a microfilter and one step below reverse osmosis. It is not rated for virus and bacteria removal like a RO filter is and if you look at the NSF site it is rated for "Pool and Spa Use" by the government. It will ony filter to 90% rejection rate at best and should never be considered for Arizona water, not even for drinking much less reef use. Most reputable vendors will do everything they can to talk you out of buying it since is just plain awful on a god day.
Yes always let the water run for a few minutes before testing to eliminate what is called TDS creep which is normal with all membranes. Spectrapure has a good explaination of salt creep on their sponsors forum.
If you decide to keep this unit at least return the membrane to the vendor and get a 75 GPD Dow Filmtec, not an Applied Membranes which is "constructed with materials from Dow Filmtec" or a GE Water either. It still bugs the heck out of me they don't proudly show brand names on their website. I find it odd, since brand names are a big selling point. Informed buyers want to know what parts and pieces are going into their unit. Also tell them to keep their throw away final DI and send you a true 24 oz vertical DI filter if they are claiming dual DI.
I hate to sound harsh but doggonit vendors like that shouldn't be around when all they are doing is taking your money and providing mediocre products.
 
I have an Ebay $99 Ro/Di

I have an Ebay $99 Ro/Di

I have the 6 stage Ro/Di filter with the 4 gal presser tank. I have had it since Dec 06. I just got a TDS meter today. My town water is reading 450. And my Ro/Di is reading 18 to 24. That is after, I'm guessing 700 gallon of water. ( I have a 50 G Brute Can) That I have filled 10 or 12 time, plus just normal drinking and ice water.
Last fall, my 125 tank got ammonia levels real bad(5ppm). Like it killed 3 of my fish, and for 2 weeks, the other fish were hiding. Till I got my level at least down to .25 (Ammonia). My reef tank has been set up for almost 4 years, with pretty good luck on the fish and mushrooms. But had to get a Ro/Di. I will probadly replace the filters with the better brands Later.
 
Make sure you replace the prefilter and carbons every 6 months to protect the RO membrane. Replace the DI cartridge or resin whenever you see anything other than 0 or no higher than 2 or 3 TDS. What happens is some contaminants are very weakly ionized so DI does not deal well with them even when it is brand new. When resin reaches its capacity it releases these contaminants back into the filtered water and at higher rates than it was originally, sometimes drastically high and all at once. A few of these weakly ionized substances are nitrates, silicates and phosphates all of which are bad for your reef. Don't put off regular maintenance or it will bite you big time.
 
Thanks

Thanks

Thanks AZDesertRat:
For all your knowlege on Ro systems and other stuff...You are what makes RC the greatest Saltwater sites around :D
 
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