If Ro/Di is working?

Read the earlier posts, upgrading or adding a DI was mentioned but is probably not a wise investment at this time.
The OP needs to get a handheld TDS meter and determine the rejection rate or removal efficiency of what he has before even considering adding on a DI. It could be money down the drain.
The handheld TDS meter is a much better investment than a inline as it gives you portability and is not dedicated to two testing points. To troublehoot a RO/DI you need a minimum of three TDS readings, tap water, RO only and RO/DI. With his RO only he could get away with a dual inline at this time but that leaves him lacking if he does upgrade to RO/DI as he will be missing that third TDS reading.

The OP also needs to get a better understanding of what he has today. it was described as RO/DI but only having 3 "stages". What is contained in each of those stages? How old are they? How long has it been out of use? Have they been allowed to dry out? What GPD is it? What brand and model is it? Has it been maintained regularly as in new filters every 6 months and disinfected to keep the membrane fresh? Lots of questions should be asked before taking on a used system and even more need to be answered before thinking about upgrading.

Bulk Reef is great with chemicals and stuff but would not be my choice for membranes or DI components, you can do better.

http://www.spectrapure.com/email/customer-appreciation.html#1

 

Agreed that he should get a better handle on the system he has, but as someone mentioned replacing the RO, and possibly adding on a DI, I gave him some affordable options so he knows what he's dealing with... Also, BRS has some good "how to's" and a visual reference may help him (it would help me if I was just starting out) understand his system better.

Can you please remark on why spectrapure RO/DI units are better than the BRS ones?

 

Regarding handheld vs. inline TDS meters, I have the inline meters that I referenced in my post. They will do the job of testing the water - before and after one or two canisters at least as good as we need them to.

Having a handheld unit is nice, but I like having my inline meters, so I can check TDS on the fly. I have mine installed before and after the DI cartridge. That way I know if the TDS is creeping up on the RO unit or after the DI, either of which would give me cause to service the system. I have installed it briefly before the RO unit, but the numbers I get there will only tell me what is coming from the tap supply... which can be helpful if you are calculating rejection percentage, but since I typically have 0-2 TDS coming from the RO unit, this is not that important to me. When my RO output rose to 10 TDS, I was still getting 0 TDS from the DI. I knew it was time to replace the RO because I could switch over the inline meter to read the input to the RO and quickly calculate the rejection percentage...

If you have a handheld unit, you will have to "break" the system and test the water individually which takes more time, and frankly is not something I want to be doing all the time. I see the inline meters as a convenient, easy way to check TDS quickly. If I had to spend more time doing it with a handheld unit, I'd probably skip the chore of checking the TDS every time I mix new saltwater. I'm lazy and like my tools to take the chore from the job. However, not checking TDS every time on at least the output of the RO and DI can be dangerous. It is this reason that I have never found the desire to have a handheld unit, but that is just me. I don't think that one is necessarily a "better" choice than the other... to me it is about saving time.

 

Spectrapure treats all their RO membranes with a special proprietary process to improve their eficiency and GPD rates. Then they bench test the membranes for quality control, with the normal membranes this is a spot check, with the Select series membranes they are 100% individually hand tested and then guaranteed in writing to be better than 98% rejection. This can be quite significant when you consider for every 2% you increase the membranes efficiency you DOUBLE the life of your DI resin. The average dry off the shelf RO membrane is around 97% once broken in so a 2% increase is a big cost saver.

They also custom blend every ounce of DI resin they sell based on thousands of hours of testing in their lab so you get the best reef quality resins available today. Its usually blended and vacuum sealed the day it is shipped so there is no fresher resin and the SilicaBuster normally outlasts comparable resin by about 30% so again a big cost saver.

Inline TDS meters are not as accurate as handhelds, they are not temperature compensated and actually sense air temperature which is rarely the same as water temperature so can be significantly off. They are fine for a quick indicator, I own two of the dual inlines myself but I depend on my handhelds for accuracy and repeatability.
Installing a tee and ball valve between stages is a good idea anyway and it not only gives you access to RO only water for drinking and other uses it gives you a test port. I have one after the RO only and one after each of my two DI stages so I can monitor each seperately.
The handheld also allows you to check your ATO water, tap water, the LFS water, your buddies water, bottled water etc. The inlines cannot do this.

 

I understand your points and you have justified the desire for a stand-alone meter...

Just one thing about temp compensation... This has never been an issue for me. The results that I get with the inline units have always been accurate enough for the purpose they are intended. I can't see any need for higher accuracy than what these offer.

For example, when I measure 45-50 TDS coming in from the tap, 40 TDS after the first two stages, then 1 TDS after the RO, and 0 TDS after the DI, I know all is working. If the number after the RO goes up, and the DI remains 0, then I know the RO is losing is effectiveness, but the DI is doing the job. If I get 1 TDS on the input of the DI and 1 TDS after the DI resin, then I know the DI cartridge is not working.

I typically don't want to spend a lot of time testing water, so the inline meters mean that I test EVERY time, and without fail. I would rather have this than a meter that offers just a little more flexibility, but that's me. I'll leave it up to someone to make up their own mind which is better for them, but I know which is better for me...

 

Remember the inline can be off about 2% for every degree C difference between the air temp and water temp so account for that when testing, 1 or 2 may not be 1 or 2.

If you have 40 or 50 TDS in your incoming tap water count youself very very fortunate, the national average is about 250 and mine is over 800.

 

well i got it from a guy who had it on a regular use. he said it was a coral life unit (which he purchased from a LFS) He recently replaced all the filters and said the membrane has 50% life left. I did order a TDS meter which i should be getting shortly and i will try to test the ro water from what i have, regular tap water and i will try to get someones ro/do's water to test as well.

 

Yes, I'm in Atlanta, and we are known for having very good tap water... in fact I was overestimating it a bit... I have measured it to be as low as 25-30 TDS on a good day... If you'd ever like to sample it, Sweetwater and Atlanta Brewing company both use tapwater as the source for their brews; after boiling out the chlorine, it goes untreated into their mash.

 

Alright, i got my Tds and here are the readings.

Tap: 164
RO: 49
5 stage Ro/Di water from safeway(grocery store): 7

Now what are the suggestions?

 

Well, your RO is running 70% rejection, which is horrible. I don't know why that is, but you absolutely need to get that down to the 1 to 5 range before you add a DI cartridge.