RODI - TDS Readings

[catgirl29]

I bought a Spectrapure refurb 90 GPD RODI unit in May. I'm assuming all filters and membrane were redone during the refurb.

I've been seeing more algae despite water changes, cutting back on lighting schedule, etc. to no avail. I bought a TDS meter because I was starting to suspect my water. TDS is reading 46 which is about the same as my tap water - argh! I've purchased the three filters for the unit and they came in yesterday. Do I need to replace the membrane as well? I'll start paying more attention to this and replace out the filters more often? I have read that you usually don't need to replace the membrane(s) but once a year. I make no more than 20 gallons a week and sometimes less.

I have a booster I have not hooked up - I'll do that too. I read somewhere recently that low water pressure can lower effectiveness. I've always made water in a reasonable amount of time but I do think our water pressure is low and since this is a rental and an old house, I don't want to screw with that too much.

Opinions, experiences appreciated.

 

[black reef]

I bought the 5 stage rodi unit from brs and it came with the tds dual meter before the membrane and after di unit. Then I added one more prefilter stage ( dirt, metal trap ) before it enters the unit + upgrade to the 150gpd kit ( a second membrane ). So far they last so good for me over a year already. Still putting out 0 until now and iam running 3 tank ( 25cube, 175cube, and the newly setup 300dd). Before I used for water change I turn the tds meter on to check the water quality + using a handheld tds for those 5g container water storage before the mix with salt in the 32 brute trash can ( after I clean it up before mixing). That is my experience with the rodi. The tds meter will let u know when to change out filter + di.

 

[myreefclub0070]

Janelle,
there is several factors that play a part in when your pre filters and membrane's need to be changed, changing by date is based on the average user circumstances.
my filters last over a year by far and I run a lot of water through them.
here are the main issues that make the difference....
* water pressure.(min. 65 is good)
* in coming water quality
* de ironizing resin
* amount of or quality of pre filters to protect the membrane
* proper sizing of flow restrictor on the waste line
there is a few accessories that makes it easy to care for you rodi unit, like :
pressure gauge, input / output tds meter, dual membrane will double your water production, water meter and maybe a few others.

 

[snowmansnow]

If the output is 26 TDS something is wrong. It should be 0 coming out.

I'd make sure all your filters are seated properly and water isn't getting around them some way.

Again.. Your TDS should be close to if not 0


So long, and thanks for all the fish.

 

[snowmansnow]

Don't let setting up RODI be a big stress.... It's easy to do... You don't need all the add ons

All you need is Sediment filter - ro membrane - carbon block - di- and that will get you where u want to go


So long, and thanks for all the fish.

 

[catgirl29]

I haven't put in the new filters. With the old, I'm getting 46. Will change out the new filters tomorrow and test. I didn't get a new membrane but will do that if the other filters don't do the trick.

Thanks for the feedback, everyone. The algae issues are driving me crazy - I hope that this is one part of the fix. For six months, nothing - great tanks, then boom!

 

[snowmansnow]

Well one thing that can happen is you will exhaust your di resin if your membrane is bad. The di is just there to kind of polish it off.


So long, and thanks for all the fish.

 

[camellia]

Purchase the dual TDS meter. It will save you money in the long run by letting you know prior to killing your membrane as stated in post #2.

 

[jbdreefs]

What is the TDS of your tap water?

 

[black reef]

When u replace the filter + di resin, just don't hook up the resin yet. Take a reading before the water get to membrane,after the membrane, and see what comes out ( wait about after 5g of water before testing). That is the best way to make sure every stage work as it supposed to be ( numer of the reading should go down through each stage) if the reading after membrane is 5 or less , everything is working fine and u can connect the di stage to it and do one last reading ( it should be close to 0). I know it is a lot of work but trust me once u do all these, u will know how the unit works, how much it helps during each stage and how good your rodi water really is. One thing I recommend is using good / quality filter for it and it will last much longer (brs is the best in my opinion )

 

[jennm]

Something isn't working right if you have 46 on the output.

What's your untreated water's TDS? Mine here in Canton ranges between 38-42.

When you bought the refurbished unit, did the membrane come new in a package, and you had to install it? (Another thing to check is if the membrane is seated correctly in its housing.)

If you bought a unit and the membrane was already installed, there's no telling how old it was, if it dried out, etc. So if you got the unit with a membrane installed, you should just replace it. PM me - I can help you with that.

If your sediment filter is muddy, it's time to change it. Most folks use a 5-micron but if you have a lot of fine sediment, you should use a finer micron (like, 1 micron) and change the sediment cartridge more often. They are CHEAP (again, PM me...). Next is the carbon block. Make sure you get a good quality one, and pay attention to how many gallons it's rated for. They aren't all created equal. They are relatively cheap too - and keeping those 2 prefilters well maintained will prolong the life of your membrane, and then the DI.

Yes the flow restrictor must correspond to the membrane or that won't work right.

Low pressure will cause the unit to run for a longer time in order to produce the same amount of product water - all the while it is discarding waste water - so that costs in wasted water and a higher ratio. Ideally you should see 3 to 4 gallons of waste to one gallon of purified water. If it's higher than that, your pressure is too low.

Hook up that booster if you have it - it's worth every penny.

I suspect the problem is with the membrane for the high TDS you're getting.

Jenn