RO/DI - Phosphate Question

[rk4435]

My RO/DI water is showing .2 Phosphate straight from the filter. I replaced the four filters two to three months ago but did not replace the membrane because it is supposed to be good for five years.

I have a question about the way that I use the unit. It stays in a spare bedroom until I need to hook it up which is usually every Saturday and it runs until I get enough to fill up my Brute mixing can and ATO containers.

Since it sits for a week is that allowing the filters etc. to get nasty negating the whole point? If it is I may need to find a new source of RO/DI rather than replace the membrane. When I hook it up I always let it run for a while before I start collecting the water.

 

[jbdreefs]

How does your di resin look? Has it been replaced?

 

[rk4435]

I cannot tell a lie, I don't even know what DI Resin is. I'll have to look into that.

 

[ringo®]

It's the black carbon looking stuff in the last chamber.

 

[rk4435]

Gotcha, just talked to Air, Water & Ice. they clued me in on the DI resin cartridge. I was confused because BRS or someone sells a loose DI resin I believe. All cartridges were changed 2 to 3 months ago. They told me how to look at it and tell if it is still ok.

They told me that the way I am using it may be causing my problem. I have never fast flushed it, so the water sitting in the unit may be fouling the cartridges. Since I got it used I never knew any of the particulars of the unit aside from changing cartridges periodically. Hopefully I can get it sorted out tonight.

 

[reef insane]

Flush systems are included with some RO units these days. If you do a search on Google and look at images you will see some diagrams that show how it's plumbed. I hope this helps. I did this and it works great.

 

[rk4435]

I found a manual to perfor, the fast flush, nothing seems to make sense though. My TDS meter shows .000. When I did a PH4 test of the water I ran over the weekend it was close to .2 Phos. After doing the fast flush, the water from my RO/ DI unit shows .1 Phos, still way too high.

 

[seth the wine guy]

Most people have no idea how bad their RODI water is for PO4. TDS won't help you when it comes to PO4. This problem is one of the worst and most under publicized in the hobby and I can't understand why since we go to such lengths to remove it once detected in the tank.

Easy solution. I run a 5 stage RODI. (A four stage is fine too.) AFTER the five stages that INCLUDE a DI resin I run one canister of GFO then a second canister of DI resin after that. I would highly recommend anyone who's serious about their PO4 to consider such steps. Much cheaper and effective than trying to remove it after it hits your DT.

 

[rk4435]

I was thinking about trying to run GFO in my mixing bucket but I can't quiet figure that out logistically Seth.

I'm thinking my DI Resin filter looks bad despite being two to three months old. If it is bad then it comes down to the way I use the filter. I hook it up in my kitchen on the weekend and it sits in a plastic bin in the guest room until it is used again. Therefore, the water sitting is fouling the filters but there is no easy solution for that. I have no other way logistically to set the RO/DI up.

As it is I am getting so frustrated that I am about to have a 90 gallon Cichlid tank. The amount of work I put into the reef tank os staggering and it makes me feel like I work non stop, not to mention the money I'm spending.

 

[jennm]

Could your test kit be bad?

Just a thought.... TDS of 0 (or your TDS meter needs to be calibrated), shouldn't yield a phosphate reading...

Something doesn't add up.

Jenn

 

[seth the wine guy]

JennM;988544 wrote:

Just a thought.... TDS of 0 (or your TDS meter needs to be calibrated), shouldn't yield a phosphate reading..

Jenn

I beg to differ

 

[seth the wine guy]

I would venture to say any TDS meter being used by reefers measures accuracy to 1ppm. That means your RODI could be cranking out .95 PO4 and it wouldn't even show up on tds meter. I start freaking out if I'm over .15 PO4 with an acro tank.
Numbers like that should get people's attention and understanding of how little importance tds is to a successful acro tank.

 

[jennm]

Well there are several possibilities at play here. Accuracy of test kit as well as TDS meter.

BTW - an RO membrane's lifespan depends on many things, including the quality of the source water going through it, as well as how much it's used and how often, and what kind of maintenance is done on the unit. There's no cookie-cutter answer for how long a membrane will be good for, since the variables differ with each user.

Jenn

 

[rk4435]

Here is an update. AW&I talked me through troubleshooting the membrane. You remove the DI resin and run water then check the TDS. When I did that I had .004 TDS and they say that is acceptable for the membrane. Therefore they say that it must be my DI resin. I've ordered another and will check again.

They said that letting the unit sit for a week is no problem, but it must be fast flushed. I've never done that. After I did a fast flush the PO4 dropped a bit, but still too high at .1.

If the new DI resin doesn't fix the problem I don't know what will short of a new unit.

FWIW, the TDS meter is showing my tap water at .195 ppm. If I fill a glass with RO/DI is is .000. When I start slowly dripping tap water into the glass it climbs so I can only assume that the meter is measuring something and hopefully correctly.