when good RO water goes bad

[swims withthe fishes]

i tested my LFS RO/DI water for phosphate today and was shocked at my result. 1.0!! now i tested it with aquarium systems Fastest kit which is designed for SW, but tested it as FW. i then mixed 2 cups of sg1.024 (not easy) and tested again 2 times both readings @ 0.4
does the salt neutralize phos or is the test just innacurate without it?
does the RO/DI put phos in the water when the filters haven't been changed?
does RO/DI pull out phos if it's already in the water?
i hate to say it but i'm getting very close to not shopping at one of my fav LFS :(

[drtherc]

I would report the results of your test to the LFS. Maybe it's time for him to change his media.

[swims withthe fishes]

i plan to.. i'm just curious about those things for my own mental gain. it's very possible it's already in our nasty city water, but i don't know if it's just passing through the RODI, or is creating it. if it's just passing through it cause RODI don't stop it then it's not his fault. if he's selling water for .50 a gallon and being careless with his filters i'm gonna start shopping somewhere else. i'd ask him but... you know
anybody got a clue?

[jpfelix]

the di resin should take out the phos. however, as the resins fill they become less efficient. you may want to politely ask when they changed the di last. it may be that somone is supposed to but hasn't, or someone said they did more recently then they actually did.

[DaveC]

I believe I only get around 300 - 400 gallons tops out of my DI Resin in my RO/DI....it is the color changing resin, and it changes at around that amount....but I would guess a LFS selling Ro/DI water must go through alot....I 2nd the let him know suggestion...find out what he is using....if the canisters are clear and he is using the color changing resin you can not help but know when it is time to change......if his water continues to suck, go someplace else, or purchase yourself a RO/DI..will pay for itself over time.....

DaveC

[DaveJohnson]

Originally posted by swims withthe fishes
it's very possible it's already in our nasty city water, but i don't know if it's just passing through the RODI, or is creating it. if it's just passing through it cause RODI don't stop it then it's not his fault.
Oh yeah, it is his fault. If you don't have a TDS meter to check the water, ask him what the TDS is of the water he is selling. If it's other than 0 you're paying .50/gal for tap water (or close enough too it with that level of PO4)

PO4 should be 0 after you mix your water. 0.4 can be very detrimental to a number of corals, inhibiting calcification, plus IME hair algae thrives on PO4.

Cheers,
Dave Johnson

[JHardman]

I agree with Dave, whip out the ol TDS meter and it should always read 0ppm on RO/DI water. If it doesn't its time to change DI resin or RO membrane, carbon or prefilter or any combination of them.

It reminds me of a funny that happened to me last year...

A door to door salesman rings the door bell. I answer and he is selling "the purest water bottled water you can get". I ask is it really pure or do you leave things in the water or add things to the water for taste? He proceeds to tell me how they have the best filters in the business and that his water is 100% pure, completely filtered and nothing added. He has a nice bottle of water and some paper cups in his hands, so I ask him for a glass full. "Sure you will love the taste!". I ask him to come for second... get the old TDS meter out and take a reading of >500ppm. I ask to see the bottle while ignoring his questions of what that thing was I just stuck in the glass of water... I read the label, "bottled from city municipal water source from... (some city in Cali I have never heard of before). So I told him what the TDS meter was, what a reading of >500ppm meant, and pointed out the tap water source on the bottle label, and called the BBB and fraud division of the policy department. I also let all of my friends on the block know, going to each right before he got there. Boy was he mad. :lol: If he had not gone in to the whole "its the purest water there is, its 100% pure, completely filtered, best filters in the business" I would not have blinked and told him no thanks...