RODI micron question

[ReefOcean]

I was looking at the Aqua Pure RODI units and decided to check some reviews. People seem to think they are OK but it seems unanimous that 5 micron sediment filters are like spaghetti strainers. I saw a few recomendations for BRS branded RODI which are only slightly more expensive (albeit you need to pay for shipping) but all of their packaged systems also come with 5 micron filters. So what is the deal? I would assume that BRS would include 0.5-1 micron filters in their packaged units if they were so necessary. Is 5 micron good enough?

[Myka]

Check out the "New to the Hobby" forum. I just posted an article about RO/DI systems a few days ago that talks about filter choices.

I like to match the microns of the sediment filter to the microns of the carbon filter. If you want to use 1 micron carbon filter then I would choose a 1 micron sediment filter. If the sediment filter clogs up too fast, then you can either a) deal with it because those filters are inexpensive, or b) add a second sediment filter so you can use a 5 micron ahead of the 1 micron. I do prefer to use 1 micron filters. 1 micron carbon filters are much more effective than 5 micron carbon filters.

[ReefOcean]

Originally Posted by Myka

Check out the "New to the Hobby" forum. I just posted an article about RO/DI systems a few days ago that talks about filter choices.

I like to match the microns of the sediment filter to the microns of the carbon filter. If you want to use 1 micron carbon filter then I would choose a 1 micron sediment filter. If the sediment filter clogs up too fast, then you can either a) deal with it because those filters are inexpensive, or b) add a second sediment filter so you can use a 5 micron ahead of the 1 micron. I do prefer to use 1 micron filters. 1 micron carbon filters are much more effective than 5 micron carbon filters.

Yeah I read that too, the carbon filter get's clogged and contaminated with stuff not caught by the prefilter. I would assume that yes, a 1 micron filter would be better since they can catch much smaller particles, thus creating a much more pure water. But in your opnion, is it really that much better? What sort of difference in TDS should one expect? What is the 1 micron filter catching that the 5 micron isn't?

Honestly I would just like to buy one of these cheaper systems and be done with it. But if having one of these units is the same as not having one at all, I would probably have to buy seperate filters etc and set up my own unit.

I will check out your article. Thanks.

[ReefOcean]

So I read your aticle and I am thinking I should just buy a package and replace one of the filters. Seems pretty easy.

[Myka]

Originally Posted by ReefOcean

So I read your aticle and I am thinking I should just buy a package and replace one of the filters. Seems pretty easy.

That's what I would do. You can buy a 1 micron sediment filter for $10 or less. How many microns is the carbon filter that it comes with?

[StirCrazy]

Watch what you buy and read the fine print, there are different ratings for filters, normaly you see 1 micron and it is an average size rating, this means there will be some bigger getting through also, what you want to look for is a 1 micron absolute rating, which means nothing bigger than one micron will get through.
Also, chloramins can be trickey and a normal carbon block filter is not enough, where two is. The dangerous part is the cl getting through and that is what kills your membranes.
When i buld a ro system from a area that uses them in the water system i put two carbon block filters befor the membrane which are both 1 micron absolute, befor that i put a 1 micron absolute sediment filter. Thoes are all standard 10x4 filters, on my own i went a step further and i bought a 10x6 housing and i use a graduated 25 to 1 micron filter in that as a prefilter. That alone has increased the life of my normal sediment filter and carbon blocks by about 4x.

I also do not use di filters anymore as unless you have realy bad water or your ro isn't working properly, your waisting money, if your tds is 0 befor your di, you dont need it so let it burn out then use the housing for a second carbon block. Other people will swear by them, i grew up in edmonton but i don't know the water there anymore so maybe you need it maybe you dont.

Things to keep in mind is you have two goals, to protect your ro membrane its self, and to produce the best water you can. A few years ago people were replacing membranes every year, we found this was from the switch from chlorine to chlorine/amonia mix, the amonia binds to the chlorine so it doesnt disapate in the water system and is harder to remove, which allows the citys to run lower chlorine levels and still have it last all the way to your kitchen tapat levels that provide proper protection. What we found was that one carbon block filter did remove a lot of it, but what it didn't remove was broke up into cl and amonia, bu adding the second carbon block you were insuring anything that made it through your first one was taken care of and when your first one started to be exhausted the second one also protected against that. The result for me was a extension to 5 years life on my ro membrane.
Steve

[Myka]

Originally Posted by StirCrazy

I also do not use di filters anymore as unless you have realy bad water or your ro isn't working properly, your waisting money, if your tds is 0 befor your di

Steve, ammonia from chloramine goes through the carbon and RO membrane untouched. The DI is what takes care of the ammonia. Also, a person would have to have very low TDS out of the tap to have 0 ppm TDS after just RO.

Most people run their RO membrane until the water coming out of it is 10-15 ppm TDS. The DI will polish that up, extending the useful life of the RO membrane.

Sent from my Dungeon using mad Ninja Skillz.

[StirCrazy]

Originally Posted by Myka

Steve, ammonia from chloramine goes through the carbon and RO membrane untouched. .

the Carbon breaks the bond and removes the CL, but the ammonia still carries on. the RO membrane its self will reduce ammonia to very low levels, depending on the PH of the water, design of the membrane and such, I supose if you still have residual ammonia you coudl use a DI, or other softener type ion-exchange. but to say the ammonia carries on throught the RO untouched is not right at all.

Steve

[Myka]

Originally Posted by StirCrazy

the Carbon breaks the bond and removes the CL, but the ammonia still carries on. the RO membrane its self will reduce ammonia to very low levels, depending on the PH of the water, design of the membrane and such, I supose if you still have residual ammonia you coudl use a DI, or other softener type ion-exchange. but to say the ammonia carries on throught the RO untouched is not right at all.

Steve

Sorry, I am mistaken. I was thinking about it more today, and my fish only systems bypass the reverse osmosis membranes. You are correct, the RO membrane will reduce ammonia based on pH coming out of the carbon filter.

[Myka]

I was just digging up some links for another thread, and came across Randy Holmes-Farley's comments on what passes through RO membranes:

"However, at the small end of the spectrum a number of compounds can pass through a reverse osmosis membrane to some extent and are, therefore, of concern to reef aquarists. These include carbon dioxide (CO2), ammonia (NH3), hydrogen sulfide (H2S, especially a concern with well water) and silicic acid (Si(OH)4, which is the uncharged and predominate form of silicate at pH values below 9.5). All of these should be trapped by a functioning DI resin (discussed below), but can still be a concern."

Obviously, there isn't a 100% fail rate with these compounds either though.