5 stage RO - 2 carbon 1 sediment?
 

Hi, we recently bought a home that came with a 5 stage RO hooked up to the fridge for drinking water and my attempt to research replacing filters lead me to a few forum threads here with great advice.

I've seen multiple references to "DI filter" and I don't know what that is and I suspect our unit does not have that. Two of the canisters are labelled "carbon" and one is "sediment" but the previous owners did one 5 micron sediment, one 1 micron sediment and one 0.5 micron carbon. Plus membrane plus odour removal carbon.

Is this incorrect and I should be using one sediment (1 or 5 micron then?) plus two 0.5 micron carbons?

There is no brand or model label that I've seen on the RO unit.

I've already read a thread that had advice on how to clean the canisters and watched a detailed video (where the guy had two carbon and one sediment) so once I have this answer I think I'll be OK. Any additional advice would be appreciated though.

Oh, is there a good way without a TDS meter, to guess if the membrane should be replaced? I don't want to replace it too early.

Thanks!

If it was connected to Fridge for drinking water, I am pretty sure that it doesn't come with DI unit. If you want to check if it DI or not. Look inside the canister. DI canister has a lot of blue / orange tiny balls.

This is how bulk reef supply and some of the other RO/DI system setup their 6 Stages unit.

6 Stages of Filtration:
Purtrex 5 Micron Depth Sediment Filter
BRS Chlorine & VOC 5 Micron Carbon Block Filter
BRS Universal 1 Micron Carbon Block Filter
75 GPD Dow Filmtec Membrane
Omnipure Inline Carbon Block
Pre-filled Single Deionization (DI) stage with refillable cartridge

I copied and pasted above info from BRS.

A drinking water system will not have DI (Deionization)
I run a 10 micron sediment followed by a 5 micron carbon, then a 1 micron sediment before the membrane. I run a dual DI afterward.

So 1 carbon and 2 sediments is fine? Is it carbon or sediment that takes out dissolved solvents?

thx

Try this website: h20guru.com they will have all of the info. also very willing to answer questions

From h20guru's site

Understanding the Reverse Osmosis Prefilters selection criteria.

The idea behind an array of filters is to provide for optimum pressure and a long filter life. The pre-filter micron rating required to optimize the life of a reverse osmosis membrane is five micron. No manufacturer asks for more protection than that and nothing is gained by smaller micron filters. In fact, you only hurt the overall performance of the system by using smaller micron filters. How do you hurt it? By causing excessive pressure drop.

Never install a one half (0.5) micron filter as a pre-filter. A filter array is designed so that each filter does the work required of it and protects the next filter in line. It would make no sense to dump big particles of dirt on a fine filter. You would clog it up immediately causing a great deal of pressure loss.

What I now recommend is: Get a ten micron sediment filter for your first stage, no smaller! Then obtain a good quality five micron carbon block, acid washed filter for the second stage. The ten micron filter has removed all of the dirt and sediment over ten microns from the water which protects the five micron filter. Now, all the five micron filter has to remove is sediment between 5 and 10 micron. In the third stage get a quality one micron carbon filter or a sediment filter if you have well water. You have now accomplished filtration down to one micron, five times the manufactures requirements. You have not lost a great deal of pressure and the filter can now provide you full service. So to recap; the ten protects the five, the five protects the one, and the one micron exceeds the requirement to protect the membrane by a factor of five, so your membrane sees only one micron sediment... one fifth the requirement.

Protected by a 10-to-1 micron array, the membrane is free to go about the task of removing bacteria, virus, salt, ions and dissolved metals (TDS). The filters alone have no impact on the TDS and should never be relied on to remove bacteria. Ions and bacteria are best left to the membrane. After the work done by the pre-filters and membrane, your water is very pure. The final stage is DI -- A typical mixed bed DI cartridge is capable of reducing the TDS to zero (0).

It kills me to see anyone recommend a one micron filter for the first stage!

The H2O Guru's at Air Water & Ice

Wow thank you!

Tap water quality varies greatly depending on where you live. There are certain minimum standards, but if not mistaken allowable TDS in tap water can be up to 500. Most water utilities will be well below that, but it's not uncommon to have a TDS of 200. The water in my area can vary from 60 to 200 depending on the time of year & source. We have two sources, one is lake water & one is from a creek fed elevated watershed. The lake water is harder than the creek source, hence higher TDS. The creek water has more sediment, but they spent a few million a few years ago to upgrade the filtration. Most of the time I'm on the higher TDS lake source, but the odd time they switch me to the creek source due to turbidity issues in the lake.

I guess where I'm going with this preamble is that the first step in determining how to best configure your water filtration system is to get all the info you can about your water source. Folks on the west coast in Vancouver BC, have very low TDS tap water, below 10 TDS most of the time. Clearly they can get away with a different sediment filter setup than I can with a TDS of 180 to 200 most of the time. Your water pressure & temperature will also impact the efficiency of your RO system. Yet another factor to consider is whether your tap water is treated with chlorine or chloramine. Chloramine is more difficult to break down & generally 2 carbon stages are recommended to protect the RO membrane. My system originally came with 1 sediment & 2 carbon stages before the RO membrane. After running for a year or so like that & doing some reading, I realized that I only needed one carbon stage since my city uses chlorine. My system currently looks like this:

5 micron sediment
1 micron sediment
0.5 micron carbon
75 gpd RO
DI

I bypass the DI for drinking water etc & only use DI for fish tank water changes & top off. This has worked very well for me, I'm still using the original RO membrane after years of use.

Depending on the quality & makeup of your tap water, you may need more or less filtration. It may kill the guru that anyone would recommend a 1 micron pre filter, but what does he know about your source water? You should be able to get an online report from your water utility. That would be a great start.

My RO system is dual purpose for drinking water and for making water for my tank. There is a give and take .....for drinking water a 5 or a 10 micron sediment MAY be fine... BUT THIS depends on your water quality. You should get a report from your water company. For fish tank.....I would say a 1 micron what most reefers use, possibly even .5 micron....once again depending on you water supply.

Another big consideration.....is your water supply treated with Chlorine or Chloramines. You should find this out. If it's Chloramnines....it's much harder to strip out than regular Chlorine. My water supply does use it.....hence I run the better Carbon filters at my 2nd and 3rd stage to handle the Chloramines. Chloramines will eat up your main membrane quicker thane Chlorine.

With my DI resin....I run a 3 way splitter to a separate dual DI Resin cartridge. When I am making tank water, I direct the water through the DI as the last stage before it hits my storage container. Drinking DI water is not good for you because it's stripped of everything.

Contact Russ at Buckeye Hydro. He is a vendor here and is very knowledgeable. He helped me with my system. Hope this helps.

I'd recommend you NOT follow this advice. This is advice originally developed by the previous owner of that company. Not sure about the technical background of the current owner, but I can't imagine recommending this sort of configuration.

In Phoenix we see TDS of 8-900!! LOL

Worked with a customer a while back with well water at 2400 ppm TDS. What a hoot!

I'm curious. Since its a drinking water system tied into the frig, is it standard size 10" cartridges?

Im on a private well also.
What would you recommend for my three pre filters, and why is the 10-5-1 configuration bad?
Thanks

The concept of smaller and smaller pore sizes on successive prefilters makes great sense, BUT it applies ONLY to sediment filters. Because you do not want your carbon blocks to trap sediment (you want them clean so they can do their job), your carbon block (s) pore size should be about equal to, OR LARGER THAN the smallest pore size on any of your sediment filters.

So, these are good:
10 mic sed->5 mic sed->5 mic carb
5 mic sed->1 mic sed->0.5 mic carb (carb is only 0.5 mic smaller than sediment pore size)

This is not good:
10 mic sed->5 mic carb->0.5 mic carb (you're forcing the carbon blocks to trap sediment smaller than 10 mic.)

Russ

assuming you do not have a chlorine injector system on your well, I'd start with 5 mic sediment->1 mic sediment->5 mic carb

Getting the correct sediment filter pore size may take a little trial and error - as everyone's sediment profile is different.

Well water often has high sediment loads - but not always.

Russ

And thank you Russ.

Thanks for the help, especially Buckey Hydro! Prev owners did 5mic sed -> 1mic sed -> 0.5mic carbon. So I suppose following that should work well. I'll try to find out how bad our chlorine or Chloramines are cuz then we should probably have 2 carbons. At least now I know the concept of not going lower than sed pore filter size. I wonder if 5 sed -> 1 mic sed -> 1mic carbon is better than 5->1->0.5

I still can't help but wonder if 0.5 is too small for the system. If 1 is 5 times better than manufacturer requires then maybe best to stay with that as the smallest pore size.

We've had good luck through the years with many systems using 1 mic sed and 0.5 mic carbon - it's a rare instance where there is enough sediment smaller than 1 mic but larger than 0.5 mic

Kay thx, I'm going to stick with the 5 sed -> 1 sed -> 0.5 carb for now. cheers

Is it ok to use Teflon tape, or whatever it is called, around the threads to prevent leaking? I don't have any leaking, just wondering if it's a good precaution or if that can contaminate the water at all.

If you're talking about the threads on the housing sumps, then no, don't use teflon tape here. The seal occurs at the oring, not at the threads. If your tighten the sump snugly by hand and the housing leaks, remove the oring, wash it, lube it, and re-install it. If it still leaks, replace the oring.

Russ

Yes you should use Teflon/plumbers tape on all the threads that connect pipework, actually in the instructions for my RO unit the manufacturer specifically tells you to do so to avoid leaks. The extract:

http://www.theaquariumsolution.com/f...ptfe_joint.jpg

Yes - on all NPT (tapered) threads. NPT threads seal by tapered male threads being screwed into tapered female threads. The seal happens at the threads.

No - on compression fittings or where seal occurs at an oring.

Russ