RO/DI filter change question

[solitude127]

Hello all. Recently, my RO/DI unit's in-line TDS meter read 15, so I decided to change out my sediment filter. I used a 0.5 micron sediment filter. My expectations was for the TDS to go back at least to single digits, but I was wrong. It only drop to 13. Did I do something wrong? Thanks

[jdieck]

Change the DI filter instead.

[ChuckLawson]

+1

The sediment filter takes out "big pieces" -- you want to change your DI resin.

[chaderic26]

+2

[918ReefCpl]

+3 - and be sure to follow the instructions to "wash up" the new cartridge before you use it to make water for your reef.

[AZDesertRat]

Prefilters and carbons have very little to absolutely nothing to do with final TDS. They are there to protect the RO membrane by screening out TSS or Total Suspended Solids, large particles and chlorine. The membrane and DI cartridge take out the TDS or Total Dissolved Solids, small stuff.

[solitude127]

Thanks everybody. So when my TDS goes up, should I only change out the DI filter or do all of them?

[AZDesertRat]

Change your prefilter and carbon block every 6 months like clockwork, these are what protects the expensive RO membrane. When you change them disinfect the housings at the same time to reduce or eliminate the risk of bacteria and virus growth in the filters.
Change the DI resin when you first start seeing signs of anything other than 0 TDS.
Change the RO membrane when you see a reduction in efficiency, if yours is a 75 GPD membrane you should be seeing a 96-98% reduction in TDS from the tap water reading with RO only. When it starts to go up after RO only that tells you the membrane is failing. 3 years is a normal life if you keep up with the filter replacements. 7-8 years or more is not unheard of, if you use premium filters like the 0.2 or 0.5 micron absolute rated prefilters and a 20,000 gallon carbon block.

[solitude127]

Originally posted by AZDesertRat
Change your prefilter and carbon block every 6 months like clockwork, these are what protects the expensive RO membrane. When you change them disinfect the housings at the same time to reduce or eliminate the risk of bacteria and virus growth in the filters.
Change the DI resin when you first start seeing signs of anything other than 0 TDS.
Change the RO membrane when you see a reduction in efficiency, if yours is a 75 GPD membrane you should be seeing a 96-98% reduction in TDS from the tap water reading with RO only. When it starts to go up after RO only that tells you the membrane is failing. 3 years is a normal life if you keep up with the filter replacements. 7-8 years or more is not unheard of, if you use premium filters like the 0.2 or 0.5 micron absolute rated prefilters and a 20,000 gallon carbon block.

Do I disinfect with bleech? Thanks for the info.

[Primetime33]

Yes.. good question.. What do we disinfect the housings with? I am getting ready to change mine out now but will wait now.

[Buckeye Hydro]

We recommend sanitizing your RO/DI system approximately once per year. Schedule this process at a time when you are planning to replace your cartridges. These instructions apply to water purification systems without a pressure tank. Before you begin assure that you have about an hour available, and that your work area and hands are clean.

Turn off the water supply to the system.

Remove all housings and remove all pre-filters and post-filters from the system including sediment filters, carbon filters, in-line filters, and deionization cartridges. Remove the reverse osmosis membrane(s).

Wash housings with a soft brush or cloth in warm soapy water. Rinse thoroughly to remove all soap. Don’t forget to carefully remove and wash all o-rings. Lubricate the o-rings with a small amount of silicone grease and reinstall them.

Fill each vertical housing with one cup of potable water and three to four tablespoons of household bleach, and with this sanitizing liquid still in the housings, screw them back on to the system.

Turn on the water supply a bit, allow water to fill the entire system, and assure water is flowing out of the waste line and the purified water line. Place the outlet of the drain tube and purified water tube slightly higher than the system to assure these tubes are full of the sanitizing solution. When the sanitizing solution has reached the outlet of each tube, and with the outlet of each tube placed above the rest of the system, shut off the water supply for 30 minutes.

After 30 minutes, turn the water supply on and assure that water exits the system from both the drain tube and the purified water port. Flush the sanitizing solution from the system for 5 to 10 minutes.

Turn off the water supply and install new filters, taking care to flush the filters as appropriate.

We recommend keeping a maintenance record for your system. Record the date of the sanitizing and filter replacement.

[Primetime33]

Wow!!! Thank you for the detailed reply/instructions. I am sure everyone appreciates it!!! I will be saving this information for sure.

[Buckeye Hydro]

You're welcome.

[solitude127]

Double WOW!!. Thanks a ton for all the info.

[jdieck]

Aren't you supposed to remove the membrane during the sanitizing? The bleach (chlorine) will kill it is not it?

[AZDesertRat]

Russ forgot to mention, either disconnect the 1/4" line from the carbon block where it connects to the RO membrane OR remove the membrane. For the 6 month disinfection I just disconnect the line and let it drain to a sink or bucket. This step is VERY IMPORTANT.
I prefer a little less bleach myself as it is very powerful stuff, up to 50,000 parts per million. All it takes is 0.5 to 1.0 parts per milion for successful disinfection. It does not take much, so I put 2 to 3 spoonfulls in the first housing only and let it circulate through the housings as I fill the unit. Bleach has a tendancy to adhere to plastic so a little goes a long way. And always use regular strength unscented bleach.

[Buckeye Hydro]

Yes - you bet. The 6th line indicates "remove the membrane."

[jdieck]

Originally posted by BuckeyeFS
Yes - you bet. The 6th line indicates "remove the membrane."

Thanks, somehow I missed it.

[AZDesertRat]

Guilty! I did too.

[solitude127]

How do I know if I need a Chloramine filter?

[AZDesertRat]

The best thing to do is check with your local water utility and ask them if they use chloramines as a residual disinfectant.
Most people do not need a special carbon even if chloramines are present. A good 20,000 gallon 0.5 micron chlorine guzzler type carbon block will do fine.
If you are served by the Metropolitan Water District they are converting all their plants to ozone, 2 or 3 are already done.
http://www.mwdh2o.com/mwdh2o/pages/n...ance/Ozone.pdf

[solitude127]

Originally posted by AZDesertRat
The best thing to do is check with your local water utility and ask them if they use chloramines as a residual disinfectant.
Most people do not need a special carbon even if chloramines are present. A good 20,000 gallon 0.5 micron chlorine guzzler type carbon block will do fine.
If you are served by the Metropolitan Water District they are converting all their plants to ozone, 2 or 3 are already done.
http://www.mwdh2o.com/mwdh2o/pages/n...ance/Ozone.pdf

Thanks again for all the info

[solitude127]

Another question. After I change my DI filter, what can expect the TDS to drop to?

[mhaith]

0

[grewbek]

Thanks BFS for the detailed info! I haven't read any of this before anywhere either and appreciate the detailed instructions. Mods, should this be a sticky somewhere?