DI system only system questions

[Freenow54]

Between the carbon block and the RO membrane is a great place for bacteria to grow. No disinfectants, and plenty of nutrients in the tap water. The RO membrane mostly keeps bacteria out of the product effluent.

Hidden Dangers With Your Reverse Osmosis System

www.totalwaterllc.com

Recently we were at a customers house changing the filters in the Ro system. Their system was not producing much water and their membrane was not rejecting any TDS (total dissolved solids) which is the method of knowing whether or not your RO unit is producing purified water. Upon removing the canisters in which the sediment filter and pre-carbon filter were we found some serious slime build up. It was a gelatinous mass that had built up in the filters as well as within the RO manifold blocking the ability of the water to flow freely throughout the ports. The membrane had also been contaminated with this gelatinous mass. What was the gelatinous mass? Bacteria.

Amazing I thought light would be a necessary thing for that I guess not considering lets say a wound. Scary

 

[Freenow54]

That is why it is recommend to sanitize a drinking water RO system every 6 months of so.

After seeing the condition of my filters after 6 months filtering city water ( however is treated after it comes out of lake Erie ) I cannot bring myself to trust an RO system to drink. Now with Randy's input even less. I have seen and put more stock into a system that includes a UV in line light. So randy would that put where? Stop the bacterial growth?

 

[Syntax1235]

Yes sorry for taking over but I thought you wanted to save water as well which is why I mentioned what I use

No worries :-). I appreciate your comments.

 

[Freenow54]

Between the carbon block and the RO membrane is a great place for bacteria to grow. No disinfectants, and plenty of nutrients in the tap water. The RO membrane mostly keeps bacteria out of the product effluent.

Hidden Dangers With Your Reverse Osmosis System

www.totalwaterllc.com

Recently we were at a customers house changing the filters in the Ro system. Their system was not producing much water and their membrane was not rejecting any TDS (total dissolved solids) which is the method of knowing whether or not your RO unit is producing purified water. Upon removing the canisters in which the sediment filter and pre-carbon filter were we found some serious slime build up. It was a gelatinous mass that had built up in the filters as well as within the RO manifold blocking the ability of the water to flow freely throughout the ports. The membrane had also been contaminated with this gelatinous mass. What was the gelatinous mass? Bacteria.

Forgot to say it would even happen easier because of the single lever designs you could very easily be running hot for a while also people my self included rinse their mouth with warm. Have you watched the documentary on food poisoning? It started in the 60s with hamburg ended with the peanut king who knowingly killed 8 people and only got fined. The worst thing these days is bagged mixed salads apparently

 

[Randy Holmes-Farley]

After seeing the condition of my filters after 6 months filtering city water ( however is treated after it comes out of lake Erie ) I cannot bring myself to trust an RO system to drink. Now with Randy's input even less. I have seen and put more stock into a system that includes a UV in line light. So randy would that put where? Stop the bacterial growth?

I'd UV treat any water coming out of the system that might end up being drunk. Assuming you do not drink the di produced water, I'd put it on the line sending water into the hot water system, somewhere just before the hot water pipe junction.

 

[Syntax1235]

Update: The system has been working well until recently and I haven't had to recharge the DI resin, yet, I have the supplies to do so.

The first cartridge (cation) is about 50% depleted, and I have had to change out the two containers of anion once in the past couple of months. Everything seemed to be working well until the anion resin changes..... for some reason I'm getting a tds reading of about 12-25 out of the second anion stage. I am using the pro color changing anion resin from BRS. The final stage is a mixed resin that has been producing 0 tds until this recent anion change... now it is reading about 2 or 3 tds. I packed the resin well, tapping the canister to make sure there is no channeling.

To summarize my system:

1) Sediment filter
2) 5 micron carbon
3) 1 micron carbon
4) cation resin
5) anion resin
6) anion resin
7) mixed bed

Any ideas why I am getting a tds reading out of the anion stages?

 

[Randy Holmes-Farley]

Update: The system has been working well until recently and I haven't had to recharge the DI resin, yet, I have the supplies to do so.

The first cartridge (cation) is about 50% depleted, and I have had to change out the two containers of anion once in the past couple of months. Everything seemed to be working well until the anion resin changes..... for some reason I'm getting a tds reading of about 12-25 out of the second anion stage. I am using the pro color changing anion resin from BRS. The final stage is a mixed resin that has been producing 0 tds until this recent anion change... now it is reading about 2 or 3 tds. I packed the resin well, tapping the canister to make sure there is no channeling.

To summarize my system:

1) Sediment filter
2) 5 micron carbon
3) 1 micron carbon
4) cation resin
5) anion resin
6) anion resin
7) mixed bed

Any ideas why I am getting a tds reading out of the anion stages?

When you do separate di resins, the tds after the first one should always be higher than the tds going into it, no matter which one it is. That is because that resin either swaps all cations for H+, or all anions for OH-. H+ and OH- have higher conductivity than any other ions.

After both resins, the H+ and OH- combine to form water and tds drops.

 

[Syntax1235]

When you do separate di resins, the tds after the first one should always be higher than the tds going into it, no matter which one it is. That is because that resin either swaps all cations for H+, or all anions for OH-. H+ and OH- have higher conductivity than any other ions.

After both resins, the H+ and OH- combine to form water and tds drops.

Hi Randy,

That is exactly how I understand it, the tds after the initial cation phase is much higher than the water going into it from the carbon blocks… The problem is that the water after the following anion cartridges is still reading 12-25 and should be zero.

 

[Syntax1235]

Just to add a little closure to this thread for anyone who may find it useful, I think I have a hypothesis as to what is happening….

The cation resin depletes slower than the anion in my system, that is why I have two anion canisters. However, the cation is about 2/3 expired and I think that there isn’t enough contact time with that resin to remove everything that it would remove. When the resin enters the anion canisters it is unable to remove whatever the cation missed and is caught by my final mixed bed stage.

Apparently, there is two kinds of mixed bed resin, there’s the regular that includes an anion changing resin and a pro line that includes cation changing resin. I believe I had the regular mixedbed in my final chamber so I would not have seen the cation depletion.

The fix is to include another cation canister to increase contact time and to allow me to exhaust a full canister before refilling.

If I didn’t enjoy this so much, I’d really think that this is a real pain, but I really do like tinkering with all this stuff.

I’ll update in a few weeks and see if my assumptions are correct.

 

[KStatefan]

Just to add a little closure to this thread for anyone who may find it useful, I think I have a hypothesis as to what is happening….

The cation resin depletes slower than the anion in my system, that is why I have two anion canisters. However, the cation is about 2/3 expired and I think that there isn’t enough contact time with that resin to remove everything that it would remove. When the resin enters the anion canisters it is unable to remove whatever the cation missed and is caught by my final mixed bed stage.

Apparently, there is two kinds of mixed bed resin, there’s the regular that includes an anion changing resin and a pro line that includes cation changing resin. I believe I had the regular mixedbed in my final chamber so I would not have seen the cation depletion.

The fix is to include another cation canister to increase contact time and to allow me to exhaust a full canister before refilling.

If I didn’t enjoy this so much, I’d really think that this is a real pain, but I really do like tinkering with all this stuff.

I’ll update in a few weeks and see if my assumptions are correct.

That seems plausible. How fast are you running water thru your system? You also might benefit adding an adjustable needle valve to slow the flow down. That would increase contact time also.

 

[Syntax1235]

That seems plausible. How fast are you running water thru your system? You also might benefit adding an adjustable needle valve to slow the flow down. That would increase contact time also.

My tapwater psi is 51. By the time it reaches the first DI stage it drops to about 30. When my booster pump is running, I have the booster pump set at 65 psi after the carbon blocks and before the DI stages.

Even at the lower psi I don’t think the contact time was enough.

 

[KStatefan]

My tapwater psi is 51. By the time it reaches the first DI stage it drops to about 30. When my booster pump is running, I have the booster pump set at 65 psi after the carbon blocks and before the DI stages.

Even at the lower psi I don’t think the contact time was enough.

Flow not pressure a needle valve to reduce the flow. I also would not use a booster pump

 

[Syntax1235]

Flow not pressure a needle valve to reduce the flow. I also would not use a booster pump

What flow would you recommend?

 

[KStatefan]

What flow would you recommend?

I am not sure. Carbon filers that I use are rated at 1 gpm but the di might need less to get the contact time. I would consult with Russ @Buckeye Hydro

 

[Buckeye Hydro]

Max suggested flow through a 10" x 2.5" mixed bed DI cart is typically 0.25 gpm.

For reference, permeate flow at spec temperature and pressure from a 75 gpd membrane is 0.05 gpm.

No doubt there could be some experimenting with "your" particular water and various flows vs DI performance (measured via effluent TDS).

 

[charleydavis]

I should have researched this more thoroughly. I have a post by Randy that explained the raise in TDS... for anyone interested, here's his response to a similar question:

DI Cation Resin Low in / high out

Purchased new BRS resin for my 3 stage DI's. The Cation (#1) is adding 2TDs to the water. 1 in 3 out. This is something new. It did not do this on the last batch. Anyone else have this happen?

www.reef2reef.com

Randy's post:

"A cation binding releases one or two H+ (Rarely 3) for every cation bound. H+ is by far the most conductive ion, so TDS rises and the pH drops.
The anion resin releases one or two OH- (rarely 3) for every anion bound. Hydroxide also conduct very well so the TDS and pH rise.

Then when those fluids combine, the H + and OH- combine exactly to make nonconductive H2O."

It helps me to remeber that the resins are "exchange resins" meaning the cation resin exchanges H+ for other cations, such as Ca, Mg, Fe, Mn, and others. And similarly, the anion resin exchanges OH- for other anions such Cl, SO4, NO3, and HCO3. The total charge remains unchanged, but as stated above when H+ and OH- combine you have pure water. The resins will be depleted of their source of H+ and OH- at different rates.

 

[Randy Holmes-Farley]

Hi Randy,

That is exactly how I understand it, the tds after the initial cation phase is much higher than the water going into it from the carbon blocks… The problem is that the water after the following anion cartridges is still reading 12-25 and should be zero.

Ok, if the tds after both resins is not zero, either one (or both) is depleted, or water is channeling through one (or both).

 

[Randy Holmes-Farley]

It helps me to remeber that the resins are "exchange resins" meaning the cation resin exchanges H+ for other cations, such as Ca, Mg, Fe, Mn, and others. And similarly, the anion resin exchanges OH- for other anions such Cl, SO4, NO3, and HCO3. The total charge remains unchanged, but as stated above when H+ and OH- combine you have pure water. The resins will be depleted of their source of H+ and OH- at different rates.

FWIW, there is a fundamental charge balance in water where all the positive charges added together must match all the negative charges.

The problems arise from the very few chemicals in tap water that are uncharged passing though one resin but become charged inside the other depleting it. CO2 is one of those.

 

[Syntax1235]

Update:

I installed a second canister of cation DI resin and the tds dropped to 0 after the anion stage. The first cation stage being 2/3 expired did not allow enough contact time to do its job. I'll now be able to rotate canisters and will always have at least a full canister of cation and anion in the system. Success.... now I just need to periodically recharge the resin to keep things working as they should.

The system is now:

Tap water is 32 tds

1) Sediment
2) 5 micron carbon
3) 1 micron carbon
4) cation resin a
5) cation resin b
6) anion resin a
7) anion resin b (tds is reading 0 after this stage)
8) mixed bed

 

[Buckeye Hydro]

Update:

I installed a second canister of cation DI resin and the tds dropped to 0 after the anion stage. The first cation stage being 2/3 expired did not allow enough contact time to do its job. I'll now be able to rotate canisters and will always have at least a full canister of cation and anion in the system. Success.... now I just need to periodically recharge the resin to keep things working as they should.

The system is now:

Tap water is 32 tds

1) Sediment
2) 5 micron carbon
3) 1 micron carbon
4) cation resin a
5) cation resin b
6) anion resin a
7) anion resin b (tds is reading 0 after this stage)
8) mixed bed

What is the pore size on your sediment filter?

recommend you switch you carbon blocks - always put your highest capacity block first, right after the sediment