RODI revamp and fine-tuning Questions

[Smoke-Town]

Ok so I've finally got my rodi out from under the kitchen sink and into a dedicated work space and I'd like to make it more efficient.

So I added a second tds meter from another rodi unit I had laying around. I now can see tds at source water, between carbon blocks and membranes, between membranes and di resin, and output water. I'd like to dial in an idea of about what I should expect after carbon, and after membranes. I know there is no one size fits all answer to this but maybe there are known percentages it should drop at each stage so I can have a better idea when to change my sediment filter and carbon blocks, and when my membranes start going downhill.

I'm on a well so that may make things a bit more difficult to dial in as my source water changes from between about 300-460 tds depending on rain and season.

My current levels:
Source: ~350
Post carbon: ~315
Post membrane: 11
Output: 0

So I'm only dropping 35 tds after sediment filter and 2 carbon blocks. Is that normal? They were replaced maybe in January or something. I forget, but I think a 5 micron sediment, 5 micron carbon, then 1 micron carbon. Either way I feel like it should be capturing more tds than 35.

My goal is to change out di resin less frequently so I feel if I can get better water to the membranes, I can get even better water to the di.

Also worth mentioning which I'm sure affects the membrane performance, my water pressure fluctuates between 40 and 50 psi. I'll be getting a booster pump for the house sooner or later which should hopefully negate the need for a dedicated rodi booster.

As an aside about pressure...I have the pressure gauge mounted before the splitter as I have 2 membranes. Also the line to the gauge is about 12" long. The back pressure would be the same from both membranes so I assume the gauge T location nor gauge line length would be an issue in accuracy right? Unfortunately my gauge is broken so I can't just test this myself yet.

Lastly, I have this 4 stage unit collecting dust.

I've seen the brs video where they use extra canisters to separate canionic and anionic resins and then the normal color changing mixed resin in the 3rd canister. Is that worth doing with this unit if I daisy chain it off my main unit and maybe use my current di canister for an additional carbon block?

 

[Smoke-Town]

Oh one more thing... I've been trying to flush for a minute every time I turn the rodi on. When I do... some water still makes it through the output line...it's certainly very restricted, but it does still come through... is this normal?

 

[Kazumi]

Carbon and sediment filters will remover very little dissolved solids. At 315tds in and 11 out, that is 96.5% rejection rate. If your pressure was up more that should increase your rejection rate. Separating the DI into individual canisters should make it last longer also.

 

[Kazumi]

I would take that spare RO unit you have, take the membrane off of it and replumb the canisters so you can have three stages of DI. Caton, Anion, and then a mixed bed one.

 

[Fish_Fry]

My company uses RODI water during our manufacturing process. I had issues with my setup and I spoke to our facilities manager about it. I was asked about when to change the sediment and carbon block filters.

His advice was to install a pressure meter between every stage. Then when the pressure drops you know the previous filter is getting clogged. He also recommends having a T valve before the RO membrane to be able to periodically test the water for chlorine / chloramines since they will destroy the RO membrane very quickly. He suggests using cheap swimming pool test strips.

He also suggests having flow meters at various points to keep track of water usage and efficiency. Some of his recommendations are definitely overkill, unless you use a lot of water.

I asked him about using separate canionic and anionic cartridges. He said that for industrial usages this is almost never done. The logic being it is easier to standardize a combined resin that works with all water sources rather than having dual solutions that are dependent upon outside variables such as the water supply. That said IMO if you know one would work better for your water type, than why not.

I haven't made these changes to my system yet, but I plan on doing incorporating a bunch of his suggestions within the next month or so.

Tom

 

[Smoke-Town]

Carbon and sediment filters will remover very little dissolved solids. At 315tds in and 11 out, that is 96.5% rejection rate. If your pressure was up more that should increase your rejection rate. Separating the DI into individual canisters should make it last longer also.

Ok. So if I do 3 Di canisters on spare unit, I'll have an extra canister on the current unit... should that be an additional sediment filter or an extra carbon block? And what micron would be best? If I'm currently running 1 sediment, followed by 2 carbons at 5,5,1 microns. So maybe one more carbon at .5 microns?

 

[Smoke-Town]

My company uses RODI water during our manufacturing process. I had issues with my setup and I spoke to our facilities manager about it. I was asked about when to change the sediment and carbon block filters.

His advice was to install a pressure meter between every stage. Then when the pressure drops you know the previous filter is getting clogged. He also recommends having a T valve before the RO membrane to be able to periodically test the water for chlorine / chloramines since they will destroy the RO membrane very quickly. He suggests using cheap swimming pool test strips.

He also suggests having flow meters at various points to keep track of water usage and efficiency. Some of his recommendations are definitely overkill, unless you use a lot of water.

I asked him about using separate canionic and anionic cartridges. He said that for industrial usages this is almost never done. The logic being it is easier to standardize a combined resin that works with all water sources rather than having dual solutions that are dependent upon outside variables such as the water supply. That said IMO if you know one would work better for your water type, than why not.

I haven't made these changes to my system yet, but I plan on doing incorporating a bunch of his suggestions within the next month or so.

Tom

Some interesting stuff here... pressure gauge at each stage... i like that... especially since gauges are cool and cheap... I think I'll do that. Definitely not doing flow meters, and I'm on a well so don't have chlorine to be concerned of.

 

[Fish_Fry]

I'll have an extra canister on the current unit... should that be an additional sediment filter or an extra carbon block? And what micron would be best? If I'm currently running 1 sediment, followed by 2 carbons at 5,5,1 microns. So maybe one more carbon at .5 microns?

Typically the larger filters are cheaper, so it makes sense to stack them in order. All the large particles get trapped first, so the small 0.5 or 1 micron filter can remove small particles without getting clogged with larger particles. Carbon works best when it is removing dissolved organics and not acting as a physical filter.

The decision should also be based on the quality of your water. My understanding is that well water typically has more sediment, or at least it can at various times during the year. For well water I would use 2 sediment and 2 carbon. My tap water is supposedly low in sediment. I'm more concerned with ensuring the carbon is optimized.

With 2 carbon the first one will reach the end of it's life, but the second one will still be effective. This should definitely help preserve your membrane. I don't have a specific size recommendations. Perhaps others can chime in. Personally I'm going to try a couple of different sizes and see what works best.

 

[Kazumi]

On my setup, I have whole house filters at 5 micron. The next time I change the RO filters I am planning on going to 1/2 micron sediment and carbon filters since most of the bigger things should be removed by then.

I would think that before you just add more stages of filters, you have your water tested to see what is actually in it. You might not actually need more stages.

 

[Smoke-Town]

Typically the larger filters are cheaper, so it makes sense to stack them in order. All the large particles get trapped first, so the small 0.5 or 1 micron filter can remove small particles without getting clogged with larger particles. Carbon works best when it is removing dissolved organics and not acting as a physical filter.

The decision should also be based on the quality of your water. My understanding is that well water typically has more sediment, or at least it can at various times during the year. For well water I would use 2 sediment and 2 carbon. My tap water is supposedly low in sediment. I'm more concerned with ensuring the carbon is optimized.

With 2 carbon the first one will reach the end of it's life, but the second one will still be effective. This should definitely help preserve your membrane. I don't have a specific size recommendations. Perhaps others can chime in. Personally I'm going to try a couple of different sizes and see what works best.

I'll check my sediment filter. I think that's fairly clean still. I have a culligan water system for the well to the house that I think does a good job for sediment. Also with a water softener salt filter.
I do wonder if the softener would be good or bad for the rodi. Doesn't seem to negatively affect it any more then when I was on city water a year ago

 

[KStatefan]

I'll check my sediment filter. I think that's fairly clean still. I have a culligan water system for the well to the house that I think does a good job for sediment. Also with a water softener salt filter.
I do wonder if the softener would be good or bad for the rodi. Doesn't seem to negatively affect it any more then when I was on city water a year ago

The water softener will remove items that are more likely to scale your membrane.

 

[Buckeye Hydro]

The water softener will remove items that are more likely to scale your membrane.

On commercial RO systems we install, where replacement RO membranes can be very very expensive, we nearly always also install a water softener before the RO.

Russ