RO/DI Basic Guide

[Turbo's Aquatics]

The ratings are for removal, not clogging to the point that water won't go through it. I don't think you will get enough pressure buildup to balance it out.

I'm not sure I follow what you mean though. I'm sure the ratings for gallon capacity are based on a standard solution, and that the benchmark for whether or not the filter is "still good" is based on observed pressure drop. So if the pressure on the effluent side drops lower than a certain value, that's the "change filter" signal, and to me what that says is that the pores are clogged up enough that water can't pass through as easily.

So with that assumption (correct me if that is an improper interpretation) then if you have 2 identical filters in parallel (with a splitter before and a "combiner" or reverse-splitter after) then when cartridge A gets "clogged" more, the pressure drop across the other one (cartridge B) is less so you would get more flow through B, until it balances out. This would continue until the pressure drop across both was above the "change" threshold.

Again....I haven't ever seen this discussed and I don't know why. Am I missing a critical fact or something? Taking it to the extreme, one could put 10x 5 micron 15k Gallon blocks in parallel and that should be good for 150,000 gallons.

Now that I got your attention, how are them scrubbers coming along?

I'll be putting out an update soon

 

[Reefer1978]

I'm not sure I follow what you mean though. I'm sure the ratings for gallon capacity are based on a standard solution, and that the benchmark for whether or not the filter is "still good" is based on observed pressure drop. So if the pressure on the effluent side drops lower than a certain value, that's the "change filter" signal, and to me what that says is that the pores are clogged up enough that water can't pass through as easily.

I don't think that's exactly how the Carbon cartridges work. Pre-filter - sure, but not carbon. You can hear loose particles in a brand-new cartridge, so I don't see them getting clogged up enough to build any meaningful back-pressure.

 

[Woodyman]

@Woodyman question for you (instead of starting my own thread)

Can you see any reason why one would not run multiple identical carbon blocks or sediment blocks in parallel?

For instance, for a high volume system using a smattering of acquired equipment on a municipal chloramine system:

Stage 1: Pentek Chloramines Monster
Stage 2: dual 5 micron sediment in parallel (GE ROSave.)
Stage 3: single 1 micron sediment (GE ROSave.)
Stage 4: dual 5 micron carbon (BRS Chlorine & VOC)
Stage 5: single 1 micron carbon (BRS Universal)
Stage 6: split off to RO membranes...I have multiple systems, one dual 75s, one dual 100s, and a couple of single membranes as well

Stage 7: DI (consisting of cation, anion, and mixed bed individual stages)

All off a booster pump as well, with lots of TDS monitoring points, etc...would be able to isolate membranes for various levels of production

Mainly asking the question because...I can't find any information either way on it. Doesn't seem illogical to me though, for instance, the 5 micron carbon blocks are rated for 15000 gallons (of chlorine removal) and then the 1 micron is good for 35000 gallons. So logic says, put 2x 15000 in parallel and the water flow will balance out to the one with the lowest pressure differential until that one clogs up a bit, then it will shift over to the other one, etc...by the time I run 30000 gallons through it, I just replace all 3.

Or is there not enough consistency in production to count on this working this way (i.e. one will get all the flow, the other will get none)

Feedback below.

Now that there's some activity on this thread, can anyone answer my question?

Sorry I missed the notifications. I've got them turned back on now.

I'm not sure I follow what you mean though. I'm sure the ratings for gallon capacity are based on a standard solution, and that the benchmark for whether or not the filter is "still good" is based on observed pressure drop. So if the pressure on the effluent side drops lower than a certain value, that's the "change filter" signal, and to me what that says is that the pores are clogged up enough that water can't pass through as easily.

yes and no. Typically we don't worry about pressure being an indicator for carbon filter changes. Since you should pre-filter the carbon with a lower pore size filter, it should in theory never get clogged just lose capacity for removal of impurities.

So with that assumption (correct me if that is an improper interpretation) then if you have 2 identical filters in parallel (with a splitter before and a "combiner" or reverse-splitter after) then when cartridge A gets "clogged" more, the pressure drop across the other one (cartridge B) is less so you would get more flow through B, until it balances out. This would continue until the pressure drop across both was above the "change" threshold.

This would be correct, and there wouldn't necessarily be any harm in running carbon in parallel it also isn't typically performed because there is no added benefit in this application. Pressure for pore size/clogging can be ignored since it should be pre-filtered.

Again....I haven't ever seen this discussed and I don't know why. Am I missing a critical fact or something? Taking it to the extreme, one could put 10x 5 micron 15k Gallon blocks in parallel and that should be good for 150,000 gallons.

I don't think you see it discussed because for our application of RO/DI there isn't a practical benefit for the application.

The downside to this is that you risk chlorine/chloramine making it to your RO membrane. By running the carbon is series you can eliminate virtually all detectable levels of chlorine prior to the membrane. If you ran them parallel you would still be introducing trace levels of chlorine from both sides which could be introducing more chlorine vs a single housing (given both are identical). Granted even in that scenario it's not enough to worry about for our application/usage.

So while you can run them that way there are no discernable benefits that I would recommend that over in series. In series provides the most downstream protection for your membrane, which is typically the most expensive replacement filter for most users. Saving the membrane means saving you money.

 

[Turbo's Aquatics]

Thanks @Woodyman that's the answer I was looking for!

 

[Woodyman]

Thanks @Woodyman that's the answer I was looking for!

No problem!