Quick Question on RO/DI and filter/media selection.

[Rodney Butcher]

OK next question from the Newbie I just picked up a RO/DI system 6 stage used and I am going to replace all filters and media etc...

Previous owner has the 5 canisters setup as follows 3 sediment filters, 1 charcoal, and 1 DI.
My questions are : should I follow suit as is ,,,,,,or run dual DI and drop the charcoal ??
Next Question: As far as Gallons per day is that strictly based on the RO membrane that you purchase?
For Example if I assume I can dictate how much water production by the membrane I purchase ?
50 gpd or 75 gpd ??

Also does the higher GPD membranes do as good a job at removing stuff as the lower GPD ones ?

I do realize advertised GPD is a just a benchmark number based on water pressure temp etc... mileage will vary




As always Thanks so much in advance for your opinions, support and patience.

RB

 

[chipmunkofdoom2]

So to clarify, your system goes like this:

3 poly or sediment filters, one carbon block, one RO membrane, and one DI stage?

If that's the case, I would not run this setup. Three sediment filters is unnecessary. As are, in my opinion, more than 2 carbon blocks. I would do the following:

Low size sediment filter (1 micron or less), 1 - 5 micron carbon block, 1 micron carbon block, RO membrane, DI stage 1 and DI stage 2.

GPD is based on the membrane. Regardless of how much water you need, you should get the 75 GPD membrane. The reason is that the 75 GPD membrane by Dow has some great rejection rates (meaning it will give you very clean water and reduce the load on your DI resin).

As to whether you should change all the filters at once, unless you bought the unit second hand, I would not. You should replace the prefilters every 6 months on a schedule, or when testing indicates they can no longer remove chlorine/chloramine. Your DI resin should be replaced whenever your final TDS is above zero. Your RO membrane only needs to be replaced every few years, or when the rejection rate drops below 96%.

 

[Rodney Butcher]

BAM !! Perfect Thanks so much.

Side Note: I love this forum !!

 

[Rodney Butcher]

I did buy it second hand so I would like to start fresh on all of them. That way I know where I am at so to speak.

OK just to make sure here is what I plan on ordering and the order it needs to flow correct ?

• Stage one: GE ROSave.Z 1 Micron Depth Filter
• Stage two: BRS Universal 1 Micron Carbon Block
• Stage three: BRS Universal 1 Micron Carbon Block
• Stage four: DOW Filmtec 75 gpd Membrane
• Stage five: DI Resin cartridge
• Stage six: DI Resin cartridge

 

[chipmunkofdoom2]

OK just to make sure here is what I plan on ordering and the order it needs to flow correct ?

• Stage one: GE ROSave.Z 1 Micron Depth Filter
• Stage two: BRS Universal 1 Micron Carbon Block
• Stage three: BRS Universal 1 Micron Carbon Block
• Stage four: DOW Filmtec 75 gpd Membrane
• Stage five: DI Resin cartridge
• Stage six: DI Resin cartridge

That's how I would choose to do it, yes. Here is the reason why I chose each stage.

First, you want the sediment filter to be the first stage, and you want it to be small. The reason is that it protects the carbon blocks. If the sediment filter is larger than the carbon block, the sediment filter could allow larger particles to plug the carbon block and render it useless, even before it loses its ability to handle chlorine and chloramine. Keeping a small sediment filter, and hopefully one smaller than your first carbon block, will prevent your carbon blocks from failing before their time.

The two carbon blocks are all about handling chlorine and chloramine. Both of these are pretty hard on an RO membrane. Since the RO membrane lasts a long time if kept clean and protected, keeping the RO membrane well-protected is a good way to spend money in an RO system.

The RO membrane is pretty straightforward, it does most of the filtration in your system.

The two DI stages are to make sure you get the most out of your DI. As DI resin nears depletion, it can start releasing weakly-charged ions. With a single stage setup, you might have to toss the DI resin before it's fully depleted because it starts releasing weakly-charged ions early. If you run a dual stage setup, you can use the first cartridge fully and the water still has an entire cartridge of resin to go through. Once resin #1 is fully-depleted, you can swap resin #2 to position 1, put a new cartridge in position 2, and start the cycle all over again.

One thing to mention: when you replace your prefilters, you should unhook your RO membrane and send the flow from the prefilters straight down the drain for 10 minutes or so. New carbon blocks put off a lot of dust, and if you don't flush them first, all that dust will go right into your RO membrane and can ruin it pretty quickly. I actually have a tee and a valve between my prefilters and my RO membrane so I can flush when I install new filters.

 

[Rodney Butcher]

Once again perfect !! I was unsure of the purpose of the flush feature that I have been seeing on systems but now I understand its purpose sort of a membrane bypass when installing new filters.

Thanks so much !!

 

[chipmunkofdoom2]

Once again perfect !! I was unsure of the purpose of the flush feature that I have been seeing on systems but now I understand its purpose sort of a membrane bypass when installing new filters.

Thanks so much !!

You're welcome

To clarify, most RO units have a flush valve, sometimes like this one. But almost none come with the flush valve I'm describing. There's a line that goes from your prefilters to your RO membrane. This is where I recommend placing the valve. If you don't feel like buying a valve, you don't have to: you can simply unhook the line going to the RO membrane and put it down the drain for 10 minutes. But, at the very least, you should flush the prefilters whenever you change them.

 

[Rodney Butcher]

Yes my RO/DI has that type flush system on the Membrane cartridge combined with a 550 flow restrictor etc... I am adding a tee and a couple valves immediately after the sediment and carbon blocks along with a waste line back to drains so when I replace any or all of those first three I can divert water flow to pass through those first three for a few minutes and straight to waste. Thanks so much for a great tip that will no doubt proliing the life of my RO Membrane.

Also ordered complete refills for the entire system that way I can start fresh and know what I am starting with.

 

[dwest]

That's how I would choose to do it, yes. Here is the reason why I chose each stage.

First, you want the sediment filter to be the first stage, and you want it to be small. The reason is that it protects the carbon blocks. If the sediment filter is larger than the carbon block, the sediment filter could allow larger particles to plug the carbon block and render it useless, even before it loses its ability to handle chlorine and chloramine. Keeping a small sediment filter, and hopefully one smaller than your first carbon block, will prevent your carbon blocks from failing before their time.

The two carbon blocks are all about handling chlorine and chloramine. Both of these are pretty hard on an RO membrane. Since the RO membrane lasts a long time if kept clean and protected, keeping the RO membrane well-protected is a good way to spend money in an RO system.

The RO membrane is pretty straightforward, it does most of the filtration in your system.

The two DI stages are to make sure you get the most out of your DI. As DI resin nears depletion, it can start releasing weakly-charged ions. With a single stage setup, you might have to toss the DI resin before it's fully depleted because it starts releasing weakly-charged ions early. If you run a dual stage setup, you can use the first cartridge fully and the water still has an entire cartridge of resin to go through. Once resin #1 is fully-depleted, you can swap resin #2 to position 1, put a new cartridge in position 2, and start the cycle all over again.

One thing to mention: when you replace your prefilters, you should unhook your RO membrane and send the flow from the prefilters straight down the drain for 10 minutes or so. New carbon blocks put off a lot of dust, and if you don't flush them first, all that dust will go right into your RO membrane and can ruin it pretty quickly. I actually have a tee and a valve between my prefilters and my RO membrane so I can flush when I install new filters.

I’ll put in that tee before the membrane. Great idea!