Making Filters Last...

[Europhyllia]

This might be a dumb question but is there a way to make filter cartridges last longer.

I am sure my main problem is that I just use a lot of water.
I have a 215g tank and do weekly water changes of about 10% plus the usual top off for evaporation.

It seems like I am replacing the cartridges quite frequently. My DI resin also quickly changes color.
I have a 75 gpd unit.

Would a higher capacity unit help with the speed I am using up the filters? Or just make water more quickly with no effect on filter lifespan?

[ErikH]

A lower GPD membrane has a higher rejection rate. That will keep your DI from going out so quickly. I just bought the two extra DI canisters that run inline from the DI unit that is already on your unit. That way I dont have to change them so frequently.

[Europhyllia]

so I should stick with the 75gpd unit rather than upgrading to a 100gpd?

[Big_Pun]

i have a 150 gpd filter with just as high a rejection(98.5%) rate as a 75gpd

[BuckeyeHydro]

This might be a dumb question but is there a way to make filter cartridges last longer.

It seems like I am replacing the cartridges quite frequently. My DI resin also quickly changes color.
Would a higher capacity unit help with the speed I am using up the filters? Or just make water more quickly with no effect on filter lifespan?

So which filters are you burning through quickly? Just the DI?

One of the most common causes of going through DI resin quickly is that the RO membrane isn't doing it's job - and is delivering not-so-clean water to the DI.

I need a little more information:

What is your pressure at the membrane?
What is the TDS of your tap water? RO water? DI water?

Russ

[BuckeyeHydro]

A lower GPD membrane has a higher rejection rate. That will keep your DI from going out so quickly. I just bought the two extra DI canisters that run inline from the DI unit that is already on your unit. That way I dont have to change them so frequently.

50 gpd= 98%
75 gpd=98%
100 gpd=90%
150 gpd=98%

Russ

[Europhyllia]

interesting so avoid upgrading to a 100 gpd?

I just measured with the TDS meter

tap water: 82 ppm (seems odd - it used to be much higher!)

after RO on the RODI unit: 72 ppm

after DI on the RODI unit: 3 ppm

just as a comparison we have a RO unit for under the sink for drinking water and it comes out 12 ppm

This is the first time I disconnected the RODI and collected water straight from the filter thingies before it enters the DI cartridge

I don't think I have any pressure measuring equipment...

[BuckeyeHydro]

Karin - if your numbers are accurate, your membrane is toast, and so is your DI. My guess is the readings aren't accurate...

[Europhyllia]

do TDS meters go bad?
I even used new plastic cups so I don't contaminate anything...
I figured my DI was ready for a change again because it's all brown already (comes black) and I only installed it 2 months ago. I don't know how to single out which cartridge is bad so I just usually replace all the cartridges at once and the DI if it changed color and TDS goes up.
It's NOT one of your units.
I just figured if the answer was to upgrade to a higher capacity system I'd ask it here and then I could order one from you.

I just didn't expect all of the filters and DI to need replacing so frequently. If the membrane is bad did I do something to contribute to its demise or is this just something that wears out?

[BuckeyeHydro]

A good rule of thumb is to replace your sediment filter and carbon block after six months. A more precise way to maximize the useable life of these two filters is to use a pressure gauge to identify when pressure reaching the membrane starts to decline. This is your indication one or both of the filters is beginning to clog.

Also be cognizant of the chlorine capacity of the carbon block. A good 0.5 micron carbon block for example will remove 99% of chlorine from 20,000 gallons of tap water presented at 1 gpm. Some original equipment suppliers commonly provide carbon cartridges rated at 2,000 to 6,000 gallons.

Regarding your RO membrane and DI resin, use your TDS meter to measure, record, and track the TDS (expressed in parts per million) in three places:
1. Tap water
2. After the RO but before the DI
3. After the DI.

The TDS in your tap water will likely range from about 50 ppm to upwards of 1000 parts per million (ppm). Common readings are 100 to 400 ppm. So for sake of discussion, let's say your tap water reads 400 ppm. That means that for every million parts of water, you have 400 parts of dissolved solids. How do we go about getting that TDS reading down to somewhere near zero?

If you do some experimenting with your TDS meter, you'll note that your sediment filter and carbon block filter (collectively called “prefilters”) do very little to remove dissolved solids. So with your tap water at 400 ppm, you can measure the water at the “in” port on your RO housing and you'll see it is still approximately 400 ppm.

The RO membrane is really the workhorse of the system. It removes most of the TDS, some membranes to a greater extent than others. For instance, 100 gpd Filmtec membranes have a rejection rate of 90% (i.e., they reject 90% of the dissolved solids in feed water). So the purified water coming from your 100 gpd membrane would be about 40 ppm (a 90% reduction). Filmtec 75 gpd (and below) membranes produce less purified water (aka “permeate”), but have a higher rejection rate (96 to 98%). The life span of a RO membrane is dependent upon how much water you run through it, and how dirty the water is. Membranes can function well for a year, two years, or more. To test the membrane, measure the total dissolved solids (TDS) in the water coming in to the membrane, and in the purified water (permeate) produced by the membrane. Compare that to the membrane’s advertised rejection rate, and to the same reading you recorded when the membrane was new. Membranes also commonly produce less water as their function declines.

After the RO membrane, water will flow to your DI housing. DI resin in good condition will reduce the 40 ppm water down to 0 or 1 ppm. When the DI output starts creeping up from 0 or 1 ppm, you know that your resin needs to be replaced. Sometimes people complain that their DI resin didn't last very long. Often the culprit is a malfunctioning RO membrane sending the DI resin “dirty” water. This will exhaust the resin quicker than would otherwise have been the case. Sometimes the problem is poor quality resin – remember that all resins are not created equal!

Russ

[BSJF]

I vote for an upgrade Karin. I love my Buckeye unit!

[Europhyllia]

Oh wait I think I unplugged the thing at the wrong spot to measure for RO. I think I measured before it goes through the membrane
so adjusted for ignorance my values are currently:

tap water: 84 ppm

after RO filter blocks on the RODI unit: 72 ppm

after RO membrane: 28 ppm

after DI on the RODI unit: 1 ppm (according to this morning's test)

I am ordering a pressure gauge kit to see what units would even work on my water line according to psi and can figure out what my options are from there. Thanks for all the good info!

[BuckeyeHydro]

OK - even with those numbers, assuming their accurate, you still have an uissue with your RO membrane. With your tap water at 84 ppm, your RO water should be 8 or less - even down below 5 ppm.

With the high TDS in your RO water you are going to burn through DI resin quickly.

Russ

[Europhyllia]

okay well that's sort of good news I guess. I have hopes that perhaps I don't need to replace all the filters every 7 weeks then once I either get a new membrane or a new unit.
I already ordered the pressure gauge thingy from your website this morning.
If my water pressure looks right for the premium 150 gpd unit then that might be the one I want.
Is it possible to upgrade from handheld TDS to dual inline with this package? I already have the HM TDS handheld and really like the push a button digital monitoring devices

[BuckeyeHydro]

You bet!

[txmike]

i have the 150 gpd with dual in line tds been running for 6 months now still putting out 0 TDS 2 to 3 out of the RO and 0 out the DI i make 40 to 50 gal per week.Love the system.

[Europhyllia]

one more question:
I think right now I have a 5 stage unit and looking at the Premium 150 gpd unit it appears to be 4 stage.
I tried to compare my filters and it appears the extra stage I have is a 6 mic carbon block. Is that (likely) correct?

I assume most people do fine with a 4 stage unit then without the extra filter (looks like the refills cost less that way too)

[txmike]

4 stage is sediment ,carbon,ro,di .I run my system after a hole house filter of 5 mic and after my water softener http://i736.photobucket.com/albums/xx7/txmike2/rodi.jpg

[Europhyllia]

Oh Mike you are right! Looks like the extra stage I have on my old unit is a 6 micron carbon block.

[BuckeyeHydro]

4 stages is the place to start (and for most people, the place to end too!) with these systems. With most tap water, there's no need for additional stages. If you have heavy sediment loads, or chloramines, or any number of other uncommon water quality issues, THEN is the time to think about adding stages. For most water supplies, a sediment filter -> carbon block -> ro -> di is all you'll need.

The most popular pore size going is a 1 mic sediment filter teamed with a 0.5 mic carbon block. Again, this is a great, top-shelf combo for most people, in most situations.

Russ

[ramsey]

Sorry for reviving a dead thread but isn't changing the filters because your TDS is 1ppm excessive? I thought anything under 10 TDS is still good. I obviously understand that 0 is better but If I can get a few more months out of my cartridges with no harm to my tank, why should I change them? Just curious.

On a side note, alexdmg has one of your units and it's awesome. I may plumb one into a line in my house and run it into my top off container. I'll look you guys up if I decide to.

[BuckeyeHydro]

Hi Ramsey. Once the output from the DI resin comes up off of 0 or 1, it is dumping materials you used it to capture.

Russ

[ramsey]

So what you're saying is that anything over 0 or 1 and the DI part is not effective? I'm basically just asking what an acceptable TDS is. Mine is 3ppm right now. I read on melevsreef.com that anything under 10ppm is acceptable. That dude has a pretty nice tank too. :)

[BuckeyeHydro]

As long as the DI water TDS is lower than the RO water TDS, you know it is capturing ions. But as the DI TDS starts to climb, the DI is also dumping certain ions in favor of other ions.

I can't give you a precise number, because we don't know what the ions are in the DI water, but the first to be released by the di are monovalent ions (e.g., ammonia, silicate, nitrate). So unlike tap water at 3 TDS, which would likely be just fine to use, the dissolved solids in 3 TDS DI water are likely not what you'd want in your tank.

I suspect there's no data to support the claim that 10 ppm TDS DI water is ok, other than as you noted, that's what he does and with his particular tap water, his corals, his refugium, etc, etc, it has worked out.

If the issue is that you want your filters to last longer, I'd think about a few other things than leaving the DI resin in longer. For instance:
1. What is the TDS of my RO water?
2. Is my pressure too low?
3. Do I have high CO2 in my tap water eating up my DI resin capacity?

And don't forget that the prefilters (the filter stages that come before the membrane in order of water flow) don't remove dissolved solids. So it may be that your prefilters can stay in longer but just your DI needs to be changed.

Russ