RODI questions

[flixxx]

Hello,

i've got an RODI question because i think i'm doing something wrong.

I have a 4 stage RODI, sediment, carbon, RO and DI membrane.

I have a dual TDS meter.
Inlet 1 plugged in after the carbon/before the RO
Inlet 2 plugged in after the RO membrane

Before the RO, I get 50 PPM reading from my TDS
After the RO, it's at 0.

I bought the system used in November, I recently had to change the RO membrane and DI resin because the DI got brown and the RO started reading a 1 PPM instead of 0.

My pressure gauge reads 30 psi (I know it's low), but when I bought a seperate pressure gauge from home depot it read 50. The pressure gauge i bought plugged straight into the source. (In this cause source is a hose connector, that's how i'm plumbed)

My question ARE:

What's the purpose of the DI unit then if I'm getting a 0 reading?
Is it possible that my gauge on rodi is broken, or does the pressure reduce when it goes to the 3/8 hose?
How often should the RO membrane and DI resin be replaced?


Note: I've read the FAQ on this site for RODI, some of my findings don't align with the FAQ.

 

[frog.pauley]

Most folks water will come out of the ro membrane with a couple ppm, the DI finishes it off to O ppm. Now if your reading 0 out of the ro membrane and its still using up di resin, I would think the tds meter is not calibrated. I have a brs 4 stage/w di. I bought a pressure gauge from brs, and it is broken, reads zero all the time. Didnt last but around a year or so. The RO membrane can last a long time, years for most of us. I just changed mine after 3 years and only did that because it had been idle for about a year. Until you read 8-10 ppm out of the RO I wouldnt change it. It will burn up resin faster though. I have to replace depth filters constantly from dirty water. Even after the di resin turns color it may still work for a while. I usually order it when it turns completely brown but dont change till i get readings of 1 ppm out of the di.

 

[flixxx]

Most folks water will come out of the ro membrane with a couple ppm, the DI finishes it off to O ppm. Now if your reading 0 out of the ro membrane and its still using up di resin, I would think the tds meter is not calibrated. I have a brs 4 stage/w di. I bought a pressure gauge from brs, and it is broken, reads zero all the time. Didnt last but around a year or so. The RO membrane can last a long time, years for most of us. I just changed mine after 3 years and only did that because it had been idle for about a year. Until you read 8-10 ppm out of the RO I wouldnt change it. It will burn up resin faster though. I have to replace depth filters constantly from dirty water. Even after the di resin turns color it may still work for a while. I usually order it when it turns completely brown but dont change till i get readings of 1 ppm out of the di.

Calibrating, that never occurred to me. I've never done that. Thanks a lot, i'll pick up some calibration solution and get that done.

 

[Buckeye Hydro]

Yeow. Let's back up a little. I think there's some confusion here.

I have a 4 stage RODI, sediment, carbon, RO and DI membrane.

You mean you have a 4 stage RODI, sediment, carbon, RO Membrane, and DI resin.

I have a dual TDS meter.
Inlet 1 plugged in after the carbon/before the RO
Inlet 2 plugged in after the RO membrane

Before the RO, I get 50 PPM reading from my TDS
After the RO, it's at 0.

I'd rather see you use a tds meter with three probes - the TRM1 - so you can measure the feedwater, the RO water, and the DI water. If your meter has only two probes, then I'd pick the RO water and the DI water, rather than the feedwater and the DI.

I bought the system used in November, I recently had to change the RO membrane... because the... RO started reading 1 PPM instead of 0.

even at 1 ppm, your RO membrane was fine and didn't need to be replaced. that's a 98% rejection rate - the high end of what you can expect. Calculate your rejection rate like this:
(feedwater tds - ro water tds)/feedwater tds=
(50-1)/50=
49/50=
98%

My pressure gauge reads 30 psi (I know it's low), but when I bought a seperate pressure gauge from home depot it read 50. The pressure gauge i bought plugged straight into the source. (In this cause source is a hose connector, that's how i'm plumbed)

You want your pressure gauge to read the pressure that actually reaches the RO membrane, while the system is running. Where is your system's pressure gauge mounted?

What's the purpose of the DI unit then if I'm getting a 0 reading?

Your DI resin will remove whatever your RO membrane misses. Remember that very few people in the country have feedwater with a tds as low as you.

Is it possible that my gauge on rodi is broken, or does the pressure reduce when it goes to the 3/8 hose?

Huh? If your gauge is reading AFTER the prefilters, then its likely your prefilters are clogged. This si the first you've mentioned a 3/8" hose - not sure what you're referring to.

How often should the RO membrane and DI resin be replaced?

Your DI resin will last a very long time. If you feed it 1 ppm water, you may get 5,000 gallons from a single DI cartridge. RO membranes typically last 2 to 5 years. Again, with your high quality feedwater, you can expect many years from your membrane, as long as you change your prefilters on schedule.


Feel free to give us a call when you're in front of your system if you need some help troubleshooting.

Russ
513-312-2343

 

[Fishyoga]

The DI stands for de-ionozation. TDS is 'total dissolved "solids"'
example- Sugar and salt both dissolve into water up to a certain concentration, though I do not know the numbers off the top of my head.
Sugar is considered a 'dissolved solid', salt is considered is 'ionized' up dissolving.
What the DI really does is get rid of any other 'ions' in the water, most importantly Cl- and Fl-. Other minerals with positive charges can also be removed this way- Na+, Ca++, Mg++, K+.
Not all substances ionize in water, however, so that is what the RO membrane is for.

For the more experienced reefers here, did I miss anything of importance?
I'm many years out of my chemistry lab.

 

[Buckeye Hydro]

Nice.

I'd not necessary consider chlorine and Flerovium (I had to look that one up!) the most important ions removed by DI resin. Chlorine should have been removed by the carbon prefilter.

 

[Fishyoga]

^^ What's Flerovium?!
You're right, I didn't mean to suggest that Cl- and F- (lol, that's what I meant originally, Fluorine or fluoride ion) are the most important to be removed, just that they are two that could be removed by the DI portion.

Bwahahahahaha! I just looked it up!
Yeah, you definitely want to remove those super-heavy artificial radioactive ions! that would really mess a fish up, give 'em three eyes or something!

 

[flixxx]

Yeow. Let's back up a little. I think there's some confusion here.


You mean you have a 4 stage RODI, sediment, carbon, RO Membrane, and DI resin.



I'd rather see you use a tds meter with three probes - the TRM1 - so you can measure the feedwater, the RO water, and the DI water. If your meter has only two probes, then I'd pick the RO water and the DI water, rather than the feedwater and the DI.


even at 1 ppm, your RO membrane was fine and didn't need to be replaced. that's a 98% rejection rate - the high end of what you can expect. Calculate your rejection rate like this:
(feedwater tds - ro water tds)/feedwater tds=
(50-1)/50=
49/50=
98%





You want your pressure gauge to read the pressure that actually reaches the RO membrane, while the system is running. Where is your system's pressure gauge mounted?


Your DI resin will remove whatever your RO membrane misses. Remember that very few people in the country have feedwater with a tds as low as you.



Huh? If your gauge is reading AFTER the prefilters, then its likely your prefilters are clogged. This si the first you've mentioned a 3/8" hose - not sure what you're referring to.


Your DI resin will last a very long time. If you feed it 1 ppm water, you may get 5,000 gallons from a single DI cartridge. RO membranes typically last 2 to 5 years. Again, with your high quality feedwater, you can expect many years from your membrane, as long as you change your prefilters on schedule.


Feel free to give us a call when you're in front of your system if you need some help troubleshooting.

Russ
513-312-2343

Thanks you very much, this is the type of response I was looking for.

I split my plumbing from the cold water to a 3/4 inch garden hose (I am pretty sure it's 3/4 inch)

The pressure reading is around 44 psi

There is about a 20 foot garden hose attached and then downscaled to a 3/8" hose

The RODI pressure gauge reads 30 psi though

the TDS meter reads 57 ppm after the sediment and carbon.
It then reads 0 ppm out the RO and before the DI.

The Carbon and Sediment were replaced in January
The RO & DI were replaced in mid February.

The DI Resin had a brownish sponge at the bottom. I kept that there, didn't want to remove it.

As you can see in the picture, the DI resin is already browning up. We do have hard water in our area if that makes a difference

 

[Buckeye Hydro]

So the only thing between the two gauges is 20 ft garden hose, x feet of tubing (looks like 1/4" tubing to me, but hard to tell from the pics), and your prefilters (assuming the system gauge reads after your prefilters. The first thing that comes to mind is either your tube feeding the system is too long, and/or your filters are clogged.

Russ

 

[Buckeye Hydro]

Your resin is going quickly because your membrane is performing poorly because your pressure is so low.

 

[shifty51008]

looks like it is a purely H2O optima pro filter, the same one I have. and if thats the case the pressure guage on the unit is plumbed after the carbon filter, before the membrane.

so IMO it looks like the prefilters are clogging up.

 

[flixxx]

I've replaced the carbon and sediment and no change in the pressure. I've also ran it with no filters (took them both out of their tubes) and still no change in the pressure gauge.

I'm going to try a shorter hose and see if that changes anything otherwise I'll buy a new pressure gauge and see what that yields.

If pressure is still low' what other options do I have? (I'd like to avoid a booster)

 

[shifty51008]

I've replaced the carbon and sediment and no change in the pressure. I've also ran it with no filters (took them both out of their tubes) and still no change in the pressure gauge.

I'm going to try a shorter hose and see if that changes anything otherwise I'll buy a new pressure gauge and see what that yields.

If pressure is still low' what other options do I have? (I'd like to avoid a booster)

your only other option is a booster pump if your pressure stays that low. sorry. you want your pressure around 60-70 psi.

 

[Every1jockzjay]

Are u running hot water? Hot water can melt the membrane and also allow contaminents to pass through

 

[dkeller_nc]

If pressure is still low' what other options do I have? (I'd like to avoid a booster)

Depends. If you're in a house (and it's yours), you can usually adjust the pressure reducer on the cold water inlet to your home so that your tap pressure is around 80 psig. That will help your RODI unit enormously, but you may have to replace some worn-out washers on faucets.

 

[Scorpius]

Depends. If you're in a house (and it's yours), you can usually adjust the pressure reducer on the cold water inlet to your home so that your tap pressure is around 80 psig. That will help your RODI unit enormously, but you may have to replace some worn-out washers on faucets.

Or buy a booster pump and not destroy your home's plumbing.

 

[critteral]

I agree. The pressure is too low. You need a booster pump.

 

[flixxx]

Thanks for all the responses. One thing I don't understand though is that if there isn't enough pressure the RO would not work and I wouldn't get a 0 ppm reading, isn't that a correct assumption?

 

[shifty51008]

no, if the pressure is to low then the membrane doesn't work like it should and lets more gunk pass through, but your DI stage will still bring the TDS reading down to 0 as long as it's still good

 

[flixxx]

no, if the pressure is to low then the membrane doesn't work like it should and lets more gunk pass through, but your DI stage will still bring the TDS reading down to 0 as long as it's still good

OK, the ro does bring TDs to 0. From 57 to 0.

I just plugged the gauge after the hose and it reads a high psi.

I lose about 10 + psi between the source and sediment, carbon. I'm wondering what is left to replace that could be causing such a big drop.