Would you change your RO membrane?

[Fishingandreefing]

So my membrane is about 15 months old. As I was about to change it, I tested it what the output without DI and it was about 5 after running it for about 5 minutes. (Started high 250s then slowly dropped to 5tds)

This is well within the AquaticLIfe specs if I recall correctly.

Only hassles is to take the DI off, flush it for about 5 mins, then put the di back.

I really don’t want to waste the membrane unless I really have to, is doing this not as ideal/pristine as replacing the new one? To me as long as the output is under 2-3 TDS is acceptable right?

 

[Randy Holmes-Farley Verified Community Expert]

it sounds fine to me.

Reduced flow is the reason to change a membrane, aside from a hole caused by damage where the tds is not dropped much by the passage through it.

 

[afboundguy]

it sounds fine to me.

Reduced flow is the reason to change a membrane, aside from a hole caused by damage where the tds is not dropped much by the passage through it.

I use a pressure gauge for this purpose. If it goes back up after I flush I tend to leave it alone but if it doesn't go back up after I flush it I replace it.

 

[Shirak]

Sounds fine to me based on your starting TDS. Properly cared for RO membrane can last for many years.

I installed a bypass valve I can open and close after the RO membrane and before the DI stages. This allows running the unit without sending initial higher TDS water into the DI until the RO drops to where it should be.
You can get a couple inline on/off valves and T connector or one of those T connectors with the directional flow control built in.

 

[Fishingandreefing]

I went ahead and replaced it. Now it’s worse. After replacing a new RO membrane, it took over two hours to drop down to 9, that usually give me about 10g of RODI. So I was suspecting the carbon and sediment might need replacement even though only 5 months old, so I went ahead and replace them.

Now added the new DI, it’s now 8 and it’s being running for about 35 mins already.

So I went back to the old DI which gave me 2 before replacing, it’s now 8 also so basically seems like the DI is not doing the job or perhaps my TDS meter not working properly or somehow some where got contaminated?

***

 

[Shirak]

You should have 0 after DI if your DI bed is good. Post some pictures of your setup. Most DI canisters are a mixed bed color changing. Blue or purple is the usual starting color and it should change to a yellowish color as it gets used up. You should see a fairly distinct line between the two colors.

RO membrane hard to say. They vary in quality and rejection rates. It shouldn't take hours to drop in TDS though. Makes me wonder if it is installed fully or there is some waste water getting past the o rings and into the RO, or if there is some other issue going on.

 

[Sam7]

a new membrane has to be rinsed clean by running it for awhile says on package to start working correctly

 

[Fishingandreefing]

You should have 0 after DI if your DI bed is good. Post some pictures of your setup. Most DI canisters are a mixed bed color changing. Blue or purple is the usual starting color and it should change to a yellowish color as it gets used up. You should see a fairly distinct line between the two colors.

RO membrane hard to say. They vary in quality and rejection rates. It shouldn't take hours to drop in TDS though. Makes me wonder if it is installed fully or there is some waste water getting past the o rings and into the RO, or if there is some other issue going on.

I know it should be zero in a few seconds if not right away that’s why I am so frustrated now. It’s the new twist kind I can send picture in a few

 

[Fishingandreefing]

Here are some pictures

 

[Fish Fan]

One thing to check is that with those TDS meters the probes must be positioned correctly to read accurately. Double check the orientation of the probe(s) as shown in this video, skip ahead to about 1:19 you'll see what I'm trying to describe:

 

[Shirak]

ah I see. I would start by checking to see if you have the meter thingies oriented in the correct direction in the little T fitting.

Other than that I don't know much about the RO buddie. TFC RO membrane so rejection rate should be pretty good but final RO TDS will depend on the TDS of your tap water. The DI canister looks good so may be just the meter is reading incorrectly.

 

[Fishingandreefing]

One thing to check is that with those TDS meters the probes must be positioned correctly to read accurately. Double check the orientation of the probe(s) as shown in this video, skip ahead to about 1:19 you'll see what I'm trying to describe:

Will do but it’s being set up for a very long time. All I did was just replaced the filters.

 

[Fishingandreefing]

Now it’s down to 2, what a pain with this Aquatic Life unit.

Wonder if anyone clean the HM TDS meter probes?

 

[Fish Fan]

Here's another thought: Do you know what the water pressure is going into the filter? RO filters are at their best when the water pressure is fairly high, like at least 70 psi up to maybe 90 psi, but you don't want to go so high that the plastic fittings start to blow out

 

[Fishingandreefing]

Here's another thought: Do you know what the water pressure is going into the filter? RO filters are at their best when the water pressure is fairly high, like at least 70 psi up to maybe 90 psi, but you don't want to go so high that the plastic fittings start to blow out

But how does it related to the tds output? Excuse me if pressure play a role in this.

This unit being set up for I would say about 5-7 years already, it’s always 0 when I replaced the new DI.

I did just clean the probe with vinegar and RODI based online instruction

 

[Fish Fan]

Well, knowing that your system has been running for some time without a problem does make some of my suggestions less likely, but I'm just throwing out what I can

Pressure does relate to final TDS after the RO (not necessarily the DI) stages. Low incoming pressure can be a cause of poor efficiency, that's why some people need to use an RO booster pump that pushes water to the RODI system with greater pressure to increase the filter's efficiency.

I'm starting to think this may be testing error, and I would encourage you to at least double check the alignment of the probes as I was saying earlier, especially if you've removed them for maintenance recently. They can even be bumped out of position and you'd hardly know it if you don't double check.

Additionally, in a typical setup the first three stages of your RO filter, including the RO membrane itself, usually results in a TDS of like 3 to 5 TDS. Then, the DI stage(s) "polish" that water to zero TDS. If you recently replaced all your media including your DI, the system should still be producing zero TDS water. If the first three stages were failing, and water was coming out at, for example, 50 TDS, your brand new DI resin should still take that 50 TDS water and produce basically zero TDS, you'd just be exhausting your DI media and an alarming and costly rate.

My last thought is that if you have a smaller tank, you could use gallons of distilled water that you can get at any local grocery store, pharmacy, or Mega-Lo-Mart for about a dollar and a half per gallon. You could use distilled water to make new saltwater and to replace evaporated freshwater, at least until you get a handle on your RODI system, which should be cheaper in the long-term.

 

[Fishingandreefing]

I am running a booster. Prob was cleaned then checked again with two probes visible after inserted. Tap water coming in at at about 250ish, after membrane the lowest I got was around 8 and after DI was 2 (still need to flush for like a minute or two dropping from 15 down to 2)

It’s 30 degrees here.

Now all 4 cartridges are new. Only thing I am going to do is wait til another new DI cartridge arrived after the new year to try.

Hopefully just the new di filter was a faulty one or whatever the case maybe.

(I have few hundred gallon water volumes with 5 tanks so I guess meanwhile I am just going to deal with 2tds)

Always something in this hobby