RODI DI depletion rate?

polywise

polywise

OLD SCHOOL-ish
I am a bit confused with the results I am seeing.
I have my DI unit post RO membrane,
TDS post RO are in the single digits
TDS POST (NEW) DI resin read 0
I use a refillable DI filter
water changes are 50 gallons / week

My question is how long should the DI resin last?
After 200 gallons of water changes my TDS reading are in the 3-4 range?
Is this a normal rate? I feel it should be lasting longer

what do you think?
 
Yes, that's too quick for DI resin with the TDS readings of your RO output.

There's several possibilities:

You're on well water that has a high dissolved CO2 content; that can wipe out a DI cartridge in a big hurry.

You've got a channel in your DI resin bed, which allows some of the RO water to by-pass the DI bed. To fix this, simply remove the cartridge, fill it with water at the sink, stir the resin around and let it re-settle.

You've got a displaced gasket at the top of the DI cartridge housing - same issue as above, it allows some of the RO water to by-pass the DI bed.

You had questionable DI resin at the start - this sometimes happens, though it's unusual.
 
Mines the same way, single digits on the RO but the DI is depleted at around 120-130 gallons. It's the most annoying thing. Mines a new spectrapure unit installed in January and it's on its 3rd DI cartridge.
 
it could definitely be co2. you can try something and see if it works for you. after the RO filter run the line into a holding container with a powerhead pointing up at the surface and let it run overnight, it will gas off the co2. then put a small pump in the same container and run it through the di resin into the final holding container. that will guarantee that you don't have any co2 in the water and your resin will last a lot longer.
 
Do you flush the membrane before making DI water? I check my TDS before and after the DI cartridge with BRS meter. If I don't run the water for several minutes to clear the TDS creep, I send water into my DI cartridge that has 450 TDS! After running for several minutes the water entering the DI cartridge is normal - about 10 tds out of the membrane.
 
If you don't flush the ro filter for somewhere between 1/2 hour and 2 hours (not sure) you'll ruin at least one and maybe two DI resin containers. A new RO filter should produce water with 0 tds. If its not either your tap water is really dirty or the filter is not hooked up right.
 
Eric45 said:
If you don't flush the ro filter for somewhere between 1/2 hour and 2 hours (not sure) you'll ruin at least one and maybe two DI resin containers. A new RO filter should produce water with 0 tds. If its not either your tap water is really dirty or the filter is not hooked up right.
Click to expand...

If you mean a new RO membrane, yes, it's a good idea to let it run for 30 minutes or so. But unless one's feed water is very, very high in dissolved ions (>400 ppm, for example), it shouldn't be necessary to disconnect the DI canister from the RO stage every time you use it, though it is a good idea to discard the first gallon or so when you use the system.
 
c02.

I have the same problem, a DI cartridge only lasts for about 100 gal. I added a second di cartrage and just replaced the DI constantly.

Once I got tired of throwing away all of the money I added a degassing station. I just pump the water R/O into a container, which has a big air pump and two big air stones in it. It is covered and the air pump runs 24/7. When I need water, it run it through DI from the degassing barrel (gravity feed - aqualifter pump would work well if you can't use gravity).

It is kind of a pain getting going, but then really has no downside moving forward. I just keep the RO water barrel full, and when I need water, I turn a valve with the 100g of RO water through DI.
 
That's one way to do it, and there are two more. One can set up a trash barrel with an auto top-off unit and an airstone, and use a pressure pump specifically made for RODI units to pump from the barrel through the system.

One can also purchase an in-line degasser. These devices apply a vacuum on one side of a gas permeable membrane, with the water running on the other side.

Both of the above are definitely higher in up-front costs, but more automatic.
 
DieselJunkie said:
c02.

I have the same problem, a DI cartridge only lasts for about 100 gal. I added a second di cartrage and just replaced the DI constantly.

Once I got tired of throwing away all of the money I added a degassing station. I just pump the water R/O into a container, which has a big air pump and two big air stones in it. It is covered and the air pump runs 24/7. When I need water, it run it through DI from the degassing barrel (gravity feed - aqualifter pump would work well if you can't use gravity).

It is kind of a pain getting going, but then really has no downside moving forward. I just keep the RO water barrel full, and when I need water, I turn a valve with the 100g of RO water through DI.
Click to expand...

When did you last replace your ro membrane?
 
Do you know what your water pressure is?

DIresinlifeatvariousrejectionrates_zpse78535ed.jpg
 
I'm having the same issues with my DI resin. I recently got a new BRS 75gpd, and need to replace the resin after about 100 gallons produced. I'm on city water.
 
Hi - Im just getting a chance to read all of the responses.
I'm on well water. I'd bet its CO2 gas..
I have booster pump.
looking for something more automatic.

dkeller_NC, do you have any info about the in line degassed?
 
polywise said:
Hi - Im just getting a chance to read all of the responses.
I'm on well water. I'd bet its CO2 gas..
I have booster pump.
looking for something more automatic.

dkeller_NC, do you have any info about the in line degassed?
Click to expand...

You'll find quite a range on scientific equipment sites like cole-parmer, fisher scientific and others. Search for "in line filter degassers". They're designed for high pressure liquid chromatography set-ups, and probably aren't all that practical for the average reefer, though an awful lot of gear from the laboratory sciences has been appropriated by the reefing community over the last decade or so.

If I had the issue, my preference from the standpoint of automation and relative simplicity would be to use an automatic refill device like Tunze's RO water controller (here) and a pressure pump intended for RODI applications like this. I'd set up a trash can with the Tunze unit feeding it tap water, add a small air pump and air stone, and use the pressure pump to feed the RODI unit. Not totally automatic in that you'd have to shut off the booster pump and air pump when you were done making RODI, but pretty simple and robust.
 
I have got to think about this for a bit.
I like keeping it simple..with regards to too many steps that could fail If I forget to do something and cause a flood..
 
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