Do I need to do a TDS test on a brand spanking new RO DI system?

[ReefBouquet]

Hello!

Thanks for stopping by. This is my mandatory "dumb" beginner question I have just gotten my very first marine tank wet for the first time to do a leak test and she has passed with flying colors! Now, I need to make some more RO DI water for the cycle. I have quality salt ready to mix in, live sand waiting to be prepared, bacteria to dose it with, and sculpted and rinsed the dry rock. Everything is ready to go, except I haven't tested the RO DI water.

Do I need to test the water from my new out-of-the-box 4-stage RO DI for TDS and/or chlorine before filling my tank for the first time and doing my cycle?
For context, I am on a very strict budget and have taken months to get to the point of finally having everything ready for cycling. Equipment is more expensive in New Zealand than in the USA, so if I don't need an item or test now I'll save up for later. I have tried searching Google and called the nearest fish expert. The LFS told me not to bother testing the new unit's water for a few months/until filters start getting used up. They only test in-line TDS and don't bother with the chlorine at all, but I imagine their kit is bigger than my 100gpd 4-stage and they probably have multiple carbon filters. I have a cheap TDS-3 tester on the way but it won't do chlorine. Can I rely on the cheap tester or should I make the hike to the LFS for a test? Do I even need to test it out of the box with new filters? When should I start testing the carbon block water for chlorine?

Details:
Tap water averages: pH: 7.8 Fluoride(mg/L): 0.73 Chlorine Residual(mg/L): 0.65 TDS(mg/L): 106 (mg/L is an approximate equivalent to ppm)
RO DI: Aquatic Life Twist-In 100GPD
Tank: 20G WaterBox Cube w/ AI Prime
Planned stock: clowns, a shrimp, CUC, zoa, an anemone (once things are more stable), and maybe a goby of some kind.

TIA <3
Amanda

 

[wculver]

Hello!

Thanks for stopping by. This is my mandatory "dumb" beginner question I have just gotten my very first marine tank wet for the first time to do a leak test and she has passed with flying colors! Now, I need to make some more RO DI water for the cycle. I have quality salt ready to mix in, live sand waiting to be prepared, bacteria to dose it with, and sculpted and rinsed the dry rock. Everything is ready to go, except I haven't tested the RO DI water.

Do I need to test the water from my new out-of-the-box 4-stage RO DI for TDS and/or chlorine before filling my tank for the first time and doing my cycle?
For context, I am on a very strict budget and have taken months to get to the point of finally having everything ready for cycling. Equipment is more expensive in New Zealand than in the USA, so if I don't need an item or test now I'll save up for later. I have tried searching Google and called the nearest fish expert. The LFS told me not to bother testing the new unit's water for a few months/until filters start getting used up. They only test in-line TDS and don't bother with the chlorine at all, but I imagine their kit is bigger than my 100gpd 4-stage and they probably have multiple carbon filters. I have a cheap TDS-3 tester on the way but it won't do chlorine. Can I rely on the cheap tester or should I make the hike to the LFS for a test? Do I even need to test it out of the box with new filters? When should I start testing the carbon block water for chlorine?

Details:
Tap water averages: pH: 7.8 Fluoride(mg/L): 0.73 Chlorine Residual(mg/L): 0.65 TDS(mg/L): 106 (mg/L is an approximate equivalent to ppm)
RO DI: Aquatic Life Twist-In 100GPD
Tank: 20G WaterBox Cube w/ AI Prime
Planned stock: clowns, a shrimp, CUC, zoa, an anemone (once things are more stable), and maybe a goby of some kind.

TIA <3
Amanda

I agree with the LFS that the RO/DI solution will work for you and no need to test for chlorine in a new system. I also do not bother to test for chlorine. As far as how frequently you change the filters, it really depends on how much water you run through the system and mineral content of the water you are filtering. At first I replaced every 6 months but really that's over-kill for me. Having sent off my water for ICP testing a few times my filters are over a year old and still show zero on tests.

 

[Geebs19]

I agree with the above on changing filters, its all going to be up to you. My city water is SUPER clean, coming in at 10-20 TDS. My filters last a LONG time. Before this my TDS going into the DI stage was 300+ and burning through filters and DI resin.

 

[ReefBouquet]

I agree with the above on changing filters, its all going to be up to you. My city water is SUPER clean, coming in at 10-20 TDS. My filters last a LONG time. Before this my TDS going into the DI stage was 300+ and burning through filters and DI resin.

I agree with the LFS that the RO/DI solution will work for you and no need to test for chlorine in a new system. I also do not bother to test for chlorine. As far as how frequently you change the filters, it really depends on how much water you run through the system and mineral content of the water you are filtering. At first I replaced every 6 months but really that's over-kill for me. Having sent off my water for ICP testing a few times my filters are over a year old and still show zero on tests.

Thanks so much! Do you think I need to test for TDS out of the box? I guess TDS would only show if the RO DI unit is faulty or not hooked up right?

 

[KStatefan]

I would want to test. A TDS pen in not a very expensive tool to be able to verify that you are at 0 tds prior to making salt water

 

[exnisstech]

I would just install one of these. First probe before di resin will allow you to monitor your filters and membrane for degradation. Second probe to monitor your di resin. I've been running one for a few years and really like bring able to monitor the RO coming out. When tds there starts to climb too much I swap out filters. When tds after di resin shows 1 resin gets replaced. No need to buy color changing resin. Super easy to install.

 

[Gatorpa]

I would just install one of these. First probe before di resin will allow you to monitor your filters and membrane for degradation. Second probe to monitor your di resin. I've been running one for a few years and really like bring able to monitor the RO coming out. When tds there starts to climb too much I swap out filters. When tds after di resin shows 1 resin gets replaced. No need to buy color changing resin. Super easy to install.

Agree it’s well worth the 20 bucks.

The water is likely fine but since you’re on a budget why risk it with starting of with the possibility of getting crap water, then you’ll spend forever trying to figure out why you stuff dies and spend lots of money losing stuff and get frustrated.

The ounce of prevention is worth a pound of cure.

Plus as noted above it makes it easy to monitor the system and know when to change.

Just spend the $20 it will be worth it in the end not blindly having to replace DI resin and carbon filters unnecessaril.

 

[wculver]

Thanks so much! Do you think I need to test for TDS out of the box? I guess TDS would only show if the RO DI unit is faulty or not hooked up right?

It would be hard for an RO/DI unit to be faulty because the water is forced through the cylinders and the only way out is the filter. The those pre filters are also there to help the DI resin last longer so the last step is to squish the cleaned water through that. So while you can test for TDS it's more piece of mind than anything. If it's making any water it should be making it correctly.

 

[PatW]

I would just install one of these. First probe before di resin will allow you to monitor your filters and membrane for degradation. Second probe to monitor your di resin. I've been running one for a few years and really like bring able to monitor the RO coming out. When tds there starts to climb too much I swap out filters. When tds after di resin shows 1 resin gets replaced. No need to buy color changing resin. Super easy to install.

I use one of these too. I have one where the water comes out of the reverse osmosis membrane and one after my first deionization cartridge (I have two). It is easy to set up and really convenient to test.

 

[ReefBouquet]

Agree it’s well worth the 20 bucks.

The water is likely fine but since you’re on a budget why risk it with starting of with the possibility of getting crap water, then you’ll spend forever trying to figure out why you stuff dies and spend lots of money losing stuff and get frustrated.

The ounce of prevention is worth a pound of cure.

Plus as noted above it makes it easy to monitor the system and know when to change.

Just spend the $20 it will be worth it in the end not blindly having to replace DI resin and carbon filters unnecessaril.

If it was just $20 I would spend in a heartbeat!! but... I live in New Zealand, which is literally at the bottom of the world

Here is a screenshot from the only NZ store that I can find that sells them:

I could go through Amazon to save $20, but it's still $45.

 

[ReefBouquet]

Update: The $13 TDS-3 (resoiution of 1ppm, +/-2%) arrived this morning and is showing 64ppm on the tap water (averages in my area are about 100ppm, so this could be right), and the RO DI is showing 0000ppm

If those are accurate, my filters should last a good long while - woohoo!

I will be investing in an in-line tester, psi gauge, and chlorine test strips when I can for sure.

Is this enough evidence or should I make the hike to a LFS and test there too?

 

[Gatorpa]

Update: The $13 TDS-3 (resoiution of 1ppm, +/-2%) arrived this morning and is showing 64ppm on the tap water (averages in my area are about 100ppm, so this could be right), and the RO DI is showing 0000ppm

If those are accurate, my filters should last a good long while - woohoo!

I will be investing in an in-line tester, psi gauge, and chlorine test strips when I can for sure.

Is this enough evidence or should I make the hike to a LFS and test there too?

I’d go with that.

Also Cl- off gasses very quickly so if the water sits for a fair amount of time any (likely minimal) amount of Cl- should off gas.

You could check it for piece of mind.
run a test on tap water then the rodi
then let a bucket of tap sit for a day and retest..

 

[ReefBouquet]

I’d go with that.

Also Cl- off gasses very quickly so if the water sits for a fair amount of time any (likely minimal) amount of Cl- should off gas.

You could check it for piece of mind.
run a test on tap water then the rodi
then let a bucket of tap sit for a day and retest..

Great idea! I'll remember this, thanks. I also got some free carbon (as an optional extra for the tank filter), so that could be a useful backup to keep handy. I'll keep it in the cupboard in case it's needed.

 

[AydenLincoln]

I’d test it just to be sure! I like these: https://a.co/d/fxM3bJ4