Tap water vs RO water values

[Jabbe]

Hello!

I am new to the hobby, and currently preparing to start my first tank.
I have installed an RO unit in the basement for pure water, but out of curiosity I tested my water for some values before and after the RO unit using the JBL Testlab Marine kit.

I just recently drilled my own well, so my tap water is fresh from the rocks/mountains below (about 100 meters down), so there is no chlorine or any other stuff in it, but as I've read, an RO unit is still highly recommended to filter out phosphates, copper etc.

The "problem" with my RO unit is that the water is really cold, so I get very little water pr day, so filling my tank will take a couple of weeks if I dont run the RO unit 24/7, which I can't.

I tested for NO2, NO3, PO4, CU and for fun dKH (becasue why not, it was a colorful test), and here's what I found. There was no difference in any of this from before and after the RO unit (except dKH).

Here's what I found, and these values were the lowest my test kit went (these were the same results for both the tap water and the RO water, there was no difference):

NO2 = <0.05 ppm
NO3 = <0,5 ppm
PO4 = <0,2 ppm (or pretty much nonexistent as the test kit didn't go lower and there was no color at all)
CU = <0,1 ppm (or Nonexistent again as again there was no color and 0,1 is the lowest the test kit goes.)

And for fun dKH was at 7 from my tap water and 3 from the RO unit.

So my question is, with these results, is it okay to use my tap water to fill the tank (130 gallons) the first time, and then use the RO water for water changes and top-offs? Since there is no phosphates or copper present at all?

Thanks!
Jan-Alfred

[mcgyvr]

It may be possible to not use an RO unit at all..ever... if you water is good enough...
Many do it without problems.. Others simply cannot..
Without a complete water analysis your guess is as good as ours though..

I'm also not sure that those test kits are accurate/usable in both freshwater and saltwater.. Many say they aren't..

We use RO/DI because its just a way to hope that whatever is in the tap water is not used in our tank water..

If I was you and wanted to still use RO/DI then I think I would try to do a long loop of tube to hope to warm the water before its fed into my water filter.. Maybe incorporate a solar heater loop or something.. Then only making water when the sun is out or whatever..

[braappn]

If you choose to go with the RO, a booster pump is what you need. I have a similar situation with mountain well water, very cold and low pressure too. Booster pump hums right along at 80psi with normal production rates.

As for your question on the initial fill though, my guess is no better than yours.


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[hkgar]

You need to be testing the TDS (total dissolved solids) of the water after the RO. Since you do not use the DI initials, can I assume you do not have that cartridge?
Most reefers believe that to remove any possibilities of a contamination your TDS reading should be 0.