View Full Version : TDS Tap Water Reading Low

10/02/2016, 12:10 AM
Not sure if this is the correct place to post but I'm going to throw it out there.....

My tap water is reading 25-38 on my TDS meter. I know this is good news but what further tests or precautions should I take before using this on my tank? I plan on having SPS in my tank.

10/02/2016, 12:56 AM
At 25-38 you should still be using a proper RO/DI unit. Problem is you don't know what that 25-38ppm is. Best to use an RODI.

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10/02/2016, 01:06 AM
At 25-38 you should still be using a proper RO/DI unit. Problem is you don't know what that 25-38ppm is. Best to use an RODI.

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Got it thanks. I'll see if I can get one.

Buckeye Hydro
10/25/2016, 06:47 AM
I'll bet you'd do just fine with an RO only system - but if you opt for an RODI you will get an extremely long life span out of your DI cartridge.

10/25/2016, 07:52 PM
I personally would go for RO/DI, but RO probably would be fine. It's always a bit of gamble, though, to trust what's coming down the pipe. If the water company decides to add some anti-corrosives some day, the DI will be handy.

10/25/2016, 08:13 PM
By using only RO filter you wont get 0 TDS.Ro removes only 90 percent of the impurityes when its new and from 40 TDS you will get with something like 4 TDS.At that low TDS your tap water has you could skip the RO filter and use only the DI resin but as somewhone sugested ,by using RODI filter than that filter and the resin would last a lot.My RODI instalation makes 40 TDS from 500 in the original tap water without the DI filter.Then it reduces from 40 to 0 by using the DI filter.

Silly clownfish
10/28/2016, 08:23 AM
Personally, I don't worry too much about chasing 0 TDS, but I know my well water pretty well (ok that sentence reads funny). I have it tested every year or 2, usually just the $85 county test for the basics, but about every 5 years we spend the $500 for the full lab work up of about 4 pages of substances I can't pronounce. Yeah, that is more expensive than running RO/DI, but I am drinking this stuff out of the tap every day.

I do have high TDS out of the tank - i have hard water, so a lot of that is calcium, which I dutifully remove with my RO/DI and then add back:twitch:

If you have municipcal water, you should be able to get a copy of their test results from them to give you an idea of what issues might be there.

I ran my original reef tank for about 17 years on either striaght from the tap, or RO only. By the time I upgraded that tank, I did have hair algae issues, but I think it had more to do with tank maintenance slipping. Due to the lighting in that tank, I only kept LPS and softies.

All of that said, I did add a DI unit to my RO when I upgraded a couple of years ago.

I think if you do have anything undesirable in your tap water, it will take a while for it to build to problem levels, and take even longer to remedy. Better to start off right.

10/28/2016, 10:42 AM
Most ro membranes get 95% or better purification. Some impurities like copper for example can be lethal at levels as low as 30ppbillion. So,di is a a prudent step IMO. When using di resin 0tds out is critical since impurities can concentrate on the resins and selectively release( ions with lesser charges go first some of which like ammonia can be harmful) when the resin is exhausted.