TDS meter showing 7. Is that ok level???

[pool guy]

I just finished running a tank of rodi water, and checked it. My hanna tds meter is reading 7. Is that ok or should I change the filters and dump the water and make new ??

[Dozer1one]

my tap water reads under 4, dump it

[pool guy]

CRAP.... not what I wanted to hear.... LOL thanks

[pool guy]

Just tested my tap water... came in at 345 ppm ?????? Is that just really bad water or am I missing somthing ????

[Breadman03]

I've never seen my tap under 370. I read a post from one of the vendors and seem to recall them saying that up to about 800 TDS is normal.

[tanzer16]

Wow! That sounds really high. I tested my tap water when I first installed my rodi unit, and it was 22 ppm

[SquigglyFrog]

My tap averages 270-300... my old place was about the same too.. so i figure if my TDS reads 4, well im not going to worry.. if Dozers tap water reads under 4, then you should feel extraordinarily amazed.. and your one of a select few who has tap that clean..

[disc1]

TDS can only tell you if the RODI filter is working properly. If it is it should produce water at zero. If it produces more than that then something is not optimal in the filter.

TDS numbers can't tell you anything about how suitable the water is for the tank because it doesn't tell you anything about WHAT that is. If just 0.5% of the 7ppm TDS you're talking about is copper then it will nuke the tank of inverts. However if you were to measure the saltwater that your corals live in it would measure 35000 on a TDS meter. So see, it isn't the TDS number that matters. It is what is in that water that matters. There's something. You know there's something because you measured it on a TDS meter. Without knowing what that something is nobody can ever say whether or not that water is suitable for your tank.

[loki6969]

I use a dual TDS meter and going in is 375 coming out is 0 if it ever gets higher than 4 or 5 I change the filters usually the DI first

[Dozer1one]

Any thing over 0 i would change out, But the DI is the last stage of the filters ,so do change that, but also change your Ro's, the Ro removes 90% more than the di does the DIs main job is removing the heavy metals so when it goes bad you can bet the ROs are as well

[Dozer1one]

Also make sure to measure the water coming from the unit itself not your container, containers could leach diff things into your water, this way you narrow it down to your filters

[Laddy]

Originally Posted by disc1

TDS can only tell you if the RODI filter is working properly. If it is it should produce water at zero. If it produces more than that then something is not optimal in the filter.

TDS numbers can't tell you anything about how suitable the water is for the tank because it doesn't tell you anything about WHAT that is. If just 0.5% of the 7ppm TDS you're talking about is copper then it will nuke the tank of inverts. However if you were to measure the saltwater that your corals live in it would measure 35000 on a TDS meter. So see, it isn't the TDS number that matters. It is what is in that water that matters. There's something. You know there's something because you measured it on a TDS meter. Without knowing what that something is nobody can ever say whether or not that water is suitable for your tank.

David, once in a great while someone posts something here which bears repeating. This is such a post, and worth re-reading.

[pool guy]

^^^ I agree.... thats why I read it twice !!!

Thanks for all the input everyone. I ordered new cartridges already. I'm gonna need a lot of water for my upgrade. I plan on just using all new water for cycling in the new tank upgrade. 1/2 new dry rock aquascaped, seeding it with about 20 lbs of lr from the existing tank, and all new sand.

My fishy's will be a little cramped for a little while in their temp tank (75 gallon) but hopefully they will enjoy their new home when all is said and done....

[Buckeye Hydro]

A TDS reading of your DI water higher than 1 ppm IS NOT an indicator that your prefilters or your RO membrane needs to be changed.

A good rule of thumb is to replace your sediment filter and carbon block after six months. A more precise way to maximize the usable life of these two filters is to use a pressure gauge to identify when pressure reaching the membrane starts to decline. This is your indication one or both of the filters is beginning to clog.

Also be cognizant of the chlorine capacity of the carbon block. A good 0.5 micron carbon block for example will remove 99% of the chlorine from 20,000 gallons of tap water presented at 1 gpm. Some original equipment suppliers commonly provide carbon cartridges rated at 2,000 to 6,000 gallons. Remember that all the water you process, both waste water and purified water, go through the carbon block.

Regarding your RO membrane and DI resin, use your total dissolved solids (TDS) meter to measure, record, and track the TDS (expressed in parts per million [ppm]) in three places: 1) tap water, 2) after the RO but before the DI, and 3) after the DI.

The TDS in your tap water will likely range from about 50 ppm to upwards of 1000 ppm. Common readings are 100 to 400 ppm. So for sake of discussion, let's say your tap water reads 400 ppm. That means that for every million parts of water, you have 400 parts of dissolved solids. How do we go about getting that TDS reading down to somewhere near zero?

If you do some experimenting with your TDS meter, you'll note that your sediment filter and carbon block (collectively called “prefilters” because the treat the water before it reaches the membrane) do very little to remove dissolved solids. So with your tap water at 400 ppm, you can measure the water at the “in” port on your RO housing and you'll see it is still approximately 400 ppm.

The RO membrane is really the workhorse of the system. It removes most of the TDS, some membranes to a greater extent than others. For instance, 100 gpd Filmtec membranes have a rejection rate of 90% (i.e., they reject 90% of the dissolved solids in the feed water). So the purified water coming from your 100 gpd membrane would be about 40 ppm (a 90% reduction). Filmtec 75 gpd (and below) membranes produce purified water (a.k.a. “permeate”) more slowly, but have a higher rejection rate (96 to 98%). The lifespan of a RO membrane is dependent upon how much water you run through it, and how dirty the water is. Membranes can function well for a year, two years, or more. To test the membrane, measure the TDS in the water coming in to the membrane, and in the purified water (permeate) produced by the membrane. Compare that to the membrane’s advertised rejection rate, and to the same reading you recorded when the membrane was new. Membranes also commonly produce purified water more slowly as their function declines.

After the RO membrane, water will flow to your DI housing. DI resin in good condition will reduce the TDS in the RO water down to 0 or 1 ppm. When the DI output starts creeping up from 0 or 1 ppm, you know that your resin needs to be replaced. Sometimes people complain that their DI resin didn't last very long. Often the culprit is a malfunctioning RO membrane sending the DI resin “dirty” water. This will exhaust the resin quicker than would otherwise have been the case. Sometimes the problem is poor quality resin – remember that all resins are not created equal.

Additionally, don’t forget to sanitize the entire system at least once per year, and wash and lube your housing o-rings with food-grade silicone grease every filter change.

Russ