help please: water question
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Ron Reefman
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A handheld TDS meter costs about $20. Then you'll know the quality of your water. I have a big, dual membrane RO system that makes 500gpd of zero tds water, so no need for DI. A typical 75gpd or 100gpd system use 1 RO membrane and remove 95-98% of the impurities. If you start with fairly good water, say 300 TDS (tested with your new meter) and the RO makes it 6-10 TDS, that's pretty good and many people would use it. If you add the DI filter it will go to zero TDS.
The issue is this; if you have a TDS of 50 and it's mostly salts and other harmless stuff, it's perfectly OK to use. I used to use water that had a TDS of 30 and a friend used water with a TDS of just over 100 and we both have lps & sps corals and clams. But on the other hand, you could have a TDS of 2 and if it's copper, you will kill off half the stuff in your tank over a fairly short period of time. So a lot of reefers would rather play it safe by having zero TDS. You have to weigh the cost of zero TDS water (a quality and well maintained filter system) against the cost of the things in your tank and the quality of your incoming water. Your local water department may be able to give you a breakdown of what is 'normally' in your water. IMHO, the odds are that good municipal water run through an RO membrane with a TDS under 10 is probably perfectly OK to use... probably. The risk is yours to figure out and decide if you want to take it or not. When I had inexpensive stuff in my early tanks I used water with various TDS. Now my tanks are full of big sps and lps colonies that would cost an arm and a leg to replace, so I have zero TDS water.
The issue is this; if you have a TDS of 50 and it's mostly salts and other harmless stuff, it's perfectly OK to use. I used to use water that had a TDS of 30 and a friend used water with a TDS of just over 100 and we both have lps & sps corals and clams. But on the other hand, you could have a TDS of 2 and if it's copper, you will kill off half the stuff in your tank over a fairly short period of time. So a lot of reefers would rather play it safe by having zero TDS. You have to weigh the cost of zero TDS water (a quality and well maintained filter system) against the cost of the things in your tank and the quality of your incoming water. Your local water department may be able to give you a breakdown of what is 'normally' in your water. IMHO, the odds are that good municipal water run through an RO membrane with a TDS under 10 is probably perfectly OK to use... probably. The risk is yours to figure out and decide if you want to take it or not. When I had inexpensive stuff in my early tanks I used water with various TDS. Now my tanks are full of big sps and lps colonies that would cost an arm and a leg to replace, so I have zero TDS water.
You can use RO water, no worries.
RO by itself does 90 to 98% of the work, the DI acts as the final polishing filter.
No RO will ever get water to a true 0 TDS by itself, its impossible, it is not an absolute barrier.
One issue though is RO by itself is not particularly effective at removing some contaminants such as all forms of ammonia (nitrates and nitrites), phosphates and silicates. On the flip side DI is also not completely effective at certain things itself either so it is best to use both technologies in conjunction with softened water followed by sediment and carbon filtration at the head of the process to get good reliable 0 TDS water.
Yes, RO is better than tap but it is not as good as distilled water or RO/DI. A good $20-$25 handhekld TDS meter will give you an idea what the TDS level in both the tap and RO water are but TDS is only an indicator telling you something electrically conductive is present in the water, it does not speciate or tell you what that contaminant is. It could be calcium, magnesium, copper, iron , lead, arsenic, nitrates, ammonia, phosphates, silicates or who know what. With good true 0 TDS RO/DI there is no question, you have removed everything and have a good starting point to mix your salt with for the proper levels of everything with no background levels to worry about.
No RO will ever get water to a true 0 TDS by itself, its impossible, it is not an absolute barrier.
One issue though is RO by itself is not particularly effective at removing some contaminants such as all forms of ammonia (nitrates and nitrites), phosphates and silicates. On the flip side DI is also not completely effective at certain things itself either so it is best to use both technologies in conjunction with softened water followed by sediment and carbon filtration at the head of the process to get good reliable 0 TDS water.
Yes, RO is better than tap but it is not as good as distilled water or RO/DI. A good $20-$25 handhekld TDS meter will give you an idea what the TDS level in both the tap and RO water are but TDS is only an indicator telling you something electrically conductive is present in the water, it does not speciate or tell you what that contaminant is. It could be calcium, magnesium, copper, iron , lead, arsenic, nitrates, ammonia, phosphates, silicates or who know what. With good true 0 TDS RO/DI there is no question, you have removed everything and have a good starting point to mix your salt with for the proper levels of everything with no background levels to worry about.
beaslbob
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I used tap for a long time in my tank..,,distiller, but tap none the less. I think RO/DI is best, then RO, then tap...so your half way there. Just keep an extra close eye on your parameters.
Ron Reefman
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I'd agree with everything else you said in your post except the above statement. It is not impossible, it's just not easy or cheap! You certainly can get zero TDS with just RO membranes. You may not like the way you have to do it, but my system has been giving me zero TDS with just a dual RO membrane for about 6 months now.
I have an inline TDS meter and it has been zero since about the 3rd or 4th gallon of finished water. Since then, every couple of weeks I've double checked it with my handheld meter to be sure that the inline meter is still working and not stuck at zero! :wink:. But then most reefers wouldn't be buying the kind of RO system that I have. The RO membranes are 20" long, there are 2 of them and it runs at 120psi off a big pump. My incoming water is city water at 400-450TDS and the reject rate is about 5 to 1 at 18gph.
Get a good handheld TDS meter or better yet a conductivity or resistivity meter like the HM Digiatl COM-100 or AP series. You do not have true 0 TDS water with RO only, it is not possible period.
I too run a different system than most with a booster pump set at 100 psi and I flush with stored DI water but that is neither here nor there, membranes and not an absolute barrier and cannot produce 0 TDS water ever. My tap TDS is around 600 and softened and my RO only is between 2 and 3 TDS with a reliable meter, I don't even look at the inlines. Treatment is my profession and I over the last almost 4 decades I have helped design, commission and train operations and maintenance staff and they will all tell you 0 TDS is impossible with a membrane or ever three or four, they are not absolute barriers. There is always something left.
I too run a different system than most with a booster pump set at 100 psi and I flush with stored DI water but that is neither here nor there, membranes and not an absolute barrier and cannot produce 0 TDS water ever. My tap TDS is around 600 and softened and my RO only is between 2 and 3 TDS with a reliable meter, I don't even look at the inlines. Treatment is my profession and I over the last almost 4 decades I have helped design, commission and train operations and maintenance staff and they will all tell you 0 TDS is impossible with a membrane or ever three or four, they are not absolute barriers. There is always something left.
