Acceptable TDS
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sailfintang
CMAS Member
I have never actually tested my aquariums TDS only what I get from teh RO/DI unit. Makes me wonder what my TDS is in the tank but I have an in line tester so it would take some finaggling to get ti to test my tank.
Anyhow I always like a reading of 0 to 5 for makeup and top off water. Some people I think have gone upwards of 10 tds.
I found this in an article on google from a reliable source:
Anyhow I always like a reading of 0 to 5 for makeup and top off water. Some people I think have gone upwards of 10 tds.
I found this in an article on google from a reliable source:
I agree, I wouldn't bother testing your display tanks' TDS, just your RO/DI system. I change out filters at different times, but I'm with Sara in staying under 5 (usually under 2 - I'm anal about that, lol).
Frogfish
Community Member
your tank TDS will be off the chart!!!! as others have said due to the salt.
The target TDS for your RODI should be 0. I know many reefers change it out at 1 but others will go as high as 5.
The target TDS for your RODI should be 0. I know many reefers change it out at 1 but others will go as high as 5.
RO/DI should be 0 or very close to it. I change my DI when I first see signs of anything other than 0. The reason for this is DI resin begins to release weakly ionized substances even BEFORE it is exhausted and weakly ionized substances may not show up on a TDS meter. These can include phosphates, silicates and nitrates just to name a few.
Do not follow the mistaken notion that a high final TDS means you need to change the prefilter and carbon. The pre and carbon filters have very little to absolutely no effect on TDS, they are there to protect the RO membrane which is the workhorse of the system. What the membrane does not get DI polishes off. High TDS is normally the result of exhausted DI resin and possibly a worn out or poorly installed RO membrane.
The best way to troubleshoot a complete RO/DI system is with a TDS meter and a pressure gauge. The pressure gauge gives you an idea of the condition of the prefilter and carbon and the TDS meter tells you the condition of the membrane and the DI resin. To determine what needs attention you need to monitor pressure drop across the filters and the TDS readings from your tap water, RO only water before DI and your final RO/DI. I discourage people from buying inline TDS meters since they only give you two of the required three TDS readings, usually only RO TDS and RO/DI TDS and not the important tap water TDS. A handheld is a much better choice since it can be used portable unlike the inlines so you can read your tap, RO, RO/DI, storage barrel or container, the lFS, your neighbors, store bought bottled water etc.
You cannot test saltwater with a TDS meter. The range of most hobbyist grade TDS meters is 999 TDS and some may have a high range which can measure up to 10,000 by tens so are not as accurate in the high range. Saltwater in your tank is easily going to exceed 30,000-35,000 which is way out of range and can contaminate the probe on a TDS meter if it is not cleaned with DI right away.
Do not follow the mistaken notion that a high final TDS means you need to change the prefilter and carbon. The pre and carbon filters have very little to absolutely no effect on TDS, they are there to protect the RO membrane which is the workhorse of the system. What the membrane does not get DI polishes off. High TDS is normally the result of exhausted DI resin and possibly a worn out or poorly installed RO membrane.
The best way to troubleshoot a complete RO/DI system is with a TDS meter and a pressure gauge. The pressure gauge gives you an idea of the condition of the prefilter and carbon and the TDS meter tells you the condition of the membrane and the DI resin. To determine what needs attention you need to monitor pressure drop across the filters and the TDS readings from your tap water, RO only water before DI and your final RO/DI. I discourage people from buying inline TDS meters since they only give you two of the required three TDS readings, usually only RO TDS and RO/DI TDS and not the important tap water TDS. A handheld is a much better choice since it can be used portable unlike the inlines so you can read your tap, RO, RO/DI, storage barrel or container, the lFS, your neighbors, store bought bottled water etc.
You cannot test saltwater with a TDS meter. The range of most hobbyist grade TDS meters is 999 TDS and some may have a high range which can measure up to 10,000 by tens so are not as accurate in the high range. Saltwater in your tank is easily going to exceed 30,000-35,000 which is way out of range and can contaminate the probe on a TDS meter if it is not cleaned with DI right away.
Its a rejection rate . If your tap TDS is 300 and your output is 30 then your at 90% which is good, and your DI will take care of the rest.
Here:
TDS total dissolved solids water quality testing - TDS Meters and Testers
Here:
TDS total dissolved solids water quality testing - TDS Meters and Testers
90% rejection is not good. Most membranes including the most popular Dow Filmtec 75 GPD as well as the GE and Applied membranes are rated at 98% rejection and should be removing 96% at a minimum.
The difference between 90 and 98 % is very dramatic and can be a big cost savings when it comes to DI. A very accurate rule of thumb states "For every 2% you increase the RO rejection rate, you DOUBLE the life of your DI resin". This means increasing the rejection to 98% will make your DI last what, maybe 4 to 8 times longer than at 90%.
The difference between 90 and 98 % is very dramatic and can be a big cost savings when it comes to DI. A very accurate rule of thumb states "For every 2% you increase the RO rejection rate, you DOUBLE the life of your DI resin". This means increasing the rejection to 98% will make your DI last what, maybe 4 to 8 times longer than at 90%.
MY friend is running a straight RO no DI and is getting 2 TDS reading....i am under the assumption that is fine, right?
Hey in the context of the article and calculator I provided a link to, 90% is good. Getting the actual rejection rate out of your membrane is tricky at best, due to Pressure and temperature. I you have a high tap TDS your still going to eat away you DI. Back Off!
I live in Phoenix, my tap water TDS averages 800-830 year round. My RO only TDS is 5.3 to 6.2 using a calibrated HM Digital COM-100 handheld TDS meter. Thats a 99.25 to 99.34% rejection rate with RO only before any DI. Getting good rejection is not tricky at all. Yes water pressure and temperature do have an effect on final TDS but the real keys are using a good membrane and keeping it well flushed by keeping the waste ratio at 4:1. By reducing the waste ratio you shorten the life of the membrane dramatically. Same goes with using low quality replacement prefilters and carbons, thye will not protect the membrane as well so they shorten its useful life. Its sort of a pay me now or pay me later scenario, use cheper replacements and replace the membrane and DI more often or use better replacements and extend the life of the membrane and DI as well as get better final water quality.
High tap water TDS does not mean you will eat DI if you use quality components, many of us prove that every day here in the Southwest. Phoenix TDS varies from a low of 600 to over 1600 and most of us have found nothing matches Spectrapure for quality. Yes I pay more up front but I get tremendous life out of my RO/DI system.
If you are going to tell someone to back off you need to get your facts straight first. Good water quality is possible even with high TDS, high CO2, high sediment or suspended solids etc. Spectrapure has membranes on sale for $35 right now that will give you results like that. Check out the link to the sale flyer in the Group Buy forum or here:
SpectraPure Customer Appreciation SALE! 20% - 50% off
fsu1dolfan, a TDS of 2 from RO only is pretty good but you still have no idea what that 2 TDS is made up of. Certainly better than tap but it can be improved upon for maybe $30 with an add on DI filter kit. The reason its important to have 0 TDS is some contaminants are very weakly ionized and may not register on a TDS meter when present. You could have higher levels of phosphates or silicates and not know it as only some may register. Another drawback to RO only is RO is poor at removing all forms of ammonia including nitrites and nitrates. Some Utilities (roughly 30% in the US) are now using chloramines as a residual disinfectant and the RO will pass the ammonia. DI is what removes the ammonia portion of the chloramines while good carbon gets the chlorine portion.
High tap water TDS does not mean you will eat DI if you use quality components, many of us prove that every day here in the Southwest. Phoenix TDS varies from a low of 600 to over 1600 and most of us have found nothing matches Spectrapure for quality. Yes I pay more up front but I get tremendous life out of my RO/DI system.
If you are going to tell someone to back off you need to get your facts straight first. Good water quality is possible even with high TDS, high CO2, high sediment or suspended solids etc. Spectrapure has membranes on sale for $35 right now that will give you results like that. Check out the link to the sale flyer in the Group Buy forum or here:
SpectraPure Customer Appreciation SALE! 20% - 50% off
fsu1dolfan, a TDS of 2 from RO only is pretty good but you still have no idea what that 2 TDS is made up of. Certainly better than tap but it can be improved upon for maybe $30 with an add on DI filter kit. The reason its important to have 0 TDS is some contaminants are very weakly ionized and may not register on a TDS meter when present. You could have higher levels of phosphates or silicates and not know it as only some may register. Another drawback to RO only is RO is poor at removing all forms of ammonia including nitrites and nitrates. Some Utilities (roughly 30% in the US) are now using chloramines as a residual disinfectant and the RO will pass the ammonia. DI is what removes the ammonia portion of the chloramines while good carbon gets the chlorine portion.
Thanks...i let him know to pick up a DI...great info!
is that city water? if so that is very very good. you sure there is not some sort of prefilter inline with your water supply? i dont think i have ever seen tap water that low any any country reports i have looks at. average is 140-400 and most are in the middle to higher end of that scale
with that said yes i would still have a ro/di unit to bring that down to 0. it will also remove othe things that citys put in tap water
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I often see reports of tap water TDS levels below 50 in the Atlanta area. Even with low TDS you still do not know the makeup of that TDS. At a minimum I would look at a low micron prefilter, carbon block and then DI as final treatment but its hard to beat a good RO/DI system.
Something I have not seen is the suspended solids or TSS listed in Georgia. It could be like the New York area with extremely low TDS but higher than normal suspended solids or particulates but I don't think that is the case.
The average TDS nationwide is in the 250 range with some areas like Washington, Oregon, parts of Georgia, some Canadian waters and New York city much lower than that, often in the 50 range and below. Other areas specifically the Southwest can go over 1600. Here in Phoenix we are influenced by the Colorado River and Salt River systems. You can imagine the mineral content of the Colorado River system when you look at a picture of the Grand Canyon, all that rock and sediment had to go somehwere! And I will give you three guesses as to how the Salt River got its name and the first two don't count! Our water is so hard and high in dissolved minerals you can almost cut it with a knife......
Something I have not seen is the suspended solids or TSS listed in Georgia. It could be like the New York area with extremely low TDS but higher than normal suspended solids or particulates but I don't think that is the case.
The average TDS nationwide is in the 250 range with some areas like Washington, Oregon, parts of Georgia, some Canadian waters and New York city much lower than that, often in the 50 range and below. Other areas specifically the Southwest can go over 1600. Here in Phoenix we are influenced by the Colorado River and Salt River systems. You can imagine the mineral content of the Colorado River system when you look at a picture of the Grand Canyon, all that rock and sediment had to go somehwere! And I will give you three guesses as to how the Salt River got its name and the first two don't count! Our water is so hard and high in dissolved minerals you can almost cut it with a knife......
It's unusual to see a true 0 TDS reading with RO only no matter how well it is performing. RO is not a perfect treatment method and is only partially effective at some things like all forms of ammonia and some others. Likewise most hobbyist grade TDS meters also have limitations such as accuracy in the 2-3% of full range scale and temperature correction problems with inline style meters. If a person uses a conductivity or resistivity meter they find what appears to be 0 TDS really isn't so. Its close enough to 0 for our uses but say in the semiconductor industry it would not be so. I still recommend a final DI filter for just that reason, even if it appears perfect it can still have room for improvement and DI is that improvement. If you are getting an indicated 0 TDS then DI would last a long long time as final treatment.
You also need to keep in mind, we treatment plant operators and supervisors keep coming up with new things to add to your tap water like fluoride in the form of man made acids to control tooth decay and bone problems, phosphates in the form of ortho or polyphosphates for corrosion control, ammonia and chlorine from chloramines and free chlorine or bleach generators as well as others for pH adjustment and taste and odor control. What may seem to be pristine waters may have any number of things in it you may not be aware of and which may not register well on a TDS meter. Just something to keep in mind.
And just keep rubbing salt in the wounds about your good water quality!!! My 830 TDS is just fine if you like water that stands up all by itself.......
You also need to keep in mind, we treatment plant operators and supervisors keep coming up with new things to add to your tap water like fluoride in the form of man made acids to control tooth decay and bone problems, phosphates in the form of ortho or polyphosphates for corrosion control, ammonia and chlorine from chloramines and free chlorine or bleach generators as well as others for pH adjustment and taste and odor control. What may seem to be pristine waters may have any number of things in it you may not be aware of and which may not register well on a TDS meter. Just something to keep in mind.
And just keep rubbing salt in the wounds about your good water quality!!! My 830 TDS is just fine if you like water that stands up all by itself.......
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