I'm having trouble getting my TDS down after the RO stage. My DI is getting depleted really quick. Tap is about 450ppm, after RO is about 50ppm. After DI it's 0-2ppm. I was thinking to run a second RO system after the first in series. Will this work? Do i need a booster pump and a larger drinking water reservoir? Have a is 3gal resevoir i would place in-between the two RO.
Two RO systems in series
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What membrane are you using?
With a 99% spectrapure it will have a drastic difference in output
@AZDesertRat
With a 99% spectrapure it will have a drastic difference in output
@AZDesertRat
Sounds like you need a new RO membrane. My tap TDS is between 560 and 850 and my RO only TDS is between 2 and 3 still with a 9 year old RO membrane.
What is your water pressure, water temperature, water hardness and exact measured waste ratio ? Do you make RO/DI water in nice long batches of 5+ gallons at least every 10-14 days? Do you have a DI bypass valve between the RO and the DI to flush out the TDS creep each time you make water to extend the life of your DI resin?
You aren't using a drinking water pressure tank to make DI water are you? This is a killer of both RO membranes and especially DI resin. If you use it for drinking water too, isolate the DI from the pressure tank with a check valve as shown in Spectrapures Hook Up Diagrams at the bottom of their web page. Look at the Non Air Gap drinking water drawing and note the check valve so the DI comes directly from the membrane and not the TDS creep water in the pressure tank.
Dual membrane systems don't make the water any purer, they run the waste from the first into the second so are a little less efficient than a single membrane plus they require a minimum of 65 psi to operate and higher to be efficient. You don't need that, you need a single better membrane protected by high quality low micron absolute or near absolute sediment and carbon block filters.
What is your water pressure, water temperature, water hardness and exact measured waste ratio ? Do you make RO/DI water in nice long batches of 5+ gallons at least every 10-14 days? Do you have a DI bypass valve between the RO and the DI to flush out the TDS creep each time you make water to extend the life of your DI resin?
You aren't using a drinking water pressure tank to make DI water are you? This is a killer of both RO membranes and especially DI resin. If you use it for drinking water too, isolate the DI from the pressure tank with a check valve as shown in Spectrapures Hook Up Diagrams at the bottom of their web page. Look at the Non Air Gap drinking water drawing and note the check valve so the DI comes directly from the membrane and not the TDS creep water in the pressure tank.
Dual membrane systems don't make the water any purer, they run the waste from the first into the second so are a little less efficient than a single membrane plus they require a minimum of 65 psi to operate and higher to be efficient. You don't need that, you need a single better membrane protected by high quality low micron absolute or near absolute sediment and carbon block filters.
Thanks Guys, great input. I ordered a new RO system from BRS so my drinking and aquarium will be separated. I did have the drinking reservoir directly connected to the DI. There's a pre filter before returning to the line, but it's a tiny filter i'm sure doesn't help.
Don't have a pressure gage on the line but it seems normal, not low.
Temperature is average too, i live 1 mile from the coast in San Diego so it stay pretty constant year round.
Not sure what my hardness is, i can test it tonight.
My current RO is a Watts Premier WP-4V. I thought it was my membrane as it's just 2 years old now. Didn't have a TDS meter when i first installed it. I boughta new membrane but up the GPD from 36 to 75. It now produces higher TDS than the 36GPD but much less waste water ( i use this for a pond so not really wasted )
With 36GPD membrane = 50 TDS
With 75GPD membrane = 100+ TDS
I'll see what the BRS 75GPD give me from the start.
Don't have a pressure gage on the line but it seems normal, not low.
Temperature is average too, i live 1 mile from the coast in San Diego so it stay pretty constant year round.
Not sure what my hardness is, i can test it tonight.
My current RO is a Watts Premier WP-4V. I thought it was my membrane as it's just 2 years old now. Didn't have a TDS meter when i first installed it. I boughta new membrane but up the GPD from 36 to 75. It now produces higher TDS than the 36GPD but much less waste water ( i use this for a pond so not really wasted )
With 36GPD membrane = 50 TDS
With 75GPD membrane = 100+ TDS
I'll see what the BRS 75GPD give me from the start.
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My Tank Thread
Two points:
1, Drinking water Reservoir - This is always kept full by your RO constantly coming on to fill it up. Every time your RO "turns on", there is breakthrough TDS....that ends up in the reservoir. You should not be using this water to run through your DI....the TDS is too high from the breakthrough. Tee off the line between the membrane and reservoir and make your water for your tank that way.
2. Changing Membranes with different output - If you change the membrane with a different output, you also need to change the restrictor. There are two kinds of restrictors (that I know of). One is a capillary tube type that you trim to "fit" your membrane, and then there is the inline type. So you will need to get the proper restrictor with that new 75 GPD membrane. That is why your waste water volumes are way off.
Hope this helps.
1, Drinking water Reservoir - This is always kept full by your RO constantly coming on to fill it up. Every time your RO "turns on", there is breakthrough TDS....that ends up in the reservoir. You should not be using this water to run through your DI....the TDS is too high from the breakthrough. Tee off the line between the membrane and reservoir and make your water for your tank that way.
2. Changing Membranes with different output - If you change the membrane with a different output, you also need to change the restrictor. There are two kinds of restrictors (that I know of). One is a capillary tube type that you trim to "fit" your membrane, and then there is the inline type. So you will need to get the proper restrictor with that new 75 GPD membrane. That is why your waste water volumes are way off.
Hope this helps.
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You might cancel your order and research the Spectrapure Select Series 99% guaranteed membrane someone mentioned. Read their FAQ section on their website, you will be amazed at how much money it will save you in the first year alone. For every 2% you gain as in the normal 96-97% most membranes produce to the 99 or 99+% theirs does you double the life of your DI. My Select membrane is 9 years old and still at 99.4% rejection rate. The MaxCap DI lasts over a year and SilicaBuster 3 years. That is with 560-850 TDS going in and a 100G with 30G sump and a 16G nano with lots of evaporation in Phoenix. You will be glad you did, look them up.
Also, there is absolutely no reason in the world for two systems. Use your existing ASOV and drinking water kit but follow the directions I mentioned earlier and isolate it with a $5 check valve. Simple and effective.
Thanks AZDesertRat, Good points. I'll take a look at Spectrapure and get myself a check-valve. My current system looks like it's a manifold design so i can't access the prefilter output right before the membrane. I'll see what i can do to fix this.
How are you testing TDS, where are the samples being drawn from and what are you testing it with and in? Have you checked calibration on your meter or at least tested some distilled water to see if it is 0 or very close? Do a search with my username and TDS testing for my suggested method.
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Thanks AZD, I searched and see you're very active :) Thanks for all the support you give everyone. I'm reading it form a tap off valve right before the DI.
I use a hand-held TDS meter. But i don't think it's temperature sensitive. Do you have a recommended meter to buy? RO/DI reads 0 or very close to it, (sometimes it bounces to 1 maybe due to dirty container? Usually a plastic cup.) RO reads low 20's still.
I'm going to get a inline one just to constantly regulate the in/out of the DI and use the non-color changing resin like you've suggested elsewhere. I dump it after the color has changed only to fine i have strips of unchanged resin. Wasted resin :(
After your suggestions my system is much better!! i'm not burning DI nearly as fast after water changes. I'm only making it in batches now and no reservoir inline. I'm still at low 20's TDS but this should be better right? I'm using DOW's 99% rejection from BRS, maybe i should swap with the Spectrapure Select Series you've suggested.
I use a hand-held TDS meter. But i don't think it's temperature sensitive. Do you have a recommended meter to buy? RO/DI reads 0 or very close to it, (sometimes it bounces to 1 maybe due to dirty container? Usually a plastic cup.) RO reads low 20's still.
I'm going to get a inline one just to constantly regulate the in/out of the DI and use the non-color changing resin like you've suggested elsewhere. I dump it after the color has changed only to fine i have strips of unchanged resin. Wasted resin :(
After your suggestions my system is much better!! i'm not burning DI nearly as fast after water changes. I'm only making it in batches now and no reservoir inline. I'm still at low 20's TDS but this should be better right? I'm using DOW's 99% rejection from BRS, maybe i should swap with the Spectrapure Select Series you've suggested.
Don't waste your money on an inline TDS meter, it will not be as accurate as what you have now.
Good TDS meters in the $25-$30 range are the HM Digital TDS-3, TDS-4TM or AP-1. If you want extremely accurate their COM-100 is by far the best at around $60.
Spectrapures Select membranes are individually hand tested and guaranteed 99% or better, the one you bought is not tested nor. guaranteed in writing, it is a typical number but usually not attainable
Dow says most of their membranes should be 98% but in reality people who have tested them over the years find it to be 96-97% on average. For every 2% you can gain you double the life of your DI. I would forget color changing resin too, it very unreliable. Before I discovered MaxCap and SilicaBuster non color changing resins I was going through a 20 refill every 150 gallons and that was letting the DI TDS get to 3-5. Now I get 1000+ gallons out of a MaxCap before I see 1 TDS and 3000+ out of the SilicaBuster before I see 1 TDS in the finished water, they really know their stuff and have over 30 under their belts to prove it.
Good TDS meters in the $25-$30 range are the HM Digital TDS-3, TDS-4TM or AP-1. If you want extremely accurate their COM-100 is by far the best at around $60.
Spectrapures Select membranes are individually hand tested and guaranteed 99% or better, the one you bought is not tested nor. guaranteed in writing, it is a typical number but usually not attainable
Dow says most of their membranes should be 98% but in reality people who have tested them over the years find it to be 96-97% on average. For every 2% you can gain you double the life of your DI. I would forget color changing resin too, it very unreliable. Before I discovered MaxCap and SilicaBuster non color changing resins I was going through a 20 refill every 150 gallons and that was letting the DI TDS get to 3-5. Now I get 1000+ gallons out of a MaxCap before I see 1 TDS and 3000+ out of the SilicaBuster before I see 1 TDS in the finished water, they really know their stuff and have over 30 under their belts to prove it.
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