High TDS/DI usage

DBR_Reef

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The OP is already using a booster pump. AZDesertRat is using the spectrapure 99% membrane and I think he recently said he is still seeing 99% rejection after 5 years of use and he has very high TDS from the tap.

That is very impressive, but I think that probably has more to do with his source water, in terms of longevity. Even the spectrpure select badged membranes are not tested with 700 tds water.

My recommendation was for a second booster pump to run the two membranes inline
 

DBR_Reef

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I believe he has stated his is over 500 tds.
Well I'm duly impressed, but it is possible he has really low organics even with that reading, and in my experience it is organics (and lack of maintenance leading to scaling) that tend to lead to short membrane lifespans. All of the dow membranes that I have received hit the 98-99% rejection mark, so I'm not sure I would pay the premium for spectrapure testing them, but it is good to know that dow membranes can last that long- I might stop replacing mine quite so often.

But I just don't think the OP is going to get much improvement from putting in new membranes- He is at 93% rejection rate, which is considerably below the minimum dow will send out, so he must have other factors that are bringing his rejection rate down. Even if we assume the worst, and that his membranes would have tested out at 96%, we would still expect a very rough 96% rate from the spectrapure badged membranes, giving roughly 30 TDS product, which is still going to chew through DI resin. Spectrapure tests at 60 psi (this is one reason they have better numbers than DOW- DOW tests at 50 psi, which is going to lower the rejection rate), 250 ppm, 77°F, with a softened water feed (ie ~all the dissolved solids are going to be ionized), and 15% recovery. He is not meeting these parameters, so he probably wont't get the results.
 
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AZDesertRat

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My SpectraSelect membrane is 8.5 years old and still producing 99.4% rejection rate water. That is with 450-800+ TDS softened tap water at 56-60 degrees F and boosted to 95-100 psi.
They are not just rebadged membranes, they also treat them with a proprietary process which improves their performance. There really is a difference. Having owned 5 different RO/DI systems from several vendors over the past several years I can attest to that. I keep log books on what my RO/DI systems do so have lots of documented proof to back it up.

The biggest factor is a good water softener, before the softener my Dow membranes would last 18-24 months maximum. Post softener and using the 0.2 micron absolute rated sediment filter I have yet to change a membrane is 8.5 years.

I never found an off the shelf dry Dow membrane to test better than 97% rejection rate and I have tested many and even taken them over to Watts Premier by my house and had them lab tested.
 

DBR_Reef

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My SpectraSelect membrane is 8.5 years old and still producing 99.4% rejection rate water. That is with 450-800+ TDS softened tap water at 56-60 degrees F and boosted to 95-100 psi.
They are not just rebadged membranes, they also treat them with a proprietary process which improves their performance. There really is a difference. Having owned 5 different RO/DI systems from several vendors over the past several years I can attest to that. I keep log books on what my RO/DI systems do so have lots of documented proof to back it up.

The biggest factor is a good water softener, before the softener my Dow membranes would last 18-24 months maximum. Post softener and using the 0.2 micron absolute rated sediment filter I have yet to change a membrane is 8.5 years.

I never found an off the shelf dry Dow membrane to test better than 97% rejection rate and I have tested many and even taken them over to Watts Premier by my house and had them lab tested.

I don't work for spectrapure, so I don't know that their "treated with a proprietary process" is a load of hooey, but my strong suspicion is that they are just breaking in the membranes using best practices and then testing them. There are way to many companies in this hobby that claim to have some advantage or unique technology that isn't backed up by the facts. I think if they actually had some great process they would have patented it and dow would probably have bought that patent (I checked, they don't have a RO related patent). Until they show evidence or the general process behind the claims, I'm not buying it. That being said getting a properly broken in membrane and the cream of the dow crop may be worth it- even a 1% difference in rejection rates makes a fair difference in DI usage. I'll post what they have said about their select membranes below.

You wouldn't expect to see good rejection rates out of a dry DOW membrane because a membrane takes 24-48 hours of production to fully wet, and until that time is not going to produce the best water.

I 100% agree on the water softener- removal of organics, oils, barium, etc does a lot for membrane performance and life.
 

DBR_Reef

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From Spectrapure:
Just because the membrane has a Filmtec label on it does not mean that it is a good membrane. Many of them exhibit low rejection rates right out of the Filmtec box. Filmtec membranes are actually rated with a minimum specification of 96% rejection and -20% of the stated flow rating. (See the Dow / Filmtec website for details).

SpectraPure guarantees that the rejection rates and flow rates will be within Filmtec specs on our standard membrane series and at or greater than 98% rejection on our SpectraSelect Series (-S-) membranes. It is not an easy or inexpensive result to achieve. It requires a high level of diligent effort on our part to provide this service to our customers and ensure that the membranes are what they are advertised to be.

One additional factor to keep in mind is that a 98% rejection membrane will double the life of a downstream DI cartridge vs. that of a 96% rejection membrane. That 2% difference translates into far less cost per gallon for DI water due to the extended life of the DI cartridges. For anyone that demands high quality RO water or has DI cartridges downstream of the RO membrane the benefits received from purchasing our tested membranes exceeds the small additional cost that must be added to the cost of the membrane.

These are some of the most important reasons why our tested and guaranteed Filmtec membranes are worth the extra money. In our opinion, the extra effort that it takes to test and guarantee the membranes is well worth the extra cost and effort. Any customer that has a DI cartridge(s) installed downstream of the RO membrane will save a great deal of money on DI cartridges due to the reduced usage of the cartridges.
 

AZDesertRat

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I don't work for Spectrapure either but I am quite familiar with the owner and staff. Since water is my profession we have developed a friendship and I do know their process but have an obligation to not reveal anything. There is a difference. I have been through their facility many times, they used to sponsor our local reef club. Even better than their membranes are their DI, the difference for me was amazing. And just two weeks ago I installed their newest resins which they say will last twice as long as the MaxCap which lasts me over a year now. A good rule of thumb for DI is for every 2% you increase the rejection rate you double the life of your DI.
 

DBR_Reef

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I don't work for Spectrapure either but I am quite familiar with the owner and staff. Since water is my profession we have developed a friendship and I do know their process but have an obligation to not reveal anything. There is a difference. I have been through their facility many times, they used to sponsor our local reef club. Even better than their membranes are their DI, the difference for me was amazing. And just two weeks ago I installed their newest resins which they say will last twice as long as the MaxCap which lasts me over a year now. A good rule of thumb for DI is for every 2% you increase the rejection rate you double the life of your DI.
Fair enough, although I appreciate it when companies are a little more open- I and many others see proprietary __ and immediately think the marketing department is having it's fun. And I've tested a lot of products where this is the case.

Do you think the OP would have a tough time getting down below 10tds with his estimated input TDS and no water softener using a single spectrapure membrane?
 

AZDesertRat

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No, but the big question is how long the membrane and DI would last. My guess is it would still be cost effective but they would not see 8+ years out of a membrane, 1+ years out of a 20 oz MaxCap and 3+ years out of a 20oz SilicaBuster DI. That's with a 100G display with 30G sump and a 16G nano and other our "Dry Heat" evaporation is killer so the ATO works overtime.
 

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Well if you go to the DOW Filmtec site the latest 75 gpd membrane is rated at Typical 99 % at 50 psi with a minimum of 96 %. I run DOW because I will note pay the price for the Spectrapure for one ( some places in Canada $99.00 each ). 2. I am getting 99% with my DOW membranes, TDS 355 in and hovers between 3 and 4 out and they are over 2 years old, and that is now with it being Feb, and ground water is just a wee bit cold in Canada. I don't think that the membranes is Spectrapure shines, I believe it is in their DI resign mix's. I have and do use there resigns, the Maxcap before the Silica buster. I just replaced the Maxcap as it started to show 1 to 2 tds after about six months and the Silica buster is still going strong. I also like the fact that Maxcap will remove Ammonia and will alter the water back to a higher PH before going into the Silica Buster and this one is supposed to remove phosphates better than other mixes. Anyhow as for the battle between the Membranes I say go with the one that is cheaper and spend a little more on some higher quality DI resigns.
 

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