350 PPM TDS before RO, 10 PPM after RO, 0 PPM after DI - Chewing through Resin

[Chocobo]

Hey guys.

My tap water has 350 PPM TDS which seems pretty terrible.

I have a Bulk Reef Supply 150 GPD 6 Stage RO/DI and am seeing 10 PPM after the RO and 0 ppm after DI but it’s absolutely chewing through DI resin.

I have the auto flush which is a 500 ml/min restrictor which is what BRS recommended for this unit. I’m wondering if I should be using a higher flow restrictor like 700-800 ml/min due to how high the TDS is in the source water?

[Chocobo]

I am going to try running both 75 GPD membranes in parallel. I will have more waste water per minute but will maintain 1:4 ratio. I estimate each membrane should be able to produce 200 ml/min clean water for a total of 400 / min.

This hopefully will help it make sense.

1. City water enters the booster pump
2. Water passes through sediment filter
3. Water passes through carbon block 1
4. Water passes through carbon block 2
5. Water split into two lines - each feeding a membrane.

RO filtered water output from membranes is joined back together into a single line and enters de-ionization and then RO/DI storage.

Waste water leaves each membrane and each goes to a different restrictor - one 800 ml/minute normal restrictor on one line and one 800 ml/minute auto flushing restrictor on the other line.

The waste lines are joined together before the restrictor pair so that when the auto flush happens both membranes get flushed through this line. When the auto flush is not flushing a combined 1600 ml/minute will be going down the drain.

Each membrane should in theory produce 200 ml/minute of filtered water before DI and 800 ml of waste water for a 1:4 ratio.

Booster pump should be able to push the pressure to make running this in parallel feasible.

I expect to have the parts needed to test this by Tuesday and will definitely update this thread.

If anybody has any suggestions or questions let me know. I don’t pretend to be an expert but I think I understand this well enough to experiment with this a bit.

[tkeracer619]

Which municipality are you buying water from. I'd like to look at the water quality report.

You're getting 97% rejection which isn't terrible but could be improved upon. If you were to get 99% you would be 3-4TDS and almost 3x the DI life.

You need to be running a 4:1 waste to product ratio even with dual inline membranes unless you have softened water. Often people feel like they can run 2:1 with dual membranes but that isn't ideal.

When flushing the membrane you don't need a restrictor at all, you should be flowing as much water through the waste as possible.

What booster pump are you using? That is a lot to ask for most pumps.

[Chocobo]

Originally Posted by tkeracer619

Which municipality are you buying water from. I'd like to look at the water quality report.

Not sure off hand I don't pay for the water here.

Originally Posted by tkeracer619

You're getting 97% rejection which isn't terrible but could be improved upon. If you were to get 99% you would be 3-4TDS and almost 3x the DI life.

Indeed.

Originally Posted by tkeracer619

You need to be running a 4:1 waste to product ratio even with dual inline membranes unless you have softened water. Often people feel like they can run 2:1 with dual membranes but that isn't ideal.

According to BRS, when I ordered the auto valve, they suggested the 500 for the Dual 75 in Series - I really think it should be 800.

Originally Posted by tkeracer619

When flushing the membrane you don't need a restrictor at all, you should be flowing as much water through the waste as possible.

Indeed - but as I am feeding the whole system with a single 1/4" line I think a single full-flush line should work.

So when it's not flushing there will be two restrictors in parallel for a total of 1,600 ml/min of waste water which should be 4:1 to the 400 ml/min of permeate.

When it is flushing - the water will take the path of least resistance which will be the auto-flushing restrictor which will be fully open and not restricting. I planned on joining the waste lines together after the restrictors as well.

I don't trust having two separate auto-flushing restrictors to be timed perfectly with each other. Joining the waste lines together before the restrictors will allow the water from both membranes to flush down a single line without restriction periodically.

Originally Posted by tkeracer619

What booster pump are you using? That is a lot to ask for most pumps.

The Aquatec 8800. I have it dialed back as my source water pressure is pretty good. Dow says that their FILMTEC membranes, which is what I have in this system, should only drop the pressure 4~5 PSI per membrane. I have the 8800 turned down more than 10PSI from stock just to keep from over-pressuring the membranes as it is.

Worst case - I just go single membrane and live with it producing permeate and waste at 1/2 the speed - but either way I will be running an 800 ml/minute restrictor [and/or will test permeate to waste ratio and get a restrictor that's appropriate for the membrane and pressure].

[Pet Detective]

With that high of TDS in your municipal water, you are going to either replace your membrane more often or go through DI resin quickly, my city water is about 165 out of the tap and I usually get 18 months of good service from my membrane, when my DI resin depletes more rapidly, I know it's time to replace the filmtec 75gpd.

On the flip side....you can regenerate your DI resin for pennies on the dollar as opposed to buying new DI cartridges, I won't bore you with with the procedure here but all you need is sodium hydroxide [lye] & muriatic acid, neither of which cost more than $7, just google it, you will find detailed instructions, it takes about 2 hours to accomplish, I do this usually every 12-18 months....I have about 7 catridges worth of DI resin, so doing the math I usually get 2 full months + or - from my resin before changing it out.

[Chocobo]

Originally Posted by Pet Detective

With that high of TDS in your municipal water, you are going to either replace your membrane more often or go through DI resin quickly, my city water is about 165 out of the tap and I usually get 18 months of good service from my membrane, when my DI resin depletes more rapidly, I know it's time to replace the filmtec 75gpd.

On the flip side....you can regenerate your DI resin for pennies on the dollar as opposed to buying new DI cartridges, I won't bore you with with the procedure here but all you need is sodium hydroxide [lye] & muriatic acid, neither of which cost more than $7, just google it, you will find detailed instructions, it takes about 2 hours to accomplish, I do this usually every 12-18 months....I have about 7 catridges worth of DI resin, so doing the math I usually get 2 full months + or - from my resin before changing it out.

I had no idea. I’ll google it. That said I would like to avoid changing them out a lot so if recharging them is a solid process I’ll probably get the longer cartridges.

[OrionN]

Spectrapure have ultra rejection membranes 90gpd which reject about 99+ of impurities. I use this membrane. It is only a little more expensive then the regular membrane. You should consider using this membrane.

[Chocobo]

Originally Posted by OrionN

Spectrapure have ultra rejection membranes 90gpd which reject about 99+ of impurities. I use this membrane. It is only a little more expensive then the regular membrane. You should consider using this membrane.

Is it a direct swap in the BRS housing?

[Pet Detective]

Originally Posted by Chocobo

Is it a direct swap in the BRS housing?

They all are "size" of housing compatible, the most common size is the 10" canister, which is most likely what you have, so just make sure the membrane is the same length and it will fit, most all "brand" name RO/DI units use compatible housing, it's just their name that is different, same goes for membranes, difference being GPD & rejection rates, and carbon blocks and sediment filters, difference with those are the micron ratings, basically.

I stick with Filmtec when it comes to membranes but I have no experience with Spectrapure brand, it might be fantastic, check online for reviews.

[OrionN]

You need to make sure the flow restrictor is rated for 90 GPD membrane. If this is the case, just swab is fine, however, if it is not, you need to get the flow restrictor rated for this membrane.
RO membranes need specifically rated flow restrictor to work properly. I am sure you can ask Spectrapure. However, just to be safe, spend a few dollars and get the correct flow restrictor for it.

[tkeracer619]

Yup it will fit.

I use them and am getting around 99.5% rejection with two in series.

145in and 0-1out.

I use an adjustable needle valve for a restrictor. Water temp varies here dramatically season to season so I adjust it as temps change.

[tkeracer619]

Originally Posted by Chocobo

Not sure off hand I don't pay for the water here.

You'll need to test your RO waste water for total ammonia to see if you have chloramines unless you can find out where the water comes from. If you do, this will degrade your entire system rapidly. About 30% of the country uses it and if you are unlucky like me you have chloramines in water over 7.5 ph... which wrecks systems not up to the task.

You can go to walmart and get one of the cheep jungle buddies ammonia test strips. It will react to chloramines. Test your RO waste water. Many ammonia test kits will not register since they only test free ammonia. Please report your findings. For me after redoing my system with dual 99% membranes from spectrapure, maxcap DI carts, and a large carbon block for chloramines I went from 200gal per DI cart to 2000gals.
https://www.walmart.com/ip/Jungle-Qu...count/10313043

[Pet Detective]

Originally Posted by tkeracer619

You'll need to test your RO waste water for total ammonia to see if you have chloramines unless you can find out where the water comes from. If you do, this will degrade your entire system rapidly. About 30% of the country uses it and if you are unlucky like me you have chloramines in water over 7.5 ph... which wrecks systems not up to the task.

You can go to walmart and get one of the cheep jungle buddies ammonia test strips. It will react to chloramines. Test your RO waste water. Many ammonia test kits will not register since they only test free ammonia.
https://www.walmart.com/ip/Jungle-Qu...count/10313043

I'm curious, do you use 2 carbon blocks?

Sometimes early in the spring & then again in the fall my municipal water co. will add chloramines to the water if there is an algae or bacteria bloom, I just turned my 4 stage into a 5 stage, using 2 Chlor-Plus carbon blocks by Pentek, just in case, my membrane has lasted quite nicely since.

[tkeracer619]

I use a Size 20 big blue housing with a Chlorplus 20BB in it as my primary. It's a 20lb carbon block that so far has lasted 3 years and over 10,000gal of rodi. I have a spectrapure system after that and it has 2 chlorplus 10 and a .5 micron carbon block as well. I don't think they really do much however but I had them so I used them.

[Pet Detective]

^ Holy Crap....Go Big or Go Home I guess...LOL

[tkeracer619]

Yup, I lost 8 years of hard work in 4 days to chloramines. Go big or quit was the name of the game. Went big

Lost 100% of this tank due to chloramines...

[Pet Detective]

^^ Amazing..... so much sympathy.

I lost a much smaller Reef to a Hurricane, no power for 2 weeks, never go without a generator again, but it couldn't compare to your loss.

I hope you have been able to come close to this again.

[45commando]

OP, have you researched "TDS creep" ? Basically, the RO water produced at start up can be very high in TDS & then drops off as more RO water is produced. If this initial water is going into your DI resin, it will exhaust the resin faster. An in-line TDS meter on the output RO line will show you when it is ok to then divert to the DI resin. Please ignore if you are already aware of this HTH

[FPSD]

Originally Posted by Chocobo

Is it a direct swap in the BRS housing?

Where are you at? I am in NW Indiana. I had same issues. Are you on a well or ?

[FPSD]

BTW. My tds before r/o is 500-600. So your not that high.

[slief]

Originally Posted by FPSD

BTW. My tds before r/o is 500-600. So your not that high.

Yea, Mine ranges from 475 to 575. I’d love to have 350 tds tap water! That said, I get great membrane and cartridge life out of my Spectrapure UHE 1:1 unit.

[tkeracer619]

Originally Posted by Pet Detective

^^ Amazing..... so much sympathy.

I lost a much smaller Reef to a Hurricane, no power for 2 weeks, never go without a generator again, but it couldn't compare to your loss.

I hope you have been able to come close to this again.

Thanks, not yet but I will and then some.

[alton]

see attached

[Chocobo]

Originally Posted by alton

see attached

The membranes I have are 99% Rejection rate [newer Dow Filmtec HR membranes]. I really think the reason I'm at 97% is due to running the membranes in series as well as a 550 ML/min restrictor instead of an 800 ML/min.

Just waiting on parts to show up to do testing.

[OrionN]

I don’t think you can run membrane in series. The output of the first membrane is too low to go into the second membrane. It you use two 99% rejection membrane in series then you only keep 1/10000 of the volume you put through your RO filter. ( rejected 99% of the 1 % that go through the first membrane)

However I’d you use the 500 instead of the 800ml/min then your rejection rate going to be a lot less. This is the problem in your case.