RODI experts: Booster pump install on Dual purpose RODI system

cgripp256

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So, I have an Express Water 50 GPD RO system installed under my kitchen sink.
38F2FB17-8C5C-4C6E-B114-4B91FF056F89.jpeg


When I began my saltwater journey with a 32 gallon Biocube I realized I could probably just add a DI cartridge to my existing system and have a dual purpose unit. I don't make RODI water for the aquarium automatically. I manually direct water through the DI and into 5 gallon jugs a few times a week and this works fine for me as I usually store them and make 30 gallons of saltwater at a time.

However, I recently added a 3 probe TDS meter and pressure gauge and realized that 1) my incoming pressure is around 50-55 psi and my TDS is 450 (incoming) 30 (post RO) and 2 (post DI). I am pretty sure my DI was 0 initially and I have only made about 50 gallons of RODI water.

I have the DI cartridge connected to the yellow line to the pressurized reservoir tank with a ball valve on the DI side to turn it on and off. When this valve is closed to the DI cartridge the RO water is stored into the tank and when needed it feeds into a carbon filter and then an Alk filter and out a drinking water tap at the sink. When it is open it pushes water from the tank initially, out the DI and then once the tank is depleted, from the RO membrane directly to the DI (Noticeable flow decrease)

Im not sure if Im getting any backflow from the carbon and alk at the end of the chain or bypass to the tank though.

I am looking at adding the aquatic life RO buddy booster pump to my system to improve the incoming pressure and hopefully increase efficiency. All the diagrams I have seen show it used for a single purpose RODI system.

Are there any gotchas to installing this with my setup? For instance, should I install any check valves anywhere? And could I just swap to a higher production rated RO membrane (100gpd to match the max of the pump unit). And would this speed my production when I do go to make DI water after the initial tank water empties.

Thanks!
 

JoshH

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Honestly, purchasing a better membrane would get you further along than a booster pump. Your current membrane is only rejecting 93ish % and more pressure might help a touch, but nowhere near as good as a high quality membrane will.
 
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cgripp256

cgripp256

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You do want a check valve

1652988303242.png
Thanks! Do you concur that a better membrane would be a wiser choice than a booster? And if so any recommendations?

The above diagram is exactly my current setup minus the check valves. And given that I currently see 2 TDS after DI should I change the resin as well? It is color changing and shows no change yet.
 

outhouse

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Do you concur that a better membrane would be a wiser choice than a booster? And if so any recommendations?
No if you have a 75g they tend to do the best job over a 100 membrane. As far as a booster pump, yes you should use one, I had similar pressure and have been over a decade with teh 8800 unit. get that exact one and you will thank me later. another trick you can try is different restriction amounts, I like to tune my system. The other reply correct you want multiple check valves.
 
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cgripp256

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No if you have a 75g they tend to do the best job over a 100 membrane. As far as a booster pump, yes you should use one, I had similar pressure and have been over a decade with teh 8800 unit. get that exact one and you will thank me later. another trick you can try is different restriction amounts, I like to tune my system. The other reply correct you want multiple check valves.
I have a 50 gpd.
 

KStatefan

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Thanks! Do you concur that a better membrane would be a wiser choice than a booster? And if so any recommendations?

The above diagram is exactly my current setup minus the check valves. And given that I currently see 2 TDS after DI should I change the resin as well? It is color changing and shows no change yet.

I would start with a membrane. Your is not rejecting enough as @JoshH said. With the changes Dupont has been making in their membranes I think the Filmtec TW30-1812-50HR membrane is currently the best one. This membrane is speced at 99% stabalized salt rejection at 50 psi and 77° F. You wont get all the way to 99% with has high as your source TDS is but if you got to 97% it would double your resin life. If you want more a booster pump would increase production rate and rejection rate. I have been running this membrane since Aug of last year. I have been recording data each month after running the system for 30 minutes see chart below. After I have a year of data I plan on purchasing a new SpectraPure SpectraSelect Plus membrane and do the same test for a year.

1653046452628.png
 
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cgripp256

cgripp256

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I would start with a membrane. Your is not rejecting enough as @JoshH said. With the changes Dupont has been making in their membranes I think the Filmtec TW30-1812-50HR membrane is currently the best one. This membrane is speced at 99% stabalized salt rejection at 50 psi and 77° F. You wont get all the way to 99% with has high as your source TDS is but if you got to 97% it would double your resin life. If you want more a booster pump would increase production rate and rejection rate. I have been running this membrane since Aug of last year. I have been recording data each month after running the system for 30 minutes see chart below. After I have a year of data I plan on purchasing a new SpectraPure SpectraSelect Plus membrane and do the same test for a year.

1653046452628.png
Wow. I take it you’re in the business :) I appreciate the guidance and advice and will source that membrane today.

Is there any downside to adding a booster? I don’t mind the minor investment if it helps even a little.
 
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cgripp256

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Also, I’m at 3 months of use and I know that the manufacturer recommends a 6 month or 1 year replacement cycle depending on which filter in the system.

Do you have a better way of determining when to replace the pre and post filters? Time seems so “one size fits all” and not very accurate.
 

YOYOYOReefer

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both good suggestions better membrand and the ro buddy is a good choice. I got one about a year ago its been super solid. Ive had home made booster/backflush setups and spent more to make similar.
ive left mine running for 3 days straight at the longest and it didnt break.
 

KStatefan

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Wow. I take it you’re in the business :) I appreciate the guidance and advice and will source that membrane today.

Is there any downside to adding a booster? I don’t mind the minor investment if it helps even a little.

I am not in the business just have to make 0tds water at work and have done some research.

The only downside I see is cost. If I did not have high water pressure I would have a booster pump.
 

redfishbluefish

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Agree with what @KStatefan posted above of the Buckeye Hydro diagram with a slight variation. I'm not a fan of check valves, so instead of the Tee right before the check valve, I'd use a Three way valve (BRS sells them):

BRS Three Way Valve.jpg

With this valve, you're either making tank water or flipping the valve and using it for drinking.

Now I'd do one more thing to save your DI resin. On startup of any RO system you have breakthrough TDS that occurs when the membrane sits unused. It takes a couple minutes of running to clear this breakthrough TDS. So what I'd do is run your drinking water faucet for five minutes to clear the TDS and then flip the valve and start making tank water.

This breakthrough TDS is the reason you don't want to use that reserve tank water to make tank water. It has some level of TDS, and this TDS is what makes the water drinkable (tasteful).

Hope this helps.

And also agree with others....get a membrane that gives you 98%+ rejection.
 
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cgripp256

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I went to make water this morning after emptying about 2 liters of water for coffee making from the drinking tap and got 425 in, 15-20 post RO and 0 post DI. I did shut off the tank first which I normally don’t.

checked again after 45 minutes and 425/14/0

If my math is correct that means I’m getting 96.7% rejection, correct?

I’m guessing those initial results were due to having the tank opened?

also included a pic of my DI resin for reference.

25FEB663-DE2B-4C04-80D0-D9DC91E60AB8.jpeg
 
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cgripp256

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Agree with what @KStatefan posted above of the Buckeye Hydro diagram with a slight variation. I'm not a fan of check valves, so instead of the Tee right before the check valve, I'd use a Three way valve (BRS sells them):

BRS Three Way Valve.jpg

With this valve, you're either making tank water or flipping the valve and using it for drinking.

Now I'd do one more thing to save your DI resin. On startup of any RO system you have breakthrough TDS that occurs when the membrane sits unused. It takes a couple minutes of running to clear this breakthrough TDS. So what I'd do is run your drinking water faucet for five minutes to clear the TDS and then flip the valve and start making tank water.

This breakthrough TDS is the reason you don't want to use that reserve tank water to make tank water. It has some level of TDS, and this TDS is what makes the water drinkable (tasteful).

Hope this helps.

And also agree with others....get a membrane that gives you 98%+ rejection.
If I have a ball valve at the tank and just before my DI isn’t that equivalent to this valve? I know I have to turn two valves on and off but it would work the same, yes?
 
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cgripp256

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I just want to express my appreciation to all who respond and continue to do so. I know it probably gets old answering the same questions but I have really learned a lot from this thread and forum in general.
 

MichaelReefer

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My house has very low water pressure, I was around 30-40 before...got the pump and now Im over 80. Makes a big different once my RODI production.
 

redfishbluefish

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If I have a ball valve at the tank and just before my DI isn’t that equivalent to this valve? I know I have to turn two valves on and off but it would work the same, yes?

Yes that could work as well. But I'm an idiot and I'd forget and either have both valves open or both valves closed. The single three way can't be screwed up. :beaming-face-with-smiling-eyes:
 
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