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Waiting for RODI


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Wanting to fill up the new tank but have to wait for rodi. Painful. Lol. Like watching paint dry. I just need a 100 gallons. Looks like this will take a couple days. They need to come out with a faster way of making rodi. Mini rant over. Lol

 

 

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It's the worst.  

 

I predict floods in your future, though, if you don't get an auto-shutoff float valve.  

 

It will seem like it will never fill and then you'll forget about it and it will suddenly seem like it's flying out when it's going on your floor. 8)

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+1

 

Upgrading your RODI is definitely money well spent. Piggy 100gpd backed RO's and dual DI is some of the best money I have spent. 3a68159f504b149a16f061ddd45f6279.jpg

 

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It's the worst.  

 

I predict floods in your future, though, if you don't get an auto-shutoff float valve.  

 

It will seem like it will never fill and then you'll forget about it and it will suddenly seem like it's flying out when it's going on your floor. 8)

 

I only flooded the basement floor twice last week while making RO/DI! 

 

I need to set up a float switch on my water containers....

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It's the worst.  

 

I predict floods in your future, though, if you don't get an auto-shutoff float valve.  

 

It will seem like it will never fill and then you'll forget about it and it will suddenly seem like it's flying out when it's going on your floor. 8)

 

100 times over this. 

 

Get a float valve. 

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Oh I've flooded my kitchen too many times to count. I set a timer on my phone now everytime I'm filling up if not I'm flooding my kitchen. lol I'll have to look into a float valve.

add a booster pump and upgrade your rodi unit to a 150 GPD or more. 

I'm almost at 80 psi would a booster pump still be useful. I'll probably get 150 membrane next time.

 

+1

Upgrading your RODI is definitely money well spent. Piggy 100gpd backed RO's and dual DI is some of the best money I have spent. 3a68159f504b149a16f061ddd45f6279.jpg

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Nice setup. I'll have to look into that. My RODI is under my kitchen sink so space is limited for me.

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.

I'm almost at 80 psi would a booster pump still be useful. I'll probably get 150 membrane next time.

If you have 80psi I would not see the reason for needing a booster pump. What is your current membranes gps? Adding a second RO may be the way to go as waiting for your current RO to die out and needing to be replaced may be a while. My 100gpd membranes which have been in use for over 4 years still puts out 1-2 tds water and I have no intention to replace them anytime soon.

Also, piggybacking membranes will save you water as the waste water coming out of the 1st membrane is the supply to the 2nd membrane.

 

 

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If you have 80psi I would not see the reason for needing a booster pump. What is your current membranes gps? Adding a second RO may be the way to go as waiting for your current RO to die out and needing to be replaced may be a while. My 100gpd membranes which have been in use for over 4 years still puts out 1-2 tds water and I have no intention to replace them anytime soon.

Also, piggybacking membranes will save you water as the waste water coming out of the 1st membrane is the supply to the 2nd membrane.

 

 

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Yeah that’s what I figured. I forgot these membranes last a while. I have a 100 gpd which is less than a year old. I think I can squeeze another membrane into my setup. Saving water would be good as my water bill has almost doubled since putting in the rodi. Thanks for the info

 

 

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I upgraded my 75gpd brs rodi to the 150gpd. Being unsure how it would save water even though it runs the waist line though the second ro membrane I timed filling a one gallon jug and measured the waist water before I installed the second membrane. It was a few years ago so I do not remember the exact timing but before I filled one gallon of rodi and 4 gallons of waist in say 45 minutes. Once I installed the additional membrane I filled one gallon of rodi and 4 gallons of waist in about 20 minutes. I never actually saved water, or reduced waist as brs claims. It was the same ratio, just twice as fast.

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(edited)

I upgraded my 75gpd brs rodi to the 150gpd. Being unsure how it would save water even though it runs the waist line though the second ro membrane I timed filling a one gallon jug and measured the waist water before I installed the second membrane. It was a few years ago so I do not remember the exact timing but before I filled one gallon of rodi and 4 gallons of waist in say 45 minutes. Once I installed the additional membrane I filled one gallon of rodi and 4 gallons of waist in about 20 minutes. I never actually saved water, or reduced waist as brs claims. It was the same ratio, just twice as fast.

I am not sure why you are not seeing a reduction in the waste water. When I added my piggyback RO, I was able to increase my output almost double while still producing about the same amount of waste.

It appears that there is something different between how you and I have our filters configured.

 

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Edited by tom39
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Well ended up ordering an additional RO membrane and housing this weekend. Looking forward to making the RODI water faster. Thanks for the info.

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I am not sure why you are not seeing a reduction in the waste water. When I added my piggyback RO, I was able to increase my output almost double while still producing about the same amount of waste.

It appears that there is something different between how you and I have our filters configured.

 

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I see the same.  I seem to get the same amount of water out of my waste, but double the RO/DI output, so in effect the waste was cut in half.

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According to BRS, if the membranes are hooked up in series, expect to the same amount of waste but double RODI product. However, the membranes may need to be replaced more often, if the tap TDS is too high.  

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e0d2256add2026abebb6874430b2adcc.jpg

 

Wanting to fill up the new tank but have to wait for rodi. Painful. Lol. Like watching paint dry. I just need a 100 gallons. Looks like this will take a couple days. They need to come out with a faster way of making rodi. Mini rant over. Lol

 

 

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If there is nothing in the tank yet, you can save yourself some trouble by filling and mixing directly in there.

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If there is nothing in the tank yet, you can save yourself some trouble by filling and mixing directly in there.

My RODI was too far away to directly fill it, if not thats probably the route I would of gone. Well all filled up now. Need to do some aquascaping and get my lights mounted and I'm good to go.

 

 

I saw this video of the RO upgrade. Looks like he was getting less rejection water. Well parts ordered so I'll let you know how it all works out.

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My RODI was too far away to directly fill it, if not thats probably the route I would of gone. Well all filled up now. Need to do some aquascaping and get my lights mounted and I'm good to go.

 

 

I saw this video of the RO upgrade. Looks like he was getting less rejection water. Well parts ordered so I'll let you know how it all works out.

Looking at the BRS kit, I noticed that it doesn't change out the flow restrictor for one that is more appropriately sized for 150 gpd. Instead, the (550 ml/min) restrictor on his system is what BRS sells for a 75 gpd system and that most others will sell for a 50 gpd membrane.

 

The waste water is reduced because the restrictor in this setup is sized for a single membrane and the RO membrane surface area has been doubled with the addition of the second membrane. 

 

Here's some of the problem with this setup (and, consequently, of the BRS kit): The whole idea behind a flow restrictor is to create pressure on the membrane (to force water through it while blocking dissolved solids) while maintaining a flow of waste water past the membrane to flush the impurities out. In other words, the so-called "waste water" is better described as "flush water." This flow keeps the membrane cleaner helping it to last longer. By using undersized restrictors and by not including a larger restrictor in their upgrade kit, the membranes in this setup will deteriorate more quickly and need replacing more often. The kit should have come with at least an 1100 ml/min flow restrictor - even that's undersized (calculations using the manufacturer specs say it might be closer to 2000 ml/min).

 

These Filmtec membranes spec sheet lists a recovery rate of 15% - implying that the restrictor should be sized so that you have a waste of 5x the permeate (pure) water out. So, 1 gallon of RO produces 5 gallons of flush water. More typically, though, RO/DI suppliers size the restrictor so that 1 gallon of RO produces 4 gallons of waste - a 20% recovery rate - for a 75 gpd system. It helps to reduce waste a little at a slightly shorter life for the membrane. However, what you see here is a 150 gpd setup with a restrictor that's more typical of a 50 gpd system and more probably matched to 40 gpd production. While he'll have less waste water, he'll be replacing those (expensive) membranes more often. 

 

BTW, it appears that BRS uses undersized flow restrictors across the board. I haven't a clue as to why they're doing that. It may appear to be more efficient, until you factor in membrane replacement costs.

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If you have more interest in flow restrictors, here's a nice sheet from Axeon (manufacturers of the 150 gpd membrane). It shows which flow restrictors map to what membranes. 

 

Note that the 525 ml/min restrictor is recommended for the 50 gpd membrane; 735 ml/min for a 75 gpd membrane; and 1577 ml/min for a 150 gpd membrane.

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I used the dual membranes in series with a single 4:1 restrictor for many years and very happy with the result. 

Here is the BRS investigate video comparing the single 75GPD vs dual in parallel and dual in series.

Would have love to see the result of a SINGLE 150 membrane in the comparison.

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Here's a good post (at Reef Central) by Russ from Buckeye Hydro where he explains the importance of properly sizing the flow restrictor to optimizing the membrane's performance and lifetime. As a hobbyist, you're less likely to notice that your membrane is degrading faster since it happens over a long period. You're more likely to notice that your waste flow is decreasing, though. You have to factor the cost of replacing the $35 membrane with an average cost of $2-$3 per 1000 gallons for municipal water. Russ was/is a long-recognized RO/DI expert from the industry over at RC and has done a lot over the years to help people understand how RO/DI systems work and are constructed. (He's occasionally posted here, I believe.) I that's a valuable service that he's given to the community. We invest so much time learning about other aspects of our hobby. Why  not understand the "black magic" of our RO/DI system - a central component of many of our setups?

 

Chuck, if you're using the 4:1 restrictor that was originally sized for 1 membrane, it's no longer functioning as a 4:1 restrictor for a dual membrane setup. It's effectively become a 1.78:1 restrictor, which further concentrates the waste in the second membrane and reduces the flush water. Here's how I arrive at that conclusion (by my calculation):

 

If you have 5 units of water coming into the first membrane, this is divided into 1 unit of pure water and 4 units of waste water. (Note, the waste water TDS in now about 120% of the source TDS.) In the second membrane, you've got 4 units coming in and that's divided into 4/5 unit of pure water and 3-1/5 units of waste water. The total waste water is 3-1/5 units and the pure water is 1-4/5 units. The waste-to-pure ratio is 1.78. To maintain a true 4:1 ratio, you have to increase the size of the restrictor to 1577 ml/minute for two 75 gpd membranes in series. It really doesn't matter if it's two 75 gpd membranes in series or a 150 gpd membrane. The calculations are the same. In many cases, though, our sources don't routinely carry a 1577 ml/min flow restrictor - they more commonly carry 550, 800 and 1100 ml/min restrictors. That's why places like AirWaterIce.com (a WAMAS sponsor) stocks the 1100 ml/min fast-flush restrictor. If you wanted, you could pair up the 150 gpd membrane with BRS's 550 ml/min restrictor and have it behave just like the two 75 gpd series membranes, except at a lower replacement cost - one $60 membrane vs two $35 membranes. Ideally, though, you match the 150 gpd membrane up with the right flow restrictor so you're investment lasts longer.

 

Remember, the whole idea behind reverse osmosis is to use pressure to push tiny water molecules through a semi-permeable membrane that allows the water to pass, but not the  larger stuff. Conceptually, it's a mechanical filtering process, just on a microscopic scale. And, just like other mechanical filters, the pores can clog. Furthermore, as dissolved solids concentrate in the waste water, they can begin to precipitate and form films (Russ calls it "scale") that clog the membrane. Over the long haul, as the pores clog or are blocked, the pure water recovery rate drops off and production drops because it's now taking forever to make a gallon of water.  At that point you have no choice but to replace the membrane. That's how and why flushing becomes important to extending the membrane life. The so-called "waste-water" is not really a waste. It serves a valuable purpose. If we were only concerned with reducing the waste water, we could install arbitrarily smaller restrictors and not mess with installing a second membrane. (Russ makes that point, too.) The reason that we don't is because it reduces the membrane life.

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