Spotlight on the BRS 150GPD Upgrade Kit | BRStv

[randyBRS]

Hey guys!

Today we're revisiting the BRS 150GPD Upgrade Kit where we talk about what it can do for you and how to get one installed. On top of that, today we've got them on sale!

 

[Brew12]

I had no idea these existed! I can't watch the video right now but I want to make sure I understand this correctly.

I have this

and this

So I can get this upgrade kit and turn my current system into a high efficiency 150gpd system?

 

[Whipples]

I had no idea these existed! I can't watch the video right now but I want to make sure I understand this correctly.

I have this

and this

So I can get this upgrade kit and turn my current system into a high efficiency 150gpd system?

Those would all help improve production and efficiency of the membranes, but the waste ratio is the same (3-4:1) as it would be with a single membrane, you are just adding a second output of RO water into your DI media. Going lower than 3:1 waste to product water ratio will lead to premature failure of the membrane, especially if TDS is > 200, if you have chloramines, etc.

I run a dual membrane and booster because it allows me to make more water in the same timeframe, allowing me to enjoy the tank more, but not because it lowers the waste ratio inherent with most RO systems.

 

[Brew12]

Those would all help improve production and efficiency of the membranes, but the waste ratio is the same (3-4:1) as it would be with a single membrane, you are just adding a second output of RO water into your DI media. Going lower than 3:1 waste to product water ratio will lead to premature failure of the membrane, especially if TDS is > 200, if you have chloramines, etc.

I run a dual membrane and booster because it allows me to make more water in the same timeframe, allowing me to enjoy the tank more, but not because it lowers the waste ratio inherent with most RO systems.

Maybe I am missing something but I don't think that is how this works. The output of the 75gpd membrane still goes to the clean water. The rejected water goes through the second membrane where it gets processed again. So the output of the 2nd filter would be added to the old output of the original filter.

 

[Whipples]

@Brew12 correct, brine output from membrane one is input to membrane 2, so that second membrane gets hit with 25% or so more tds than the first which is why PSI is important. That first membrane is still functioning at 3-4:1 ratio, and so is the second.

 

[Brew12]

@Brew12 correct, brine output from membrane one is input to membrane 2, so that second membrane gets hit with 25% or so more tds than the first which is why PSI is important. That first membrane is still functioning at 3-4:1 ratio, and so is the second.

Fantastic, that is what I thought.... so time for some math....;Writing

And as I did the math I realized something. The 2nd filter cannot have both the same rejection rate and the same throughput as the first filter. The added filter must have higher throughput for a given rejection rate.

If the first filter is making 100g and rejecting 400g then that 400g is going to the second filter. If it also has a 100g throughput in that period of time it would only have 300g available to reject. If this is accurate and is splits the load fairly evenly, then the 2nd filter much have a much more efficient design since it is rejecting less to process dirtier water. So our total rejection on the first one is 4:1 and the second one is 3:1 ;Bookworm. Since that total of 500g of water (4:1) is now making 200g we have gone from 4:1 to 3:2 which is way more efficient. ;Singing

I thought this was going to be simple. It probably would have been but my margarita seems to be evaporating next to me.

 

[Whipples]

Pretty close! One thing the math doesn’t account for is setting the flow restrictor based on your source water quality and important for maintaining a healthy membrane. In series you run the first membrane without a restrictor on the brine output into the second membrane, and the second membrane has the restrictor on what is now the “final” brine output. You still set that capillary restrictor based on the desired waste ratio because not all water is created equal and not everyone runs identical PSI and temperature, etc. but what we can control is flow rate through the membrane.

So assuming you set your flow restrictor appropriately, you would still be making 4 gallons of “waste” to one gallon of “product water out of the entire unit because you cut the capillary style restrictor length based on what product water output you have measured over a minute. Waste is the same, just somewhere between 1.5 and 2x as fast as before. They operate in a series and both membranes are effectively controlled by that final flow restrictor since they share a common output, and to your point not exactly the same output individually. Flow through both membranes is not exactly equal, but the total water produced compared to wasted is still the overall ratio set by the restrictor since we aren’t measuring after each membrane but their combined output of product water.

I run a dual membrane because I’m impatient and use a booster for 93psi to get 98% ish rejection and run the waste line into my top-loader washer (I’m also cheap, and would prefer to use the water I pay for). When I fill my ATO to 10 gallons, that gets me 30 gallons of water in my top loader (40g ish capacity) because I set my flow restrictor at 3:1, and is enough for a decent size load of laundry. TDS at the source for me is ~200, brine output into the second membrane is about ~250-270, and product water from both is about ~4 TDS before it goes into the DI media. It takes about 7 minutes to make a gallon using this setup.

 

[Brew12]

They operate in a series and both membranes are effectively controlled by that final flow restrictor since they share a common output, and to your point not exactly the same output individually.

Except that they don't operate in true series. The new one is in series with the waste water of the first one. The flow restrictor is on the waste water output of the second one which I believe is done to maintain pressure in both units. The clean water outputs of the two are in parallel.

Obviously, I'm not a RODI expert and I am missing something. I assumed a dual membrane unit like yours had the input water in parallel and the reject water in parallel being combined to share the flow restrictor. The clean water would then be sent through the rest of the filter.

Guess I need to do more homework.

 

[Whipples]

@Brew12 That may be one way to run it that I haven't thought of or tried before. I know I run mine as source water -> carbon & sediment blocks -> first membrane -> second membrane -> DI media, where the waste line output of membrane #1 becomes input water to membrane #2, and both the product water lines get joined up in a parallel fashion and fed into the DI media via Y connector. I am by no means a physicist or plumber but given the measurements of product and waste that is how I understand it and experienced it.

 

[Brew12]

@Brew12 That may be one way to run it that I haven't thought of or tried before. I know I run mine as source water -> carbon & sediment blocks -> first membrane -> second membrane -> DI media, where the waste line output of membrane #1 becomes input water to membrane #2, and both the product water lines get joined up in a parallel fashion and fed into the DI media via Y connector. I am by no means a physicist or plumber but given the measurements of product and waste that is how I understand it and experienced it.

Obviously, I'm not either! I really do appreciate the insight!

 

[Bulk Reef Supply]

I'll leave the answers to your technical questions to @randyBRS - but here is the actual upgrade kit (currently 10% off): https://www.bulkreefsupply.com/brs-150-gpd-water-saver-upgrade-kit.html

Kit includes:

• Dow 75 GPD membranes
• Two 2.5" x 2.5" membrane clips
• Two 1/8" x ¼" 90 degree elbows
• 1/8" x ¼" 90° check valve
• RO membrane housing
• ¼" tube splitter
• 5 Feet of Red, White, Blue and Black RO Line

Recommended Conditions:

• Minimum Water Pressure - 65 PSI
• Max Water Pressure - 90 PSI
• Recommended Water Temperature - 77°F
• Recommended Max TDS - <300ppm

Water pressure can be increased by adding a booster pump before your RO/DI system if a pressure increase is required. Low pressure will cause slow production of product water, with excess production of waste water. Pressure over 90 PSI may cause damage to the RO/DI units filters and components.


DOW Filmtec 75 GPD Membranes have a 96% - 99% typical stabilized salt rejection rate that can be reproduced through the following conditions;

• Source Water Pressure - 50 PSI / Membrane
• Source Water Temperature - 77°F
• Source Water TDS - 250ppm Softened Tap Water
• Recovery - 15%
• Minimum Salt Rejection - 96%

 

[Ryanbrs]

So most of this is fairly correct but there is a lot of grey area.

Membranes are commonly spec'd at 15% recovery which is approaching 6 to 1 waste to product ratio. I have never seen a system set up that way. A lot of references will say 4:1 but I also haven't seen many higher flow 75-100 GPD residential systems set up 4:1 with 800-1,000ml/min flow restrictors. Fact is, it isn't a perfect science and completely dependent on not just your TDS but also whats in it. For instance, someone's 400 TDS water may perform better at 4:1 but someone with 100 TDS source water may very well get away with 2:1. It also depends on what is in the water, the 400 TDS water might last longer than the 100 if it has been softened and most of the hardness has been replaced with sodium which doesn't scale the same way.

The ratio on your system is pretty easy to figure out. a 75 gallon per day membrane emits ~200 ml a min so 2:1 would be 400 ml of waste/brine a minute. 3:1 would be 600 and 4:1 800. To identify how much waste your system produces you could measure how much waste comes out in a minute or just look at the number on the side of the flow restrictor cylinder which represents ml/min.

Today it is much more common to see 2:1 or 3:1 simply because most people don't want to waste tons of water and today's membranes last a very long time in even the toughest environments. Unless you know you have terrible water I personally suggest running a fairly low ratio and only changing if you find the membrane doesn't last as long as you like or having rejection issues. Almost always makes sense to start low and work up.

There is also pressure to consider. On many residential systems 2:1 or 3:1 might perform better on higher flow residential 75/100 GPD membranes because the lower flow ratios are able to maintain high pressures and pressure is one of the most important performance specs. High pressure almost always = higher flow rates and lower TDS product water.

As to the two membranes in the water saver configuration, there is actually the "more" flush than installed in a normal configuration. Its hard to grasp but this is how it works. Let's say you have 100 TDS source water, 75GPD membrane and want a conservative 2:1 ratio. That would require a 400ml/min flow resistor. Then at a later date you add a water saver dual membrane kit where one feeds off the other. this is what's going to happen in each membrane.

Membrane 1 has 100 TDS feeding it and likely has 98-99% rejection with 1-2 TDS product water. This membrane has no flow restrictor on it and relies on the pressure from the second membrane. The flush ends up being all the water feeding and leaving the second membrane which is 200ml/min product + 400ml/min waste. So membrane 1 has 200ml product and a total of 600ml of waste or flush and an increased ratio of 3:1. So even better than you had before.

Membrane 2 is fed the c0ncentrate /brine/waste of membrane 1 and rather than 100 TDS it is likely now ~130 TDS however with a rejection rate of 98-99% it is going to be the same 1-2 TDS and once the two products are mixed together there is almost no real difference. In this case, the product to waste will be the intended ratio of 2:1 with the 400ml flow resistor and 200ml from the 75 GPD membrane.

Math is slightly different as you scale this up but even if you ran at 5:1 in the second membrane, the first membrane will always have even more flush.

 

[Brew12]

So most of this is fairly correct but there is a lot of grey area.

Membranes are commonly spec'd at 15% recovery which is approaching 6 to 1 waste to product ratio. I have never seen a system set up that way. A lot of references will say 4:1 but I also haven't seen many higher flow 75-100 GPD residential systems set up 4:1 with 800-1,000ml/min flow restrictors. Fact is, it isn't a perfect science and completely dependent on not just your TDS but also whats in it. For instance, someone's 400 TDS water may perform better at 4:1 but someone with 100 TDS source water may very well get away with 2:1. It also depends on what is in the water, the 400 TDS water might last longer than the 100 if it has been softened and most of the hardness has been replaced with sodium which doesn't scale the same way.

The ratio on your system is pretty easy to figure out. a 75 gallon per day membrane emits ~200 ml a min so 2:1 would be 400 ml of waste/brine a minute. 3:1 would be 600 and 4:1 800. To identify how much waste your system produces you could measure how much waste comes out in a minute or just look at the number on the side of the flow restrictor cylinder which represents ml/min.

Today it is much more common to see 2:1 or 3:1 simply because most people don't want to waste tons of water and today's membranes last a very long time in even the toughest environments. Unless you know you have terrible water I personally suggest running a fairly low ratio and only changing if you find the membrane doesn't last as long as you like or having rejection issues. Almost always makes sense to start low and work up.

There is also pressure to consider. On many residential systems 2:1 or 3:1 might perform better on higher flow residential 75/100 GPD membranes because the lower flow ratios are able to maintain high pressures and pressure is one of the most important performance specs. High pressure almost always = higher flow rates and lower TDS product water.

As to the two membranes in the water saver configuration, there is actually the "more" flush than installed in a normal configuration. Its hard to grasp but this is how it works. Let's say you have 100 TDS source water, 75GPD membrane and want a conservative 2:1 ratio. That would require a 400ml/min flow resistor. Then at a later date you add a water saver dual membrane kit where one feeds off the other. this is what's going to happen in each membrane.

Membrane 1 has 100 TDS feeding it and likely has 98-99% rejection with 1-2 TDS product water. This membrane has no flow restrictor on it and relies on the pressure from the second membrane. The flush ends up being all the water feeding and leaving the second membrane which is 200ml/min product + 400ml/min waste. So membrane 1 has 200ml product and a total of 600ml of waste or flush and an increased ratio of 3:1. So even better than you had before.

Membrane 2 is fed the c0ncentrate /brine/waste of membrane 1 and rather than 100 TDS it is likely now ~130 TDS however with a rejection rate of 98-99% it is going to be the same 1-2 TDS and once the two products are mixed together there is almost no real difference. In this case, the product to waste will be the intended ratio of 2:1 with the 400ml flow resistor and 200ml from the 75 GPD membrane.

Math is slightly different as you scale this up but even if you ran at 5:1 in the second membrane, the first membrane will always have even more flush.

Great info, thanks for the explanation! I'm going to pick one of these things up. I also think when it comes to RODI systems I'll stick with the margaritas over the math.