DIY RO Filter - Flow restrictor sizing & pure to waste ratio

[newfly]

I'm thinking to buy the component individually.

I am interested in Dual 100gpd DOW Filmtec membrane in a series ( waste from membrane 1 feed into membrane 2).

Incoming water pressure is 65psi, ~260ppm

What size flow restrictor do i need? I believe i just need to restrict the flow for the membrane 2 waste line. Is this correct? I'm guessing i need 550cc size?

How do i calculate the Pure to Waste ratio? I don't think number of stages (sediment, carbon, etc) matter for this. I'm hoping to get at least 1:1. Some system claimed 1.5:1 or even 2:1. Is this because they use boaster pump to increase the incoming psi?

 

[H2OPlayar]

How do i calculate the Pure to Waste ratio? I don't think number of stages (sediment, carbon, etc) matter for this. I'm hoping to get at least 1:1. Some system claimed 1.5:1 or even 2:1. Is this because they use boaster pump to increase the incoming psi?

Get two of the same buckets, and a scale. Measure the low bucket when the other one fills up.

Usually the higher # is the waste, not the product water.

 

[richiev]

RE getting numbers higher, my understanding is booster pump is for sure a key part of that, as can things like water temp help. Exact targets I think the membranes say. However at some point the more you push through, the more you have things pass through, which then get caught by your DI. Reduces waste, but trades waste water for resin replacement.

RE membrane's connected, I do that, but TBH I've never actually understood how that could truly reduce overall waste. It does lead to requiring less water to be used, but it ends up being:

(made up numbers)

15 units of water
           |
           |
           |
first membrane ==output=> 5 units of pretty pure water to DI ===> pure water
           |
           |
      10 units of high TDS water
           |
           |
second membrane ==output=> 3 units of pretty pure water to DI ===> pure water
           |
           |
      7 units of really high TDS water

That looks like it's reducing overall waste, but:

• it'll burn through that second membrane faster than normal, because it's feeding high TDS water to it
• because of the higher TDS, it'll also burn through more resin b/c the output of the second membrane is likely higher than the first one
• each membrane is going to add some backpressure, which I'm not an expert in, but likely makes each membrane perform worse

It seems like it should be better, but it's not like people are getting free extra water out of this system, and I'm not intuitively clear if it's better than just having two membranes in parallel. It seems like it'd be some sort of differential equation to really calculate it.

Is it better to just run a booster pump + parallel membranes + use the waste water to do something productive (water plants)?

 

[newfly]

Thanks!

Can someone help me sizing the flow restrictor?

 

[H2OPlayar]

Thanks!

Can someone help me sizing the flow restrictor?

Reverse Osmosis Flow Restrictor

Flow restrictors are essential to a properly functioning RO system. Be sure to have the appropriate flow restrictor for the membrane you have. If you decide to change your membrane to a higher or lower GPD membrane, you must also replace the flow restrictor to correspond with the membrane. All...

www.bulkreefsupply.com

 

[newfly]

Reverse Osmosis Flow Restrictor

Flow restrictors are essential to a properly functioning RO system. Be sure to have the appropriate flow restrictor for the membrane you have. If you decide to change your membrane to a higher or lower GPD membrane, you must also replace the flow restrictor to correspond with the membrane. All...

www.bulkreefsupply.com

View attachment 69961

I saw that, but for 2x 100gpd membrane in series , should I size it for 100gpd , 150gpd or 200gpd?

 

[H2OPlayar]

I am pretty sure you should just get the booster pump and the auto flow restrictor below. Check out the chart below for the "water saver" configuration. Copy my setup below.

1/4" Aquatec 8800 RODI Booster Pump Kit

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1/4" 8800 Booster Pump Kit

Boost Your RO/DI System's Performance Solves Low Pressure Problems: Ideal for RO/DI systems needing a pressure increase. Complete Solution: Includes all necessary components for a quick setup. Enhanced Efficiency: Improves waste water ratio and membrane performance. Noise-Reducing Design...

www.bulkreefsupply.com

Auto Flush Flow Restrictor

Choose the Aquatec Auto Flush Flow Retrictor that meets your RODI systems flow rate. 300 mL/min 400 mL/min 500 mL/min for 75 GPD single membranes or 150 GPD Water Saver Systems 600 mL/min 700 mL/min 800 mL/min for 100 & 150 GPD single membranes or 200 GPD Water Saver Systems The Aquatec...

www.bulkreefsupply.com

 

[Coral reefer]

I’ve never used the auto flush, seems cool but also kit needed if you aren’t making tons of water constantly for long periods imo.
I disagree with @richiev s logic.
I use membranes in series to reduce waste. Yes it works. I have 3 membranes and get 1:1 waste to product.
Membranes 2 and 3 probably get used up faster, and Di might get used a little faster but not much.
Depends on source water for sure.
Yes you need high pressure or the pump to make it work right.
He didn’t mention the cost savings if the ordikters which is what I spend the most money on. You get more product water for the useable life of the carbon blocks. They get used up by waste water too.
Also saving water is my primary goal.
Membranes need to waste 3-4:1 to work properly. They need the waste to carry away the stuff he membrane is rejecting.
Should reject 98%. You can Nath it out how much that concentrates the water for the next membrane pretty easy, and for the product out of the next membrane too.
Start with 300 tds get 6 out of membrane 1.
I think you send 400ish tds to next membrane. Should get 8 out