Head Swimming about RO/DI
- Thread starter DSDoyle
- Start date
Buckeye Hydro
.Registered Member
REJECTION: The percentage of TDS that is sent to the concentrate (waste water). The higher the rejection rate, the more pure the permeate (RO water). Rejection is calculated like this: (Feedwater TDS-Permeate TDS)/Feedwater TDS
This equation will yield a number something like 0.94 -> that's a 94% rejection rate
RECOVERY: The percentage of the feedwater recovered as permeate. In this hobby, for some reason, people perfer to think of this as the waste water volume compared to the permeate volume - such as the proverbial 4:1 ratio. The 4:1 ratio is a (1/5=0.20) 20% recovery.
And yep - that $4 part is the flow restrictor.
Russ
This equation will yield a number something like 0.94 -> that's a 94% rejection rate
RECOVERY: The percentage of the feedwater recovered as permeate. In this hobby, for some reason, people perfer to think of this as the waste water volume compared to the permeate volume - such as the proverbial 4:1 ratio. The 4:1 ratio is a (1/5=0.20) 20% recovery.
And yep - that $4 part is the flow restrictor.
Russ
homer1475
New member
This is kind of what I was thinking(in more laymans terms though).
Thanks for the clarification. :thumbsup:
You know, its nice to have people on these board that are experts in their fields and can explain in detail what is what.
Buckeye Hydro
.Registered Member
Glad to help!
Russ
Russ
Buckeye Hydro
.Registered Member
Unfortunately there is a popular pet supplies vendor who has people thinking they need to add a second membrane plumbed in series to cut down on their waste water.
No need to add a membrane - just change your $4 flow restrictor.
Russ
CStrickland
New member
Good stuff. Thanks Russ!
Dundermifflin
New member
Why create such a headache for yourself. For $200 you can get a 150GPD value saver plus from BRS that comes with everything you need. I have this unit and it works great. Flushing the unit is no big deal at all. They even tell you it doesn't need to be done every time. I don't run this unit 24/7. I simply turn it on when I need water. It fills it up quickly and I have no issues at all. I have mine connected to an outside hose bib. I run the line about 40' into the house and 8' up the wall and get perfect pressure without any booster pump. You will be very happy with this purchase.
CStrickland
New member
Why wouldn't you need to do it every time?
dabob79
New member
Russ, could you please elaborate on this? I've just set up my first large tank and have the BRS 75 gpd unit. I'm fairly new to this so I'm not familiar with the flow restrictor. Am I dumping more water down the drain than I need to? Thanks!
Bob
shifty51008
12-5 Chiefs record
A membrane suggests you want 4:1 waste to good this is to keep the membrane from clogging up to fast. I think by cutting down your waste water you kill the membrane sooner so will have to be changed more often than normal.
Buckeye Hydro
.Registered Member
Shifty has it.
The recommended 4:1 ratio comes from the membrane manufacturers. If you want to go lower than that, say to a 2:1, you can do that by changing that $4 flow restrictor, but realize you would likely be shortening the usable life of your membrane. You may be ok at a 2:1 if you have softened water with no complicating water constituents.
If you live in CA in that drought, that may be a reasonable tradeoff.
Russ
The recommended 4:1 ratio comes from the membrane manufacturers. If you want to go lower than that, say to a 2:1, you can do that by changing that $4 flow restrictor, but realize you would likely be shortening the usable life of your membrane. You may be ok at a 2:1 if you have softened water with no complicating water constituents.
If you live in CA in that drought, that may be a reasonable tradeoff.
Russ
Jlentz
New member
Ok. Thanks buckeye. So on the brs 75 gpd unit what exact flow restrictor do I need?
If I got another membrane on top of that would it further decrease the waste water or is it pointless?
Buckeye Hydro
.Registered Member
No need for it. Use a restrictor that gives you a ratio near 4:1.
gone fishin
New member
I would just like to thank Russ for taking the time to explain these things not just here but on other threads as well. :beer:
Buckeye Hydro
.Registered Member
:beer:
shifty51008
12-5 Chiefs record
I couldnt agree more, russ and all their go above and beyond to satisfy their customers and even help others out even if their unit isnt from them. That is what made me a costomer of theirs for replacement parts and filters, their maxro membrane cant be beat imo, i love it.
A toast to russ and the crew. "Here, Here"
Thankyou
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