RO/DI filter flow restictor question

mike660r

mike660r

New member
I am planning on pairing two RO membranes to make a larger output system. I believe both membranes are 75 GPD units. How do you know which flow restrictor to use? I have two different types because I am joining two different RO setups together. One of the restricters has a long tube on it and the other has a short one. When going to larger output RO systems what is the preferred restricter to have?
 
I wasn't aware that you could use both membranes, after one filters out the bad water, then why would you re filter the good output again? once the RO membrane takes out the bad stuff, what would be the purpose of running it through another membrane to create more waste water?
I thought you were going to use one high ouput membrane, such as 150 gpd and use the canisters only on the second unit for extra sediment, and carbon.
Erik
 
I think you could tee them off of the supply line and use both of them to each filter their rated quantity of water therefore giving you more RO output. I do not know if you can run them into the same DI cartridge to get the last of the ions out.

If it were done this way then you would need both restrictors.

I have never researched this. I am just going off what seems logical to me.

Hope that helps,
-- Kevin

Here's a pic of what I thought you would do with 2 RO membranes.
 
Last edited:
Mike,

I agree with Erik that you don't want to run them in series; ie. one output into the other.

However, I think the way you described it your really looking to run the RO membranes in parallel. In other words, the output from the one sediment and charcoal runs to a T that feeds the two RO membranes. So you will have one input into each membrane and two outputs for each membrane (4 total). Two of the outputs are waste and two are RO. To set the restrictors you will need to compare the waste from one membrane to the product of the same membrane(I believe Spectrapure is 4:1). Do not T the wastes or the outputs from the two RO membranes; run four seperate output lines. As a side note: the lines from the T leading into each RO membrane should be the same length to keep input pressures balance ( only a subtle detail as long as you leave things the same once you adjust the flow restrictors).

Of course, the presumption is that the RO membranes are the 'slow' point or restriction in the system. If the sediment and charcoal filters limit the flow, running the two membranes in parallel will not increase the output. I suspect your system will see a big increase in RO production but not quite the sum of the two rated outputs.

Hope this helps.

Dave
 
Kevin's reply had not posted...... If you are running both RO outputs through a single or separate DI cartridges I doubt you would be able to balance the system....... in other words you could end up with 75 through one membrane and 20 the other. Worse yet; you could end up with 90 'not so pure' through one RO and 20 through the other.

Just some thoughts

-Dave
 
i have a dual membrane spectrapure and it has the waste from membrane 1 going to membrane 2. then both product lines are merged into a t. spectrapure site has some manuals
 
Thanks everyone, the information posted here did answer a few more questions for me. However, I am still baffled on which restrictor to use. I do plan to have 1 sediment, 1 carbon and 3 DI canisters set up. I also plan to feed the unit in the same manner in which the spectrapure unit is set up in the link above. I need to know how to determine which restictor to insert.

Rizing, what is your GPD rating on your system? Is it a 200?
 
mike660r,
Both flow restrictors should be the same. I don't know which is which, but they should be the same. Flow restrictors essentially cause back pressure forcing water through the membrane. You might want to grab two new restrictors for a 75 GPD to be sure. They are pretty in expensive. You could also try Russ at BFS.
 
They run about 3-5 bucks and they do come in different rated sizes. That's what makes me question the whole topic.
 
Mike,
If you mispair the flow restrictor two things can happen.
1) not enough 'restricting" = lower product water volume and mor waste water.
2) too much restriction = shorter membrane life. Typically, r/o makers match the proper restrictor to their membranes. You might want to start with the original maker. *caution* if you bought these used...many hobbiest don't understand the fuction of the restrictor. They will by a 20 GPD unit and ad a 75 GPD membrane without giving thought to the restrictor.

You could call BFS and ask them the lenght of the "tail" on their 75 restrictor. Then, you could match it to the correct one of yours.

Good Luck
 
There's a chart in the inctructions that gives the lengths the restrictors are supposed to be based on the GPD the unit is rated for.
 
<a href=showthread.php?s=&postid=10862024#post10862024 target=_blank>Originally posted</a> by mike660r
Now thats a novel idea!
Click to expand...

novel...
Would be a pretty short book wouldn't it? Not much romance to flow restrictors either IMO.

If you put Fabio on the cover it will prolly still sell...

mikesnewbook.jpg


Man I gotta get back to work soon :)
 
Mike,

The setup Rizing pointed you to in the Spectrapure manual is for two RO membranes that have the same output; that is how they can run them in series with only one flow restrictor at the final waste output. In that case you would use the flow restricter that matches the individual membrane output.

I'm not clear if your using two identical membranes but you can easily swap one out so they are matched...... I know Salty C usually has membranes and flow restrictors (the adjustable sound like the best though).

Last comment for anyone tagging along that may not know; when I upsized my last RO membrane I spent a few extra bucks for the one tested by Spectrapure to have 98 percent plus removal. My TDS measurements of the output are usually at 2 where I had been in the 14-17 range. It has really helped to prolong the life of my DI resins.

-Dave
 
<a href=showthread.php?s=&postid=10862085#post10862085 target=_blank>Originally posted</a> by scottfarcuz
novel...
Would be a pretty short book wouldn't it? Not much romance to flow restrictors either IMO.

If you put Fabio on the cover it will prolly still sell...

mikesnewbook.jpg


Man I gotta get back to work soon :)
Click to expand...

You must still be ill bro... :rollface:

I got a really good laugh out of that one.
 
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