RO Membrane? for SPS dominate tank

jfingers8

Member
I need to replace my membrane on my ro unit. It's rated for 50 gpd. 2 questions one, does it matter if I buy one that is rated more or less than 50 gpd and two, does it matter what company I go with or is a membrane a membrane? Thanks
 
Not really an SPS question..........

No it doesnt matter if you use a different membrane. Most people consider the dow filmtec 75gpd the best residential membrane. 98% rejection at 50psi, I find it usually does better then this with good new pre-filters.
 
You would need to replace the flow restrictor if you change to a different gph membrane. Its cheap though, a few bucks.
 
Yea so if you buy a 75pgd unit you shouldn't just switch to a membrane rated for 50gpd, you get one that is rated for the unit you purchased.
 
No - that is not what is being said by all the previous posters......You can go up or down in sizing the gpd rate of the new RO membrane *IF* you simply purchase the appropriate flow restrictor (which is a very cheap part - a few dollars at most.)

T
 
I think the best way to restrict the flow is by using a JG ball valve and a PSI gauge right before the membrane. Then you can adjust and set the pressure on the membrane as you watch the guage. This assures you are supplying the right amount of pressure on the membrane.
 
I know I must becoming across like a real hardcase - my apologies, it is not my intent...but NO - the flow restrictor that we are talking about is "downstream" of the membrane, or after it.
The problem with restriction on the up-stream side/ in front of the membrame is that you actually need to increase the pressure on the membrane in order to make it function properly.
That is why you see many guys using "booster pumps" - to increase - not restrict - the pressure to the membrane.
Flow restrictor helps to maintain the elevated pressure in the membrane housing, instead of allowing it to escape downstream

T
 
I know I must becoming across like a real hardcase - my apologies, it is not my intent...but NO - the flow restrictor that we are talking about is "downstream" of the membrane, or after it.
The problem with restriction on the up-stream side/ in front of the membrame is that you actually need to increase the pressure on the membrane in order to make it function properly.
That is why you see many guys using "booster pumps" - to increase - not restrict - the pressure to the membrane.
Flow restrictor helps to maintain the elevated pressure in the membrane housing, instead of allowing it to escape downstream

T

Agree :)
 
What if it is the opposite and you go from a 100gpd down to a 75gpd membrane. Anything need to be changed then?
 
What is a flow restrictor? You should be able to house any GPD type ro membrane in your sytem.If you have decent water pressure from the faucet you can upgrade from 50 GPD to 75 or 90 GPD no problem. They are all universal and drop right in to the membrane housing. Just make sure to buy a good name brand. There are lots of chinese knock offs out there.
 
One more detail. I think the membrane has a built in flow restrictor. This is the hole that lets excess water escape that isnt pushed through the membrane. Take a look at the membrane and you will see what Im describing. The smaller the hole the more GPD the membrane will handle.
 
I know I must becoming across like a real hardcase - my apologies, it is not my intent...but NO - the flow restrictor that we are talking about is "downstream" of the membrane, or after it.
The problem with restriction on the up-stream side/ in front of the membrame is that you actually need to increase the pressure on the membrane in order to make it function properly.
That is why you see many guys using "booster pumps" - to increase - not restrict - the pressure to the membrane.
Flow restrictor helps to maintain the elevated pressure in the membrane housing, instead of allowing it to escape downstream

T

Is that post towards me??

If so I put the ball valve on the waste end of the RO MEMBRANE and restrict the flow with it just like a fixed flow restrictor would only with a ball valve and PSI guage (watching the pressure) I can adjust it perfectly. I never said I restrict the input of the membrane....that would cause your RO to not work at all.
 
:thumbsup:Darryl-
Thanks for clarifying. It really read like you were putting a restriction on the incoming/upstream water - I could not imagine why one would want to do that, so - I did make an effort to clarify to the OP.
My faith in you is restored!

T
 
I re-read my post and it does seem that way. But I only put the PSI guage on the input end (after prefilters and right before the membrane) and the ball valve goes on the waste out of the membrane. When you adjust the ball valve you can watch the pressure on the membrane go up and down.
 
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