RO/DI question

[kware]

I'm sure that different brands are different but I'll settle for a ballpark answer. I am wondering what the minimum and maximum working pressures are for most RD/DI systems. I have well water and the pressure varies from 38 to 60 PSI. Do I have enough pressure or will I have to buy a booster pump. Also will they filter out bacteria.
Does anybody have a chart or a Calculator to figure water pressure changes for changing pipe size if there is such a thing? I might be making this harder than it has to be.

[kau_cinta_ku]

60psi is about where you want it. if it runs most of the time at around 40psi then i would suggest a booster pump. even though it will still work at 40 psi you will get more waste as your membrane won't be working to it's fullest.

[AZDesertRat]

40 psi is the minimum. RO membranes are more efficient at higher pressures though so 60 to 90 is optimal. I run mine at 90 to get both the maximum production and the best possible water quality.
The waste will be the same at 40 as it is at 60 or 90, 4:1, if it is set up correctly. The difference is the efficiency.

[kware]

If the waste is the same at 40 as it is at 60 then I have no problem waiting longer for the water. So I don't have to buy a booster pump. But will the water still 99.9 percent pure at 40-60 PSI

[Roland Jacques]

<a href=showthread.php?s=&postid=12126324#post12126324 target=_blank>Originally posted</a> by kware
If the waste is the same at 40 as it is at 60 then I have no problem waiting longer for the water. So I don't have to buy a booster pump. But will the water still 99.9 percent pure at 40-60 PSI
I saw an RODIs at very low pressure just make waste water with no Good water at all. The prefilters were dirty and the pressure was very low.

The waste is not the same at different PSIs. If your restrictor is not adjustable you may have 8:1 ratio at 40PSI and cold water, or 3:1 at 80 PSI... Most RO Resistors are preset and are not adjustable, set for certain PSI (i think 60 is most common) and temp to get 4:1.

You can adjust a ajustable restrictor/resistors to make your RO get 4:1 at 40 PSI.

[kware]

thanks Roland
I think I'll try to get by without a booster pump

[AZDesertRat]

At 40 psi you will not get the water quality you will at 60 or 80 psi. It takes sufficient pressure to pass through the membrane. You can get the adjustable flow restrictor or a capillary tube type and cut it to fit your unique conditions but without the pressure your water quality will suffer a couple of percent or more. The problem there is it eats DI resin must faster since the RO only TDS will be higher. Whatever you do do not try to feed it warm or hot water by trying to blend the water. It can and will melt a membrane in a heartbeat,