RO system pressure

[Tylersizemore5]

Hey guys what’s the best pressure to keep your RO system operating at?

 

[Greg Pack]

depends on the membrane but most run at 175-200 psi. There are low energy membranes that work at around 100 psi

 

[Buckeye Hydro]

We stock membranes spec'ed at 80 psi, 100 psi, 150 psi, and 225 psi.

Realize that these are the test pressures used by the manufacturer. These pressures, along with 77F feedwater (and some other factors) are what allow the manufacturer to claim the output gpd of the membrane. In other words, the manufacturer is saying: If you provide this membrane with X psi pressure, 77F feedwater, (and some other lesser requirements), you can expect X gpd production (typically plus of minus about 15%). Nothing says the factory spec pressures are "ideal." If you run a membrane at pressures above the factory spec, you can expect faster permeate ("RO water") production, and slightly better rejection (i.e., RO water that is slightly more pure).

So check the specs of the specific membrane(s) you have installed - that will give you a starting point. If you don't have any records of which membranes (brand and model) are installed, you can always pull one out and look at the sticker/label on the body of the membrane.

Most commercial RO systems allow you to adjust the pump output pressure. To do this your system should be equipped with a pressure gauge that shows the pump output pressure. You'll see that if you have a needle valve to adjust the concentrate ("brine" or "waste water") flow, as you reduce concentrate flow the pumped pressure will increase. However it is generally not a good approach to adjust concentrate flow to try to hit a target pressure. Rather, use that needle valve to hit a target concentrate flow, and let the pressure fall where it may. Remember that based on membrane diameter you'll have a minimum recommended concentrate flow (typically 1 gpm for 2.5" diameter membranes, and 3 gpm for 4" diameter membranes). If you have proper pretreatment of the RO system feedwater, you'll typically be safe shooting for that minimum concentrate flow. A lot here depends upon how your RO system is plumbed - so check the manual for your specific system. You'll also have either a globe valve on the output of the pump, or an adjustment screw on the side of smaller pumps - both can be adjusted to change the pump output pressure.

Russ

 

[Wash Dragon]

As far as I know, HANNA's RO systems often operate at around 100 PSI.