I recently had my membranes replaced due to a permeate water gpm drop and was not capable withstanding the ouput being used. Before membranes were changed I was getting 4 to 8 ppm (even when permeate water dropped due to possible fouling). Now after the new membranes, I achieved the maximum product gpm @ a lower pump pressure, but now my permeate ppm has increase to around 17 to 20. My feed ppm on average is around 300, so my current rejection rate is around 93%. My membranes are thin film composite and rated for 98 to 99% rejection. Will the ppm drop over time?
RO Membrane replacement/rejection %
- Thread starter RAAOO7
- Start date
Jeff_L
Well-known member
I'm surprised you changed the membrane out when you were getting 4-8ppm. That's really good. I recently read that you can consider 50ppm or less spot free. After changing membranes at my location, I usually see it run 10-18ppm.
Are you noticing spotting now at 17-20?
Are you noticing spotting now at 17-20?
Greg Pack
Wash Weenie
I don't think it will. Reject% will depend on the membranes. Different ones have different specs. Some of the lower pressure ones allow more junk through.
I assume you changed them because the reject % had gotten too high and your don't use your reject water? If you changed them because of ppm, you shouldn't have. 50 or below is technically considered spot fee, I aim for 25 ppm or below. 4-8ppm is excellent quality water.
I assume you changed them because the reject % had gotten too high and your don't use your reject water? If you changed them because of ppm, you shouldn't have. 50 or below is technically considered spot fee, I aim for 25 ppm or below. 4-8ppm is excellent quality water.
My RO unit makes 2.5 gpm or 3600 max. The reason why I changed my membranes not because of the ppm. The flow rate dropped to around 1.25 gpm, during busy times, the unit could not keep up with the output being used. Also the motor was running almost double the time to make the same amount of water.
There is no noticeable spotting, I guess I'm spoiled when I use to 4 to 8 ppm.
"50 or below is technically considered spot fee, I aim for 25 ppm or below."
I am having an issue with small specs being on the vehicle's windshield when the vehicle gets done going through my off board dryers. My spot free water has tested from 40-45 ppm range. The speaks are tough to get off the windshield and Im wondering if my customers are noticing (no complaints but I can see them on mine). I had an electronic water softener for a year before getting my current softner. Do you think these specks are being caused by my spot free water? I thought the wind was possibly blowing soap in the dryer motor and then blowing it on the car. I have an open short bay with the dryers close to the end of my machine, but after some testing on a piece of plexy glass I don't think that is the case..
smallwash
I am having an issue with small specs being on the vehicle's windshield when the vehicle gets done going through my off board dryers. My spot free water has tested from 40-45 ppm range. The speaks are tough to get off the windshield and Im wondering if my customers are noticing (no complaints but I can see them on mine). I had an electronic water softener for a year before getting my current softner. Do you think these specks are being caused by my spot free water? I thought the wind was possibly blowing soap in the dryer motor and then blowing it on the car. I have an open short bay with the dryers close to the end of my machine, but after some testing on a piece of plexy glass I don't think that is the case..
smallwash
Greg Pack
Wash Weenie
Water is bordeline spot free at 40-45ppm. If it mixes with tap rinse water, the result can be water that is above the threshhold of spot free. Dripping water off the gantry or soap being blown out of the cracks and crevices can also cause issues.
