First I apologize for the long post :).

Based on your post above that your have the mighty mite from airwater ice (50gpd with a minimum rejection rate of 96%)

Tap TDS: 108 (X)

RO TDS: 32 (Y)

(X-Y) = 108-32 = 76

(X-Y) / X = 76/108 = 70.37% rejection rate

So 70.37% is what your membrane is currently rejecting, so in Filmtecs specs it should be replaced since it is below the 96% minimum.

As far as output goes, the "Acceptable" ratio of production to waste is somewhere between 1part production to 5 parts waste (1/5) and (1/3).

I can already tell that something is off with your membrane because my 90GPD unit produces about 2 3/4 cups of waste in 1 minute and since your unit does 40GPD less yet your waste is 5x mine. Your waste should theoretically be less.

Just for the sake of completeness lets figure out what your max production output should be so that we can figure out what your waste output should be.

Expected GPD = Rated GPD * WaterPressureCorrection * TemperatureCorrection

Since your Water Pressure is unknown we will use the average (55psi) and since your Temperature is unknown we will use my average water temperature (61F) :).

TemperatureCorrection(61) = 0.754

WaterPressureCorrection(55) = 55 / 61 = .902

Expected GPD = 50GPD * .902 * .754 = 34GPD is probably pretty close to the most you should get from your unit per day. Since the most waste you should get is 5 times the production 5 * 34 = 170Gallons of waste or 170/1440(minutes in a day) = .118(Gallons per minute)

16 cups of water per gallon .. so .118gallons per minute = 1.888 cups of waste water per minute (MAX at a 5/1 ratio with a 50GPD unit)...

There may be some mistakes in the math above, but based on your waste output alone, I would still think the membrane is bad.

2. 108

3. no idea

4. 32

6. 2/3 cup (and I see floaties)

http://spectrapure.com/RO-RODI/ADD-ONS

I have a couple of questions for you though to see if there is a larger problem at hand.

If you want to see how efficient your membrane is or to see if that could be an issue, please answer the following:

1. What is your water temperature going into your unit?

2. What is the TDS of your tap water?

3. Do you know what your water pressure is?

4. What is the TDS of the water coming straight out of your membrane after it has been running for longer than 15 minutes?

5. What is your RO Unit waste output? (Put the waste line of your RO unit into a measuring unit and time it for 60 seconds and note how much waste there was in that time period)

6. What is your RO Unit production output? (Put the production line of your RO unit directly after the membrane into a measuring unit and time it for 60 seconds and note how much production water there was in that time period - once again this is right after the membrane)

When I first started diagnosing my RO unit I found that my membranes only last about 1.5 years before fouling up so I know I have something in off going on with my source of water, but it also lets me know that I need to replace those which lowers my overall cost of DI resin because I don't burn through it as often.