I have a typical 4-stage, under-sink RO system with 3 storage tanks. The water flow is excellent and since this issue started, there has been no change in the flow nor the amount of water produced.

Instead of running the discharge line into the sink drain plumbing, I punched a hole in the wall and ran it out to a bucket which is collected and used to water plants.
A couple of months ago, my wife mentioned that said bucket had been empty the last few times she passed by it. I checked to see if maybe the bucket had developed a crack and the water was draining out as fast as it was going in. That wasn't the case.
To verify there was no water being discharged, I opened the RO faucet and let it run for a few minutes to force the system to begin replenishing. I also verified the discharge line was not plugged.
When I closed the faucet, the system began to produce filtered water and refilling the tanks.
Sure enough, nothing was coming out of the discharge line. I then replaced the capillary tube in case it had become plugged, but still no discharge.

I live in AZ which has notoriously hard water. Additionally, the city chlorinates the crap out of the water. A typical sample of my tap water contains the following:
Cl 1.5 ppm
pH 7.4
TDS 500-900 ppm depending on which source the city is currently drawing from .

A sample of the water produced by my RO system today contained:
Cl 0ppm
pH 7.0
TDS 24ppm

The system is still doing its job and is filtering correctly, it's just not creating any waste water. How can this be? I am completely stumped. I thought that if it wasn't creating waste water, it meant the water was just going straight through the system and filling the tanks with untreated tap water. Obviously that isn't the case based on the test results.

Can someone please enlighten me as to what's going on here?

Thank you
Steve
Chandler, AZ

EDIT:
A couple of things I should have noted in my post...
Prior to this issue, the system produced approx 3:1 waste water to treated water.
I replaced the filters and membrane approx 2 mos. prior to this issue arising and there was no change in the output of neither the treated water nor the waste water.
I did an exhaustive search for anything related to this issue to no avail.