morty
09-23-2007, 05:14 PM
(This is a sort of long post but there was no way to explain this briefly)
I normally run a permeate pump on my RO/DI system because it supposedly is helpful when using a pressurized canister for storing RO. I take RO from the filter before it runs thru the DI stage, and run it to a 3 gal pressurized storage tank in my kitchen, which feeds my fridge water dispenser. The permeate pump is supposed to help prolong membrane life, save water, and increase the storage pressure, which it seems to do.
I recently needed to make a large amount of RO/DI, so I thought I'd temporarily remove the permeate pump because I thought it would put unneccesary wear on it (supposedly the permeate pump is only beneficial when filling a pressurized system. If the RO/DI outlet is going to an open container, it's not needed.) I began to fill the containers, and planned on putting the pump back in when I was got enough RO/DI.
After a couple hundred gallons of RO/DI was produced, I noticed my DI resin's color had changed, an its output was no longer at 0 ppm TDS, but was somewhere between 1 and 2. So I decided to stop making RO/DI until I got new DI resin, and I reconnected the permeate pump because my fridge water pressure had gotten low. I also needed some more RO/DI in a different container, and I thought I could live with some of it being higher in TDS, so I started making more RO/DI even though the resin was supposedly exhausted and I hadn't gotten new stuff yet, except this time the permeate pump was in place.
(When permeate pumps are running, they make a clicking noise every few seconds, and the water comes out in pulses at the same rate as the clicking. What happens when this pulsed water is run into DI filters is that the resin bed lifts and falls slightly with each pulse.) So today I checked the DI filter's outlet, and it's back at 0 ppm! Also, the resin seems to have changed back to the non-exhusted color!
So I'm wondering if the slight mixing of the resin that occurs when the permeate pump is running somehow increases the life of the resin. Maybe some channeling of water occurs in the resin when it is sitting stationary (without the permeate pump) and with RO water being steadily pumped thru it. The mixing that happens with the pump may keep this channeling from happening. And when it got re-mixed, some of the unexhaused resin granules were able to take up solutes from saturated granules, and it sort of rejuvenated the bed? I might be all wet here, but I thought I'd share what I observed.
I normally run a permeate pump on my RO/DI system because it supposedly is helpful when using a pressurized canister for storing RO. I take RO from the filter before it runs thru the DI stage, and run it to a 3 gal pressurized storage tank in my kitchen, which feeds my fridge water dispenser. The permeate pump is supposed to help prolong membrane life, save water, and increase the storage pressure, which it seems to do.
I recently needed to make a large amount of RO/DI, so I thought I'd temporarily remove the permeate pump because I thought it would put unneccesary wear on it (supposedly the permeate pump is only beneficial when filling a pressurized system. If the RO/DI outlet is going to an open container, it's not needed.) I began to fill the containers, and planned on putting the pump back in when I was got enough RO/DI.
After a couple hundred gallons of RO/DI was produced, I noticed my DI resin's color had changed, an its output was no longer at 0 ppm TDS, but was somewhere between 1 and 2. So I decided to stop making RO/DI until I got new DI resin, and I reconnected the permeate pump because my fridge water pressure had gotten low. I also needed some more RO/DI in a different container, and I thought I could live with some of it being higher in TDS, so I started making more RO/DI even though the resin was supposedly exhausted and I hadn't gotten new stuff yet, except this time the permeate pump was in place.
(When permeate pumps are running, they make a clicking noise every few seconds, and the water comes out in pulses at the same rate as the clicking. What happens when this pulsed water is run into DI filters is that the resin bed lifts and falls slightly with each pulse.) So today I checked the DI filter's outlet, and it's back at 0 ppm! Also, the resin seems to have changed back to the non-exhusted color!
So I'm wondering if the slight mixing of the resin that occurs when the permeate pump is running somehow increases the life of the resin. Maybe some channeling of water occurs in the resin when it is sitting stationary (without the permeate pump) and with RO water being steadily pumped thru it. The mixing that happens with the pump may keep this channeling from happening. And when it got re-mixed, some of the unexhaused resin granules were able to take up solutes from saturated granules, and it sort of rejuvenated the bed? I might be all wet here, but I thought I'd share what I observed.