inexpensive RO/DI units on eBay... thoughts?
- Thread starter SpiderWhistle
- Start date
This is somewhat of a long story. To simplify it a little, let's talk about an RO system, rather than an RODI for now.
Membranes function in part based upon the DIFFERENCE in pressure on the high pressure side of the membrane vs the pressure on the low pressure side of the membrane. Let's say your line (plumbing) pressure is 60 psi, and you send your RO water to an open reservoir. As far as the membrane "knows," it has 60 psi on one side of the membrane and 0 psi on the other, for a difference of 60 psi.
No connect that RO output line to a pressurized storage container instead of an open reservoir. In a typical system equipped with a hydraulic shut off valve, the system will continue to push water into the pressure tank until the tank pushes back against the membrane with (in this case) 40 psi (66% of line pressure). So as the tank gets more and more full, back pressure on the membrane increases and the DIFFERENCE between the high and low pressure sides of the membranes continues to decrease - until you have 60 psi - 40 psi = 20 psi net driving pressure. You can imagine how poorly the membrane will perform in terms of rejection and flux (amount of water purified) as the pressure tank gets more and more full.
This is why water delivered to a DI stage should always come directly from the membrane, and should be delivered to an open, or "atmospheric" tank.
Russ
Membranes function in part based upon the DIFFERENCE in pressure on the high pressure side of the membrane vs the pressure on the low pressure side of the membrane. Let's say your line (plumbing) pressure is 60 psi, and you send your RO water to an open reservoir. As far as the membrane "knows," it has 60 psi on one side of the membrane and 0 psi on the other, for a difference of 60 psi.
No connect that RO output line to a pressurized storage container instead of an open reservoir. In a typical system equipped with a hydraulic shut off valve, the system will continue to push water into the pressure tank until the tank pushes back against the membrane with (in this case) 40 psi (66% of line pressure). So as the tank gets more and more full, back pressure on the membrane increases and the DIFFERENCE between the high and low pressure sides of the membranes continues to decrease - until you have 60 psi - 40 psi = 20 psi net driving pressure. You can imagine how poorly the membrane will perform in terms of rejection and flux (amount of water purified) as the pressure tank gets more and more full.
This is why water delivered to a DI stage should always come directly from the membrane, and should be delivered to an open, or "atmospheric" tank.
Russ
inexpensive RO/DI units on eBay... thoughts?
So would this decrease the life of the membrane? Like I said before I've measured the TDS of straight to the DI stage and out versus from the storage container, through the DI stage and out and it always reads zero. I understand your explanation, and it makes sense, just curious.
So would this decrease the life of the membrane? Like I said before I've measured the TDS of straight to the DI stage and out versus from the storage container, through the DI stage and out and it always reads zero. I understand your explanation, and it makes sense, just curious.
Guys you haven't heard the name of the product that is fine but only after using it you get to know about the product and it's reliability,just think that you never invested any kinda money on the product so there is no chance of loss,If you like it then keep it other wise it your choice what to do.