RO membranes work more efficiently under high pressure, they have better rejection rate; so to what level can I increase the pressure? (for domestic tfc membrane) This value is stated as 150 psi on Dupont's site, will the membrane be damaged around this amount of pressure, shorten its lifespan? I have a powerful pump, i will save water.
What is the max safe working pressure for RO membranes?
- Thread starter Tobias.d
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POU RO systems are usually rated to around 90 psi.
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I used it for years with 120psi pressure, it worked properly and gave more rejection. Now i have a stronger pump and i wonder about its true limits. There are people who say that up to 300 psi of membrane will not be damaged, i wish i could confirm this from a professional.
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Bannerman
Well-Known Member
There is more to consider than the membrane when planning to increase pressure. I don't know about Germany, but in North America, residential plumbing is designed for a working upper limit of 80 psi, with a minimum tested failure pressure typically 2X the working pressure rating. If your RO is designed similarly, while the system including filter housings, tubing, ASV, drain flow restrictor etc, may tolerate 120 psi, that pressure is likely exceeding each component's rated working pressure. Unless the components are designed for extreme pressure, any further pressure increase may cause a catostraphic failure which could result in extensive damage to your home.
I suspect the 150 psi mentioned on the Dupont site will be applicaple to only specific membranes from the wide variety offered. I also anticipate the pressure rating will be differential pressure across the membrane.
As a typical ASV will shut off RO production when the storage pressure rises to approx 60% of the feed pressure, your current 120 psi incoming pressure will permit the permeate water in storage to rise to ~72 psi. If a Permeate Pump is not utilized, there will be up to 72 psi backpressure placed on the membrane, resulting in ~48 psi pressure differential across the membrane when the storage tank is almost filled.
When the system is equipped with a Permeate pump, that will reduce/eliminate back pressure on the membrane caused by the RO water in storage, thereby increasing the pressure differential across the membrane. This will allow the membrane to function more efficiently to not only reject TDS, but also to increase the production rate thereby requiring less run time and less rinse water discharge to drain each day.
Because backpressure will no longer be an issue, the storage pressure maybe increased. While some remove the ASV and allow the permeate pump to continue filling the storage tank until pressure is equalized, that will unfortunately result in increased TDS in the RO water.
The recommended method for shutoff is to use a higher pressure ASV which will stop production when storage is ~90% of the feed pressure. When only a Permeate pump shuts off production, even a tiny amount of water removed from storage will cause production to restart which will result in higher TDS when small amounts of water are repeatedly produced. A 90% ASV will restart production when the storage pressure has decreased to approx 70% of the feed pressure which will cause a greater quantity of water to be produced each run, which will dilute the TDS that will 'creep' through the membrane each time production commences.
See post #18. https://terrylove.com/forums/index.php?threads/ro-booster-pump-vs-membrane-rate.90912/
I suspect the 150 psi mentioned on the Dupont site will be applicaple to only specific membranes from the wide variety offered. I also anticipate the pressure rating will be differential pressure across the membrane.
As a typical ASV will shut off RO production when the storage pressure rises to approx 60% of the feed pressure, your current 120 psi incoming pressure will permit the permeate water in storage to rise to ~72 psi. If a Permeate Pump is not utilized, there will be up to 72 psi backpressure placed on the membrane, resulting in ~48 psi pressure differential across the membrane when the storage tank is almost filled.
When the system is equipped with a Permeate pump, that will reduce/eliminate back pressure on the membrane caused by the RO water in storage, thereby increasing the pressure differential across the membrane. This will allow the membrane to function more efficiently to not only reject TDS, but also to increase the production rate thereby requiring less run time and less rinse water discharge to drain each day.
Because backpressure will no longer be an issue, the storage pressure maybe increased. While some remove the ASV and allow the permeate pump to continue filling the storage tank until pressure is equalized, that will unfortunately result in increased TDS in the RO water.
The recommended method for shutoff is to use a higher pressure ASV which will stop production when storage is ~90% of the feed pressure. When only a Permeate pump shuts off production, even a tiny amount of water removed from storage will cause production to restart which will result in higher TDS when small amounts of water are repeatedly produced. A 90% ASV will restart production when the storage pressure has decreased to approx 70% of the feed pressure which will cause a greater quantity of water to be produced each run, which will dilute the TDS that will 'creep' through the membrane each time production commences.
See post #18. https://terrylove.com/forums/index.php?threads/ro-booster-pump-vs-membrane-rate.90912/
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Will this pump only supply water to the RO filter?
This must be a whole house unit? I think the max pressure should be no more than 150. I remember seeing the curve somewhere of psi/rejection flattening on a graph. not much is gained past 140-150. ^^Bannerman explains a lot.
ditttohead
Water systems designer, R&D
Each membrane has a specific technical rating. There is a lot more to it than just raising the pressure. Use the mebrane manufacturers design parameters. Here is a chart from our catalog. We tweak these based primarily on temperature. If you have lower water temperature (<77F) then we can put a lower pressure membrane in to compensate for this reduction. This is more of a classroom session question that would require about an hour of time to get even through the basics.
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