green4310
02-25-2011, 10:30 AM
The following is some info I picked up from Dow membrane data and my own experiences building and rebuilding my RO over the last four years. When I started the only info I had was the info from the DOW sight. I read through the techno mumbo jumbo and tried to make sense out of it as pertained to DIY. I could see right off that these are not high tech devices and that a lot of smoke and mirrors is put out by the manufacturers of these things to justify their rediculously high prices. Anyway the following are some things to consider in rolling your own. I will say this tho that with all my experimenting I still less than 1/4 the cost of a new one. My unit is, from a practical stand point good for around 1000 gpd(8hrs) this includes cleanup. More than that I would go with the factory guys.
If you DIY you know what you got, you need not call in the high priced repair guy because it is you.
The max flow through a four incher is 16gpm. They recommend at least 10gpm for clean up.
This would include,I assume any leakage coming out the permeate side, which they discourage. In use, the max permeate allowable is 1.6gpm with a minumum of 2.0gpm on concentrate side. You then run up against the max recovery limit of 30%. So...putting it all together for us DIYrs. The most water you can remove on a single pass is 30%. Lets say you have a 5gpm pump and take out 1.5gpm ie 30%, this would leave 3.5gpm of concentrate and keep the membrane happy. The factory guys use feed back to get the concentrate lower and I expect have no problem limiting out the membrane. Us DIYrs have 2 choices, either run the concentrated sap through a couple more times or add membranes. I chose the latter. I use four nf270, and can get 5gpm input down to 1 gpm of 40 degree sap, with 1gpm feed back. Specificaly @ 200psi input, 4gpm permeate, and 1gpm of sweet. The concentrate going through the membrane is 2gpm, but 1gpm is fed back to the pressure pump input. Normally I will run 6gpm in and 2gpm concentrate for 67% and no feed back.
If you DIY you know what you got, you need not call in the high priced repair guy because it is you.
The max flow through a four incher is 16gpm. They recommend at least 10gpm for clean up.
This would include,I assume any leakage coming out the permeate side, which they discourage. In use, the max permeate allowable is 1.6gpm with a minumum of 2.0gpm on concentrate side. You then run up against the max recovery limit of 30%. So...putting it all together for us DIYrs. The most water you can remove on a single pass is 30%. Lets say you have a 5gpm pump and take out 1.5gpm ie 30%, this would leave 3.5gpm of concentrate and keep the membrane happy. The factory guys use feed back to get the concentrate lower and I expect have no problem limiting out the membrane. Us DIYrs have 2 choices, either run the concentrated sap through a couple more times or add membranes. I chose the latter. I use four nf270, and can get 5gpm input down to 1 gpm of 40 degree sap, with 1gpm feed back. Specificaly @ 200psi input, 4gpm permeate, and 1gpm of sweet. The concentrate going through the membrane is 2gpm, but 1gpm is fed back to the pressure pump input. Normally I will run 6gpm in and 2gpm concentrate for 67% and no feed back.