DIY thoughts

[green4310]

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.

[user587]

Thanks for posting the info. I'm looking waaay ahead and if I can commandeer another nice woods or 2 in future years, I may like to build an RO unit. I'm reading/learning what I can - and appreciate the sharing of info!

[green4310]

Some of this is from another post that I include here to save you looking for it..

First, never reverse flow to wash, run as normal with as much flow as you can. Leave concentrate valve wide open. You do not want to make permeate,only flush/wash the concentrate out. I run premeate first, enough to flush, maybe 50 gal. Then I set up my turkey cooker with around 7 gal permeate and stick all lines into it. I get everything circulating and then light the gas to heat the water. I then trickle in RO soap until I get the PH to around 10 No more than 11. I circulate until the temperature is 110 and no more than 113F. Turn off the gas and continue to circulate until the temp drops to 100-105F. I then connect back to permeate and let flush.
note...If you wash at temp of 77F(25C) max you can go to 12 on the ph.
After a couple of washes, you will get a feel for your own wash times,rinses ect. This is only a guide. I normally let mine circulate soap while I finish up boiling. I start the evap around (1/2-1) hour after the RO. Hope this makes some sense.

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[green4310]

For those of you who, like me use well water for the beginning of the season flush out, or have high mineral sap.
This is where you need to do the acid wash. I do it each year at the end of the season. The acid I use is from the Dow chart and is phosphoric acid. Since this is also used as tank cleaner, it is a twofer. I buy it local for around $30gal for 85%.
The process is the same as for soap wash only this time take the ph the other way down to 3@ 112F or you can go to ph2 if running @77F(25C).

note: higher temps.= weaker solution by 1 number on the ph.

Following the acid wash flush with permeate and then do the soap wash followed by another permeate wash
This should leave your membranes sqeeky clean. For storage get some Leader preservative and use as directed.
I leave my membranes in the machine with presrevative over the year. So far so good.
Some like to remove to store, thats ok too.

Final comment: You should set your RO up so that each tube can be cleaned individually for best results.

[Kev]

well since I have just now begun to think about an R/O system. Ok it was really the other morning when I had been cooking and collecting since 2 pm and it was approaching 5 am the next day. I will show my complete ignorance on this subject.
1) I assume that the pure water output from an RO system is the waste discharge for our perposes and the intended waste or brackish water discharge is our "good stuff"
2)given 1 is true:
can I just buy a couple of 200 gpd residential systems and pump though in parallel for 400 gpd. or do you really just want the actual membrane and not the prefilters in the system (IE do those not discharge their waste?
thanks in advance for any input