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I have only managed to get to 12% by recirculating however, two things happened:
1. The system slowed way down
2. The membranes clogged to the point it took a very long time to clean and recover
3. I have also heard from others that the membranes will start passing sugar as well - I have never experienced that though
I try not to go above 8.5-9% it is not worth the hassle of the extended cleaning.
If you are worried about freezing, just recirculate. I ran mine in an unheated garage overnight with temps down to 20. I recirculated but setup a shoplight on the ro just on case. After running it this way overnight, I noticed that the residual ice on my feed tank was gone. I am assuming that the pump probably warms the sap a little as it runs through. The shoplights may have helped a bit too. I just would not let sit in freezing temps when not circulating.
Hodor thanks for all the detailed information. I read your site and logs for production. I'm really amazed at how much you are making with the ro and small evaporator. I'm thinking of going a bit bigger next year. Do you think a 2x4 continuous flow pan would match this setup?
Thanks
As I have said previously this year I have been very diligent about keeping the membranes as clean as possible. If your sap is usually 2% you should be able to process 150-175 gallons a day to 7.5-8% but that would be the maximum with this little RO. It is really designed for around 100 taps if you plan on processing and boiling daily. If not I would look at some of the other threads and build something a little bigger.
ok then,,,virgin no more...I went from approx 2% to approx 4% over 25 gallons at 37 deg sap. My psi was about 125 PSI. what could be done to increase that 4%?
[edit] I closed the valve a little and psi = 140 and 6% sap.
Is there a max psi?
How many and what size membranes do you have? That will influence amount of water removed.
per the authors instructions I have 4 150 gpd membranes
With the 4 membranes 6% and 140psi is a good number. Remember you just removed 2/3rds of the water and now are at 14:1. Congratulations!
Hodorskib-
How often do you flush the RO system? I have the same homemade system (1st year using it) and I found that I can run sap at ~100psi and get 6-7%. I have been flushing the system clean every drum that I run through (~60 gallons) and the performance seems to be consistent. I change the 5 micron filter for every drum. Do you do something different?
Thanks
The cleaner you keep the membranes the better the performance. I have been using an RO soap this year and doing a wash after each run and after 4 weeks and over 2,000 gallons of sap the system is running as well as the first day. I posted this information to my website.