How many trees is too many?

Thank you for patience with my RO questions. I have a few more.

If I have 50 gallons of raw sap and set the needle valve so that half of the flow goes into the concentrate barrel and the other half goes into the permeate barrel, I would have 25 gallons of each in each barrel. Let’s say that took 6 hours to accomplish. Now if instead of putting the concentrate into a separate barrel, I returned it back to the original sap barrel and ran it for 12 hours, would at one point the flow on the permeate side automatically lessen because there is less water to remove?

I understand that if you have reduced the sap from 50 gallons to 25 gallons, you have 50% less fluid to boil off saving 50% of the time and fuel. Would there also be additional savings because not only there is half the volume to boil, but it is concentrated, so it should take less time to boil 25 gallons of concentrated sap versus raw sap?

If I have lots of sap and my evaporator can boil at a rate of 8 gph and I boil for 8 hours, that is 64 gallons that I can boil. To get 64 gallons of concentrated sap, I would have to run 128 gallons of raw sap through the RO. For me that means stopping the unit twice to refill the 50 gallon raw sap barrel. Would it be okay to clean the membrane at the end of the three runs?

Attachment 22588Attachment 22588

I am just a small operator with mostly homemade equipment, but I will try to answer as best I can. Others with more experience please feel free to correct me. I have tried to include a photo of my RO for reference.

On your first question if I am understanding it correctly: if you run the concentrate hose back into the main holding tank and run the permeate hose to a separate tank AND you keep the pressure in the system constant, you will notice the permeate flow rate slowly decrease over time as the sugar content in the main tank rises. However, the permeate flow rate will drop off slowly.

Second question: I’m not sure of the physics on that one. The higher sugar content in the concentrated sap will raise the boiling point, but it’s been my experience that water seems to leave my evaporator at a pretty constant rate until right near the end when it gets really touchy.

Third question: I think that would be ok. I’ve run 250 gallons through mine in one go before giving it a thorough cleaning. I suppose too it probably depends on the sugar content and clarity of the sap. The sap from my trees is typically pretty low in sugar content. If it’s 2% it’s a great run. 1.5% is more normal.

Quote:

---

Originally Posted by 82cabby

Attachment 22588Attachment 22588

I am just a small operator with mostly homemade equipment, but I will try to answer as best I can. Others with more experience please feel free to correct me. I have tried to include a photo of my RO for reference.

On your first question if I am understanding it correctly: if you run the concentrate hose back into the main holding tank and run the permeate hose to a separate tank AND you keep the pressure in the system constant, you will notice the permeate flow rate slowly decrease over time as the sugar content in the main tank rises. However, the permeate flow rate will drop off slowly.

Second question: I’m not sure of the physics on that one. The higher sugar content in the concentrated sap will raise the boiling point, but it’s been my experience that water seems to leave my evaporator at a pretty constant rate until right near the end when it gets really touchy.

Third question: I think that would be ok. I’ve run 250 gallons through mine in one go before giving it a thorough cleaning. I suppose too it probably depends on the sugar content and clarity of the sap. The sap from my trees is typically pretty low in sugar content. If it’s 2% it’s a great run. 1.5% is more normal.

---

Thank you!

What size (gpd) membranes do you have and is the light bulb for a heat source?

What do you use to measure the sugar content of your sap? A refractometer, or a hydrometer?

Quote:

---

Originally Posted by 82cabby

Attachment 22588Attachment 22588

I am just a small operator with mostly homemade equipment, but I will try to answer as best I can. Others with more experience please feel free to correct me. I have tried to include a photo of my RO for reference.

On your first question if I am understanding it correctly: if you run the concentrate hose back into the main holding tank and run the permeate hose to a separate tank AND you keep the pressure in the system constant, you will notice the permeate flow rate slowly decrease over time as the sugar content in the main tank rises. However, the permeate flow rate will drop off slowly.

Second question: I’m not sure of the physics on that one. The higher sugar content in the concentrated sap will raise the boiling point, but it’s been my experience that water seems to leave my evaporator at a pretty constant rate until right near the end when it gets really touchy.

Third question: I think that would be ok. I’ve run 250 gallons through mine in one go before giving it a thorough cleaning. I suppose too it probably depends on the sugar content and clarity of the sap. The sap from my trees is typically pretty low in sugar content. If it’s 2% it’s a great run. 1.5% is more normal.

---

When you have multiple ro membranes/housings, does the permeate line from each filter separately go into the permeate drum?

Edit: found a drawing on line to answer my question.

Attachment 22589

Yep, the lightbulb is connected to an old thermostat. I set it to about 38 to keep the unit from freezing. The method shown several posts ago is much more modern and safer. I am going to try to convert mine.

Membranes are 150 gpd.

I use a hydrometer for measuring sugar content.

And mine is plumbed just like the diagram. The permeate from each membrane is routed out via a common line and the concentrate from one membrane feeds into the next one in line. I rotate the membranes several times a season.

It’s not a fancy setup but man does it save boiling time. I go from 1.5% to 6% in one pass through. I could probably get higher with some tweaking. My fuel consumption per gallon of finished syrup is way down from where it was before I had the RO.

Quote:

---

Originally Posted by 82cabby

Would you mind posting links to the parts you used for the heater, including the 24v power supply and controller? That is a much better system than the light bulbs I use!

---

Inkbird ITC-1000F 2 Stage Temperature Controller* https://www.amazon.com/dp/B07R46D44T...ing=UTF8&psc=1

WeiMeet 2 Pack Aluminum Heat Sink
https://www.amazon.com/dp/B08BZLC873...ing=UTF8&psc=1

Watlow 100w silicone strip heater (110vac)

Quote:

---

Originally Posted by Swingpure

Thank you for patience with my RO questions. I have a few more.

If I have 50 gallons of raw sap and set the needle valve so that half of the flow goes into the concentrate barrel and the other half goes into the permeate barrel, I would have 25 gallons of each in each barrel. Let’s say that took 6 hours to accomplish. Now if instead of putting the concentrate into a separate barrel, I returned it back to the original sap barrel and ran it for 12 hours, would at one point the flow on the permeate side automatically lessen because there is less water to remove?

I understand that if you have reduced the sap from 50 gallons to 25 gallons, you have 50% less fluid to boil off saving 50% of the time and fuel. Would there also be additional savings because not only there is half the volume to boil, but it is concentrated, so it should take less time to boil 25 gallons of concentrated sap versus raw sap?

If I have lots of sap and my evaporator can boil at a rate of 8 gph and I boil for 8 hours, that is 64 gallons that I can boil. To get 64 gallons of concentrated sap, I would have to run 128 gallons of raw sap through the RO. For me that means stopping the unit twice to refill the 50 gallon raw sap barrel. Would it be okay to clean the membrane at the end of the three runs?

---

In theory the boiling point increases and evaporation rate slightly decreases as sugar concentration increases. Not anything you will notice as others have said.

You don't need to wait to get that much concentrate to start. You just need enough for a boil. If you have your steam pans 2 inches deep, that's less than 10 gallons total of volume in your 5 pan setup. If you get 10 gph evap, you have warm up and cool down time and enough sap concentrate for a 2 or 3 hrs boil. This gives you time for filtering, bottling cleanup etc.

You will figure out your rhythm for gathering, ROing, boiling etc but for me the weather influences it. Overnight freezes make it tough to run an outdoor RO overnight, or to do it the next day. I RO, boil, filter and bottle it all everyday so I don't fall behind.

As to your question about speed... there are posts that detail this out. Your speed of concentration depends upon a multitude of factors like temperature, pump flow rate & pressure, membrane sizes, configuration, and number of membranes. Keep in mind the gdp rating of membranes is for the permeate output but in practice you will see far less than this due to temperature effects. I have seen an average of 5 gallons of water removal per hour for each 400 gpd membrane in a series setup. 400gpd membranes are faster at creating permeate and not much more $ than the smaller ones nowadays.

Also, you have to have enough flowrate across membrane surfaces in your waste/concentrate output to prevent fouling of the membranes. Its best to keep recovery rates around 15% (permeate out flowrate per membrane / input flow rate per membrane x 100).

Lastly.... on 3/16 on sugar maples ...I would suggest you plan for over 1 gallon per tap for every day the weather cooperates. You will inevitably have a couple days per year where you get double that.

If you build an RO like these, its easy to expand and add another membrane the following year. Just get the bigger pump (same price really) so you have enough flow rate to support more membranes in series.

I have the same setup as 82cabby, but I have 5 membranes. I run the system typically 100 - 120 psi and process about 10 gallons of sap/ hour. It's slow, but I generally run it while I'm sleeping. I have found it runs a little faster if it's warmer. Based on 10 gal/hour and how many gallons of sap I have to run, I set up the power on the pump to a timer and let it run and stop automatically. I typically run it through twice and have had good success with 3% sap getting to 11 - 13%. I did find the quality of the membranes to matter, the dow filmtec ones were higher % than whatever cheap ones I got last year.

On timing - I boil once/week and try to run the RO once/week unless I have a lot of sap to run. Generally I try to run the RO the night before I'm planning to boil. Typically Friday night for Saturday boil. I think the biggest amount of sap I had to process was 250 gallons or so. Towards the end of the season the filter clogs up a lot more often and I have to change it frequently to keep the pressure up. The concentrate (especially at the end of the season) absolutely spoils faster than sap. I keep it in the garage so above freezing but not warm, then run it the night before so it has minimal time to go bad.

None of my ideas are new, this website has been amazing for keeping production up despite not having a properly sized evaporator for the amount of trees I tapped: https://sites.google.com/view/mattat...sis?authuser=0

Cost me about $500, best thing I could have done with that money. the RO is a huge time saver.

Quote:

---

Originally Posted by DRoseum

Inkbird ITC-1000F 2 Stage Temperature Controller* https://www.amazon.com/dp/B07R46D44T...ing=UTF8&psc=1

WeiMeet 2 Pack Aluminum Heat Sink
https://www.amazon.com/dp/B08BZLC873...ing=UTF8&psc=1

Watlow 100w silicone strip heater (110vac)

---

Thank you!

I found an inexpensive 150 GPD membrane and housing on Amazon. Is this a case of you get what you pay for and run away from it, or will this do for a couple of years?


Canadian Amazon site:
https://www.amazon.ca/Huining-Water-...s%2C166&sr=8-1

US Amazon site:
https://www.amazon.com/100GPD-1812-C...%2C149&sr=8-19