A little investment could save you money and time.

I started producing maple syrup as a hobby over 20 years ago. I began with 10 buckets and now have 100 taps on a sap line all funneling to my woodshed that transforms into my sugar house for a couple of months each year in the spring. The timing is perfect. The firewood is down to the last couple of rows, leaving room for my 2×4 evaporator.

I wanted to take a few minutes to share my experience regarding the economics of the homemade reverse osmosis (RO) unit that I built. Hopefully, this will help you in your decision to build one!

How It Works

I took this video toward the end of the 2017 sugaring season. This is the RO unit that I built last year using Hodorskib’s design. Another membrane was added to the system this year for a total of 5 vs. the 4 in this video. Having 5 has allowed me to go from an average of 2-3% sugar content to close to 10%. The difference is that with 2.15%, it takes 40 gallons of sap to make a gallon of syrup. With 10%, it takes 8.6 gallons of sap to make 1 gallon of syrup. Being just under 10% sugar on average, I’ve reduced the ratio from about 40:1 down to just less than 9:1.

The system certainly isn’t large, but it’s perfect for up to 120 taps. It runs off of a small pump that barely uses any electricity. It processes about 6-7 gallons of sap per hour. Essentially, it removes a bunch of water from the sap before the sap ever gets boiled. Plus, it can run overnight if desired. If the sap tank gets empty, the pump that is used is safe to run dry without doing any damage.

Less means more

Here’s the math…which creates huge savings in time and fuel consumption-

With my propane, 2’x4′ evaporator (which isn’t very efficient), I boil off about 7+ gallons of sap per hour.

In a perfect season with our 83 taps and no vacuum, the potential is there for 830 gallons of sap. (I added a vacuum system this year- but I’ll stick to these numbers for this example.)

Direct out of the trees without running through the reverse osmosis system, if the sugar content of the sap was 2.15%, it would take 40 gallons of sap to make 1 gallon of syrup (40:1). That means that 39 gallons need to be boiled off per gallon of syrup. 39 gallons divided by 7 gallons per hour, is just over 5.5 hours of boiling time per gallon of syrup.

If after running those same 40 gallons through reverse osmosis the sugar content was at 10%, it would take 8.6 gallons of sap to make 1 gallon of syrup (8.6:1). That means that 7.6 gallons need to be boiled off per gallon of syrup. 7.6 gallons divided by 7 gallons per hour, is just over 1 hour of boiling time per gallon of syrup for me.

Automation and ease

Note that the RO unit just needs to be fed sap to run. There’s a little prep and a little cleaning after, but both of those consist of allowing water to run through the system and occasionally running RO soap to clean the membranes if the pressure starts to not hold up. All of these only require a few minutes of actual work and letting the RO do its thing. As I said, it processes about 6-7 gallons of sap per hour.

As stated, my evaporator isn’t very efficient, but it works for me and allows for convenience…I can turn it on and turn it off. I also work from home and have a wifi cam that I monitor which looks down on it while it’s doing the work for me and go out every hour at least to make sure there’s plenty of sap in the overhead tank. I know this all sounds high-tech, but we live off-grid, 5 miles up a dirt road, so…it’s sort of a wash.

Now, the real savings and how it pays for itself…

I have a 120-gallon propane tank that gets filled to 80%, or 96 gallons. My evaporator uses 1.5 gallons of propane per hour.

Going back to the 40:1 ratio, at 5.5 hours of boiling, evaporating 7 gallons of sap per hour to get 1 gallon of syrup, I would use 8.5 gallons of propane. If propane costs $2.25 (USD) per gallon, that’s $12.38 (USD) to make one gallon.

At the 8.6:1 ratio, I need to boil for just over an hour to get 1 gallon of syrup. At $2.25 (USD) per gallon of fuel, that’s about $2.50 (USD) per gallon of syrup.

With no RO, 830 gallons of 2.15% sap would make 20.75 gallons of syrup. It would require boiling off 808.25 gallons of sap. At 7 hours per gallon, that would take 115 1/2 hours (I rounded up).

115.5 boiling hours x $2.25(USD) per gallon of propane = $259.88 (USD)

With reverse osmosis, those same 830 gallons would be reduced down to 199.25 gallons (rounded up again) of 10% sap. This would require boiling off 178.5 gallons of sap. At 7 hours per gallon, that would take 25.5 hours.

25.5 boiling hours x $2.25 (USD) per gallon of propane = $57.38 (USD)

A fuel savings of $202.50 (USD) and a time savings of 90 hours

The RO system at the time of this writing costs around $350 – $400 (USD) including the membranes, depending on a few items that you can choose to add or do without. The membranes that I use cost around $35 (USD) each. However, these can be re-used at least a couple of years in a row with proper care, possibly 3 years before having to be replaced.

I know that this same system is being tested with fewer membranes that will allow more sap flow per day, Hodorskib said that he will post that data at the end of the 2018 season.

Is it worth it?

I’ve broken this down pretty deeply, but honestly, the amount of time that I’ve saved in addition to how quickly it pays for itself is incredible. Anyone interested could replace the numbers that I’ve used with their own to see how it might work for them.

Note one important thing- The sugar content of my sap is almost always 2-3%. I’ve read where others have as low as 1.25%. This would be a factor, but I think even more reason to use an RO system like this. I also know that not everyone gets 10% sap concentrate from this RO and that 6-7% is often mentioned. I don’t know why mine consistently gets that “good” of a percentage. Then again, I don’t know why the sap won’t run on a perfect day and will run for three days straight on what I consider three not-so-perfect days.

Are you a sugar maker? Have you considered adding a homemade reverse osmosis system to your process?

Many thanks to Hodorskib and everyone in the sugaring community for being so helpful with all aspects of sugaring!