This is the discharge end of the line. The shut off is needed to:
A) shut the flow off and the pump
B) maintain pressure on the membranes
I crack the shut off valve about 1/2 open when running the system. If you open it up the water just circulates and will not go through the membrane.
If you build one do not get worried if it does not appear to be working at first it takes a 5 minutes or so to fill everything and push the water through the membrane. You will get discharge sap much sooner than water.
Below is the pump.
Simple in line and out line.
Here is the mess.
It does not matter how you do it but you need to have a larger line that acts as a manifold so all the membranes have equal pressure.
I used a 3/8” Inside diameter line as the manifold and added two tees that tees off from with1/4 lines. I want to make a 2 inch PVC line as the manifold. I will do that after the season hopefully if it is safe to go to Menards or Home Depot again.
It would not function differently, but would be neater with less lines. I would also like to use a manifold on the discharge side so I would have one 1/2 inch line instead of 4, 1/4 inch lines dumping water.
When making one of these remember they might be marked backwards. What the membrane instructions considers waste water is what we need to save.
At the end of the “manifold” I have a line running to a small pressure tank. This buffers your pump so it is not constantly starting and stopping.
Remember at the end of the year you have to flush that with pure water ( actually you need to do the whole system) which is why I collect the “distilled water”.
After flushing with clean water pull out the membranes and allow them to dry, then store them in the freezer so no mold can start inside them. Do not use bleach on the membranes it will destroy them.
After pulling the membranes flush the system with a bleach solution. Then put it away for the year. Rinse the bleach out at the beginning of the next season. You do not want mold ruining your syrup.
Below is the small pressure tank I use. Note the mess of hoses, which is why I want a manifold.
I use a small garden tractor battery to power the pump. I keep the battery hooked up to a trickle charger during the season.
Last but not least is my pressure gauge.
It is reading over 60 psi. Which means I have no leaks!!
Good luck if you decide to built one, they will save you time and money. As I recall I got the membranes and cases for $13 each, the pressure tank at a unclaimed freight or home store and was about $10. I might have $50-$60 in lines and connections.
Which means I have around $200 total in the system, but to buy an RO system will run $600 or more.
This system will serve my needs for years. Last year I just had one membrane to test it and see if I could get it to work. I am not sure what the limit for the number of membranes would be, I am guessing the discharge hose on the pump would decide that. I think the pump has a 1/2 discharge if you wanted to make a larger system.