Here is a list for all the parts needed to build a 4 membrane RO system using 150gpd membranes and an Aquatech 8800 pump. I run my system with 6 membranes but have found that there is very little difference between 5 and 6. By running an additional membrane or two I have found that I was able to process a little more sap per hour with about a 1-1.5% higher concentrate. My sap usually runs low around 1.3-1.5% so it is worth it for me.
Aquatech 8800 with transformer (comes with 3/8" and 1/4" fittings): $112.55
The model number listed for this pump is 8852 - please make sure when it arrives that it is in fact an 8852 and an 8851. The two models look identical but the 8852 has a higher flow rate and pressure.
10" water filter housing 1/4" in and out: $8.00
https://www.wateranywhere.com/1-4-in-out-white-white-flat-cap-10-filter-housing/
1/4" fittings for water filter (you will need two of these): $2.00
https://www.wateranywhere.com/1-4-34-t-8211-1-4-34-m-st/
Water housing wrench: $4.50
https://www.wateranywhere.com/filter-housing-wrench-for-standard-10-filter-housings-black/
Membrane Housing Clips (if you will be mounting to plywood): you will need one for each membrane - $1.60
https://www.wateranywhere.com/single-clip-membrane-housing-to-bracket-1417/
Residential RO Membrane Housings (you will need four of these): $16.92
150 gallon per day RO membrane (you will need four of these): $43.86 each
I was able to find the membranes and housings on eBay for $39.99 from the seller - domesticwaterexpert. I am not sure how long this link will work:
If you are able to purchase this combined package you will need to order 3 of these fittings for each housing:
1/4" by 1/8" quick connect fittings:
https://www.wateranywhere.com/1-4-34-t-8211-1-8-34-m-st/
1/4" Outside Diameter to 1/4" Compression brass connector: $4.18
This is a brass connector that can be picked up at Homedepot or Lowes. It is for connecting a 1/4" outside diameter pressure gauge to the 1/4" tubing
Pressure Gauge: $10.99
1/4" x 1/4" quick connect tee: (you will need four of these) $3.00
https://www.wateranywhere.com/1-4-t-all-sides-union-tee-fitting/
these can be found at home depot or Lowes as well
http://www.homedepot.com/p/Watts-1-4-in-x-1-4-in-x-1-4-in-Plastic-Tee-PL-3003/100188178
10" 5 micron water filters (50 pack): $61.00 or a 25 pack for $45
If you buy them individually or in 4 packs they are 3 or 4 dollars each but by buying them in a 50 pack (they don't spoil) you can get them for a little over a dollar each your choice. You will need one for each 75-100 gallons of sap you process or I estimate 1 for every 1 1/2 gallons of syrup you plan on making.
1/4" polyethylene tubing: $8.50
this is available at Home Depot and Lowes - you only need about 25'
3/8" polyethylene tubing: $17.50
this is available at Home Depot and Lowes - you only need about 10-15' depending on how you set things up
1/4" x 1/4" brass needle valve: $10.00
this can be purchased at Home Depot or Lowes