Supplyhouse.com is really good for all your fittings. US Plastic or Zoro for your food grade high pressure tubings. If your going to do anything stainless buy Merit brand not bluefin. Import fittings suck at high pressure. Freshwater Systems for your flow meters. Depending on how you plumb it, you can get a rotometer (5gpm) with one or get a needle valve from Supply house. I would suggest modeling your build after the RO Buckets 2 post, very simple and near bullet proof.
Hillcrest Maples
2024- 200 on Guzzler, new home built 2 post, SL vac filter
2023-100 on Shurflo, new 2 Post 4x40 RO Bucket
2022- 150 on Shurflo, new 16x36 Sugar House and 18x48 Vision, Dual RB 25's RO's
2021- 150 on Shurflo, home made arch under 18x40 cdl pan, RB 20 RO
2020- 99 On Shurflo home made arch under 18x40 cdl pan
2019- 10 buckets, steam pan on grill
2018- 5 spiles into milk jugs, stove top, caught the maple bug hard.