Sizing flow meters

[MarquisVII]

Hours of reading on this forum and I still haven't been able to extrapolate exactly what I'm looking for, so here goes...This is for a single post XLE-4040 with 240GPH Procon, 1.5HP motor and a 1500GPD Wayne feed pump. Of course I should have a 330 to begin with, but I scrounged this build together in a hurry for less than $1,000 with the big savings being the pump ($90) and the motor ($80). So it's what I'm working with for now. I may move up to a 330 in the future, but keep in mind a 4040 is already overkill - I'll have max 75 taps on vac.I'm not sure which flowmeters make sense. I will have recirc line. So I was thinking .2-2gpm for all three meters. That's 6gpm capacity for a 4gpm pump. What I don't know is how much flow I can expect out of each of the three branches. I know a meter on the recirc line isn't necessary, but seems like good practice for overall monitoring. The method I envision is batch processing concentrate back in the sap tote until maybe 8% and then redirect a final pass with the concentrate heading to the evap head tank at maybe 10%. Potentially related question: Will the pressure I run at affect my meter choice? This motor could run the 240 Procon all day at 250psi without breaking a sweat, but is it a bad idea to run that high with only 4gpm going through the membrane? Am I better off staying around 200psi?

[bmbmkr]

You don't want your flow meter to restrict flow when you have the concentrate valve wide open at start up, and especially when you are rinsing. A smaller flow meter will give you more accuracy because the more graduation lines, which is good, but the smaller flow is restrictive, which is worse.

With a 240, you are looking at 4 gpm total, a single 4x40 can put out 2 gpm of permeate if the stars are aligned and everything is perfect at 300 psi. The downside is, your membrane is designed for around 8-10 gpm, with a max feed of 14 or so depending on the mfg. 4 gpm is not enough flow to keep from plugging, even with your re circulation line. You will only be running for an hour or so with 75 taps, so you won't worry about plugging several times and having to rinse or run warm water through in the middle of concentrating, but the over kill part is, you may not make enough permeate to rinse and wash your membrane. You might look into a 4x25 membrane and vessel. you want at minimum 100 gal of permeate to rinse your membrane when finished for the day. Soap and acid washes, add to this. It will work, and believe me I understand the budget part, but it isn't optimum. Oh and you only need 2 flow meters. I did put one on my recirculation in one of the iterations of my home build, but ended up taking it off, After running several 330s and a 660 for the last few years Procons are spot on, positive displacement pumps, even at pressure, so if you want to know how much you are recirculating, just subtract your concentrate + permeate from your pump. The less plumbing joints you have in an RO the better, even on the low pressure side. you WILL have a leak or two here & there to fix. don"T USE TOO MUCH thread tape, more is not better!