I have a 75 gpd bulk reef supply RO system (5 stages prior to DI). I purchased the 150 GPD water saver upgrade (another DuPont 75 gpd RO filter that takes the waste from the first filter). Water pressure is 60 psi. I totally forgot to get a proper flow restrictor with the upgrade. It’s a 550 built in with a flush valve. The output prior to DI is still just a trickle without any appreciable flow rate increase since installing the upgrade.
The current flow restrictor is a 550 ml inline built into the back flush valve they BRS sells. I’d think I’d need an 800 ml restrictor for 150 gpd. If I use this setup, will I lose membrane efficiency since my pressures are marginal
I wonder if I am just wasting my efforts with this water saver system - I’m not sure how I can keep membrane efficiency with this kind of setup. I would seem a better idea to run two membranes completely in parallel with restrictors at each membranes waste, with a pre membrane boost pump to be able to get additional flow.
Or should I consider a pre boost pump with this my marginal water pressure?
Please help educate me. Thanks!
I run 2 AMI 150GPD membranes in parallel at 85 psi and I use a 2:1 ratio flow restrictor ,for a 150 GPD membrane that is 800 ml.
Flow restrictor size can be confusing. You have to understand that when you are dealing with RO systems everything is based on psi to the membrane.
A 150 GPD membrane at a 1:1 ratio would be using a 400ml flow restrictor. The sizing is based your specific water TDS and chemistry. If you have 500 TDS water and you want to run a150 GPD membrane with a 400 ml FR you can but your membrane will scale faster than if you use a 800ml 2:1 ratio. The ratio is waste water parts to permeate (RO water) parts.
When you run the membrane at higher than 60 psi you create more RO water tegardless of the restrictor size.
At 85 psi , dual 150 GPD membranes and using a 800ml flow restrictor my system makes almost a 1:1 ratio of concentrate to permeate. I use softened water that starts at 260 TDS though.
Running two 75 GPD membranes in series will save water because you are running the concentrate through two membranes and extracting twice the volume of permeate for the same given volume of water you are starting with But the second membrane will take a harder hit because the concentrate will have a much higher TDS after it passes the first membrane. I wouldn’t run dual membranes in a series or parallel without a booster pump. My house pressure is 65 psi and I wouldn’t do it at that pressure but you could if you wanted to based on your specific water conditions.
Using a bigger size flow restrictor helps to make your membranes last longer.
3 or 4 to 1 is the rule of thumb for most membranes for optimal lifespan and water quality output.
I can make 20 gallons of 4 TDS permeate in about 2.5hours and that’s with 67 degree water. I run a 5 micron AMI sediment filter , catalytic GAC and a cto plus carbon block from matrikx. That 4 TDS is from both membranes combined so each membrane is taking my starting tds water of 260 down to 2 . 99% efficiency without a sweat.
You can use your 550 ml FR which is roughly slightly higher than a 2:1 ratio for a 75 GPD membrane. Two 75 GPD membranes don’t equal a single 150 GPD membrane , it doesn’t work like that . You are still using 75 GPD membranes. But you are doubling the production of water for the same size membrane .using an 800 ml FR on a 75 GPD membrane would be a 4 to 1 ratio and actually increase your waste water not save it. A bigger flow restrictor would be easier on your membranes but will lower permeate production unless you increase the pressure to the membranes.
i use an 8800 aquatech with an auto flush valve that has NO FLOW RESTRICTOR in it and a 40 psi pressure switch to shut off the pump. I use a 60% ASO valve with my waste water line plumbed through the high side so it shuts off right. I also have lines going to a separate tank for my fridge and ice maker, a line for my RO reservoir and a separate line to fill my 5 gallon water cooler jugs. I had to adjust the pressure switch to get it to shut off the pump as soon as the tank was filled but other than that it was pretty easy to put together. I don’t reef yet but will be adding my DI stage at some point when I decide to do it. I have naturally breeding cichlid tanks thanks to my RO water. I don’t drink sink water and I would never put my fish in it either!
make sure you get yourself an in-line tds meter and a pressure gauge as well.
i buy my equipment from buckeye hydro. Check out their site. Good prices and lots of info as well. The membranes I use are made by AMI out of California. They make the membranes for HydroLogic RO systems. The 150 GPD membrane I use is $25-$30. I could run a 1:1 ratio if I wanted and not care because the membranes are so cheap anyway. I’ve had mine for 3 years already.
let us know how it works out or if you have any questions. RO systems can drive you crazy and learning things on your own will cost you a lot of money and wasted time in a hobby that’s already expensive enough!
