Ro/Di Running Slow???


New member
Hi I have a 150 gpd ro/di bwi 5 stage system I recently changed the sediment filter and the 2 carbon blocks as well as the di resin..The Membranes are 2 75 gpd membranes and the bottom one is a year and a half old and the top is 6 months old..I have a brand new one as well but I think the others are still good ..When I first bought this system 6 months ago or so it was working at the proper speed no it seems to be running very slow like it take almost 6 hours to fill up a ten gallon bucket or longer??? I back flush the membranes every time I use it for 5 minutes before and after...Does anyone have any ideas why this is running so slow??? And what I can do to bring it back up to par??? Any help would be much appreciated


New member
Occasionally I have a similiar problem. I found that when I open and close the valve where I tapped into the house water line it speeds up. My guess is that maybe I'm getting a calcium buildup around the needle. In short, make sure you have good flow of water into unit.


New member
If the problem started right after you changed filters I would check to make sure they are all seated correctly and nothing got stuck in the tubing while you were doing a change.


New member
ok I will look into everything u guys suggested and get back to this post tomorrow Thanks for the help everyone


1. Check all connections for leaks. Check each RO membrane "Individually" for flow if you can.

2. Use a pressure gauge before the RO Membrane to tell you what the entering pressure is. At least 40PSI is ok.

3. Use your Flush Kit to get the crap out of the Waste Line. Junk will build up inside there over time. (I know you said you do this)

4. Make sure you are using 1- "75 GPD Capillary Flow Restrictor" for "Each" RO membrane (2 total) or at best an inline precision Adjustable Flow Restrictor (Needle Vale) to have the correct back pressures for each membrane. Rule of thumb is 4:1 Waste to Good Water made at around 40PSI and 78 Degree Water.... (If I Remember Right)

5. Add 1 if not 2 Dual in line TDS meters to tell you what your RO\DI Unit is doing.

TDS Test points are:

Before Sediment - Optional
Before RO Membrane - Required
After Membrane Which is Before DI Resin - Required
After DI Resin - Required is a great place to get what you need and Russ is the man you want to ask for help.

Good Luck :)


New member
Did you rinse the carbon filter well before connecting it to the membrane part? They can have carbon dust in them that can clog membranes.