Regarding the booster pump .I’m not interested in increasing the amount of water it produces . It does more than enough . Just wasn’t sure if it makes the membranes more efficient or less waste .
I have a 4040. Our water pressure is 50psi and when I last tested our delivery at the tap it was 13lpm of water. I have never run a booster pump but use an HF5 Axeon membrane. My r/o uses 4lpm of tap water.
I have my r/o set-up at about 55/45 waste/pure and that is the best ratio (sweet spot) for the system as it produces the lowest tds of pure from the r/o before di.
If I open the waste more so have a ratio of around 2 waste to 1 pure my pressure gauges drop from 50 to 45psi and my rejection rate is similar. If I further open my waste tap to say 3 to 1 then the pressure on the membranes drops to around 40psi and my rejection rate goes up.
Our tap water tds is 123 atm. I checked it this morning. The tds of the pure leaving the r/o is 3. If I use a ratio of around 3 to 1 then my tds goes up to 4 or 5ppm. These aren't big numbers, but they are big percentage wise.
I've run my r/o like this for the last 8 years and that's how old my membrane is to the month this month. Yes, with time, membranes will wear out. (My rejection rate has dropped from 98% to 97% over the years.) But the biggest issue we all have is chlorine, as chlorine destroys the fabric material the membrane is made from. If your r/o is consuming more water than necessary, then your carbon block is going to have a shorter service life. This will have an effect on the membrane's longevity if it stops removing the chlorine from the water.