Hi Simon. Service life of 11250 liters if it's UK gallons. USA gallons = less.
I'm sure there are arguments for and against everything. Because our water is full of sediment, I have always used a sediment filter first, then c/b.
I could see an issue using a booster pump after the filters but before the membrane if the filter clogged up with sediment quickly and 'starved' the booster pump. I believe the best place for a booster pump is between the prefilters and membrane. But if I was to fit a booster pump, it would be before prefilters because I don't trust the quality of our water supply.
If you are an old Merlin or prf r/o user, then the Fiberdyne filter is a sediment filter as well. There was a window cleaner near us who had a Merlin. He purchased a 10" prefilter housing and fitted a sediment filter in it before the r/o. It saved his Fiberdyne filter on several occasions.
A sediment filter on my r/o once lasted 1 day. It wasn't unusual for me to replace a sediment filter only twice before replacing both on the third time when the c/b was due replacement.
It could well be that my carbon block filter could last much longer than 75600 litres before being replaced. I don't know how much chlorine is still in our tap water at any given time.
However, I do know that a carbon block filter won't last a year before being changed on our water supply. The first r/o I bought was 2nd hand from a local window cleaner and was 1 year old. He had never changed prefilters and the membranes were 'shot'.
You have to do the math regarding changing prefilters later and early membrane replacement. It's all to do with economies of scale and what works for you. Once a membrane starts to become less efficient, the amount of resin you use to polish the pure off will increase, so that has to also be considered. And we know how much resin has gone up in price recently.
This is just my opinion.
