[MNWC]

You're using the wrong pump.
You need a Booster Pump, something like this works great with 30psi + mains water pressure and will give you 100 psi at the membrane or less (80 psi) if you wish by tweaking the waste valve:
https://www.machinemart.co.uk/p/cbm240e-1in-multi-stage-230v-booster-pum/
And you won't need to use any break tank just straight off of the tap.

Just checked the psi and flow from the tap that i use.  psi is 39 flow is about 8 litres per minute
Would that pump you quoted be ok for this ?

[andyM]

Yes.
My tap pressure is 30-35 psi and with the Clarke cbm 240 pump going through a Fibredyne pre-filter and 4040 HF4 it produces around 200 ltrs per hour.

[Spruce]

I would be rather interested to know what the outcome of this is.

I use that pump as a transfer pump. I wouldn't have thought it would work as a booster pump even connected to the mains.

[Spruce]

You're using the wrong pump.
You need a Booster Pump, something like this works great with 30psi + mains water pressure and will give you 100 psi at the membrane or less (80 psi) if you wish by tweaking the waste valve:
https://www.machinemart.co.uk/p/cbm240e-1in-multi-stage-230v-booster-pum/
And you won't need to use any break tank just straight off of the tap.

Just checked the psi and flow from the tap that i use.  psi is 39 flow is about 8 litres per minute
Would that pump you quoted be ok for this ?

I see Daqua.co.uk use a smaller booster pump on the 4021 r/o. See his video on his site.