Unit?

the unit (if it makes a diff) is an RO filter...I believe it requires about 45psi and at the location (near where the water enters the house - before many smaller pipes and the flow is decreased) I currently have a flow rate that seems to be much higher.?..I want to lower it so that I can use this filter...

Flow rate and water system pressure are two entirely different things.

I'll assume you're on a municipal water system... what is the static water pressure in the house water system now?

Is this RO a small POU 4 or 5 stage or a whole house RO?

Hi justalurker (or other),
ok...I understand now that flow rate and system pressure are two diff things...Ive read that "static pressure can be measured using an aneroid, Bourdon tube, or a mercury column", but I dont have any of these. Can I determine my homes static pressure in another way?...I am on a municiapal water system (in NT NY if that helps)...the RO unit is prob rather small (meant for a large fish tank and not a whole house)...

you can buy a pressure guage from HD or Lowes. It connects to a hose bib.

You are making a far bigger project out of this than it needs to be...

As I understand it you will install a POU RO (same as an undersink unit) to supply a fish tank.

IF, you choose the unit wisely it will operate with no problem with supply water pressure from 40 psi up to 100 psi.

If you want to learn about ROs L@@K here

You can check your plumbing system's static water pressure with,,, an INEXPENSIVE pressure gauge that screws onto a hose bib. They are available at almost every big box store.