well yes but with 50-60 should be getting better results I'm led to believe
What 4040 have to got? Champ or Vyair housing? How long have you had this 4040 and has it always been slow? If not, when did it change?
If you disconnect the hose from after the prefilters, do you have a good flow of water through the prefilters? Do the prefilters have 1/2" ports?
Is the 4040 membrane correctly inserted into the housing?
Install membrane into champ pressure vessel:Remove the end cap from the feed end (the end with only one port) –
this is achieved by pulling on the white tab which will remove the white
holding ring. The end cap can now easily be removed. Remove the
membrane from its packaging. Insert the membrane into the housing
with the black brine seal at the feed end (ie feed the membrane in with
the brine seal end going in last). Push the membrane firmly to ensure it
is fully inserted. Push in the end cap, again ensure it is fully inserted to
reveal the holding ring groove. Replace the holding ring.
(The brine seal is the seal at the end of the membrane.
http://www.wateranywhere.com/index.php?cPath=22_444This web page should help. The 4040 membrane is the 4" one pictured left hand bottom corner.)
Are the connections fitted correctly? (On the champ housing you have one port on one end and two ports on the other. The end with the single port is the inlet from your prefilters. The other end is the pure and waste ports. The pure port is at the top in the center and the waste is on the side opposite the inlet.)
Here's fitting a 4040 membrane into a Vyair filter
https://www.youtube.com/watch?v=iP0t25qn7HM