any plumbing engineers out there that can advise me?
I have a bar mixer shower fed from a twin impella pump and get crap flow from it.
it was installed by previous owners and it's never been great, but flow rate got stupidly low about 2 months ago, and after checking the pump was ok and the hot/cold feed was good I put it down to a failing wax mixer cartridge so bought a new cartridge (old one was plastic, the new one is brass). it now takes ages to get upto flow (a couple of minutes) - and I'm guessing that's just the quality of the cartridge?
but the real issue is why can't I get a good flow rate?
the cold water header tank sits about 1mtr above the hot water tank. the hot water tank sits on the floor, with the pump sitting next to it on the floor. the mixer unit sits about 1mtr above the pump/floor.
any suggestions?

