I'm renovating an existing house which I don't yet live in. The bathroom was just redone (including new pipes) by a professional plumber. There is quite good water pressure in the sink, light pressure in the rain shower, and just a very slight trickle in the shower and bathtub. The plumber says the pressure is too low, and suggests a water pressure tank. Note this is in the Philippines.
I've included a diagram of the plumbing below.
Is it likely that the lack of water in the shower/tub vs. the sink is just low pressure due to the additional elbows in the pipe going to the shower/tub (8 elbows) vs. to the sink (5 elbows)? How can I estimate the additional pressure required (and thus whether a pressure tank will help and what I should get)?
Thanks for any advice,