bending polypipe through right angles

[shardy]

hi all,
I wondered if its advisable to bend polypipe through a right angle or would it be better to use elbow joints?
We had a loft conversion done and the plumber used polypipe or a similar product throughout and there are 3 different locations where the pipes bend through a right angle.
I should've asked this question ages ago as two of the locations where the pipes are bent are no longer accessible.
Yesterday, a few months after the loft plumbing was done, our pipes elsewhere in the house started screaming and vibrating. We have been here 10 years and never experienced any problems with pipes. Usually the noise happens when a tap is used anywhere in the house, or a toilet is flushed. But sometimes it happens spontaneously. Also water comes out of the old first floor shower even though it is not switched on. Switching the shower on and off briefly stops the pipes screaming and vibrating.
I have read online today that bends in pipes can contribute to "water hammer" and elbow joints should be used instead.
Or is it likely just to be an air lock or dirt in the water pipes somewhere?
Thanks in advance for any advice
s

 

[oilboffin]

You could Buy a Plastic former for polypipe to give a 90degree bend

 

[BigSnoopy01]

poor install, not enough clips, no lagging etc.... prob not the reason you have noises. more likely a tap or float valve causing the noise.

 

[shardy]

thanks BigSnoopy. The old shower seems like its on its last legs. I'm guessing its that perhaps rather than a tap. Its been leaking slightly for some time.