Firsr time post apologies if it's been covered. I had a mega flow system fitted 9 months ago and if I'm in the shower for example and flush the toilet the pressure drops. Same if I'm running a bath and turn the kitchen tap on, the pressure drops quite a lot. I had a total house renovation and my builder is scratching his head and saying it's just how it is. But I know that it's not. Any tips and suggestions would be appreciated.