A: The max GPM flow rate is 2.5 gpm (gallons per minute), if you using the water economizer, the flow would be more less, that would be save of water.

Yes, Shower head come with a filter that can be removed to cleaning. The filter is made of stainless steel mesh prevent clogging for consistent performance and longevity.

No it doesn't leak. Water falls soft and smooth. But it is a bit heavy for the extension I purchased. I have to really tighten the T's with a wrench.

The diameter of the round shower is 12 inches, with 144 water spouts; the side length of the square one is 12 inches, with 100 of water spouts.

The shower head working with all standard 1/2'' pipe threads. easy to mount on the wall-mountedor ceiling-mounted shower arm. You just need to take the old shower head off, then turn the new shower head counterclockwise. come with a mini wrench is also attached in case you are lack of strenth to tighten.