25L in 3 hours is about half the amount you could be getting from the system.
It is all about water pressure, if you can get the pressure up you will produce water faster, the TDS in the water will be lower, and you will have less waste.
You could check to make sure all the mains pipe taps are fully opened, the ones that supply your feed tap. Failing that a booster pump is an option.
If you are happy with the amount you produce, in the time it takes to produce it, then carry on the way you are. If in the future you need more water, or water faster, then add a booster.
Peter