Hello nailed,
One quick word, design it in detail before you buy anything.
Understanding your options allows the best design choices, keeps your options open.
I see many regrets here. Wish they waited until they understood.
You have an 8" pipe with 25' head, which is over flowing. Any way to get head larger?
Looking at some charts that is >300gpm. Lots of water!
Please do a flow study to verify the numbers. How does the flow change over the year? Do you have a winter? Design must consider this.
Power is >1kw. Sweet! Please check the numbers, getting late:-)
>24kwH in one day. Not quite enough for my house 31...
I do not know if your grid tied or can use net metering. (more options)
Hydro is very steady, well suited to using induction motor as a generator. 2-3 HP induction motor is much cheaper than an equal axial PM generator. Induction motor makes grid connection system easy. May need a back up load if the power fails. Resistor bank and excitation capacitors needed.
How far is the system from your power use? Determines what voltage you should be using. Power losses in the power lines.
Common Hydro turbine choices are:
Pelton - difficult to make yourself. 25' is considered low head. Lose some efficiency.
Banki - Easy to make, little more difficult than a water wheel. Plastic works, 25' is in the power zone for this puppy, efficiency is good for low head. If your good at building stuff, I would consider this your first option, could save you couple grand. Someone just built one out of metal, Plastic would be much easier. Gives you a chance to learn about it.
Other turbine designs exist. Like Turgo impulse an improved Pelton, as difficult to make.
Banki turbine also called the Michell turbine.
You have an exciting situation. Study it well, you will be happy with the outcome.
Have fun,
Scott.