Pipe Noise from Well Pump

I am trying to solve a problem with my well pump and house pipes. When I am watering outside and the well turns on, it gives a little kick in the hose. At exactly that moment the pipe under the house makes a loud thunk.
The well has a pressure tank, and they are 100 feet behind the house. This mostly happens when I am watering beyond the well, so I am 150-200 feet away from the house.
I have tried to hold onto the pipe under the house, which is suspended with hangers, but I can't stop the noise. Any ideas?
Thanks.

If this is a submersible pump, the problem is probably with the check valve(s). There should only be one check valve in the sytem, located right on top of the pump. If you have another check valve up top, remove it and the "thunk" will go away. Although the extra check valve maybe masking the real problem, which is your down hole check valve is out or leaking back, or a hole in the drop pipe. After removing the above ground check valve, if the pressure drops when no one is using water, you have a bad check or a leak in the pipe down hole.

A lot of people don't think an extra check valve in the system will hurt anything. But this is exactly what happens when when the bottom check fails or even leaks back a tiny amount. It is not if, but when this will happen. It is much more obvious on larger pump systems, but happens on all pump systems.

Another possiblity is that you have too much air in your bladder tank, and the bladder is hitting the bottom just as the pump starts. If this is the case the extra air didn't get in there by itself. It would mean the bladder in the tank is bad and the extra pressure is caused by the water getting on top of the diaphragm.

Thanks for your great information! Yes, I have a submersible pump. There was no extra check valve in the system. But I isolated the problem, finally, and discovered that the water pressure gauge was not reading correctly. After replacing that and getting my true pressure readings, I reset the pressure tank pressure lower and adjusted the cut-in pressure on the pump regulator to be 2 psi greater than the pressure tank pressure. The knock went away!
Now I will keep a close eye on the pressure tank pressure to see if it rises. If it does, then I will replace the tank.
Thanks again.

Grateful Dave.