Well, I guess I just fixed.
Yes, the load uses up to 25A, the system is designed for that.
The Arduino is powered with 12V supply, and regulated with LM05, and I'am using some 1000uF capacitor to filter and also decompiling capacitors 100nF.
I just added the snubber circuit in parallel with TRIAC Gate and A2, and is working fine, I can turn the load ON and OFF, and also power water pump in the same AC power line and no reboots.
Here is the updated circuit diagram:
https://drive.google.com/file/d/0B6GSACZaFHMfRDlUSEFjMEhBZzg/edit?usp=sharing