Have you tested your tap water for PH? Test your tap water's PH right out of the tap, and then let it sit out for 24 hours and test it again. My tap water is 8.2 out of the tap; after it sits out it settles down to 7.2 which means for water changes I need to let the water sit out for at least a few hours (an air stone helps to get the PH down faster) before putting it into the tank.
The PH change shouldn't cause cloudy water. Have you changed filters? Is it a new tank? Are there fish in there?
If it's a new tank with fish and you didn't cycle it before hand, read the link in my signature that says "new tank with fish;" also read the one that says "what is cycling."