It's not necessarily the ph of the water that you're worried about. Sure, it'd be good to start with a neutral ph, but the important thing is the softness of your water. Your grains will adjust the ph of your water to the correct range for mashing if it's soft enough. To have some peace of mind, you could purchase some 5.2 buffer, which works very well even for some not-so-soft water. Really light grains (like pilsner) have a harder time adjusting, but for most "regular" grain bills, you will probably be fine. If you want to know, just test your ph about ten minutes or so after dough-in.