you should check for metals ...

you should check for metals in water

If your water is coming out of the ground with a pH of 5 you may have other issues you should be worried about.  A pH like that could indicate reducing conditions and there are certain harmful metals that are more likely to be in solution in such water (i.e. arsenic).  Raising the pH might mitigate these concerns but you should know what is there first.  If you haven't already you should collect a sample for typical metals found in groundwater.