Monkey... When you say sand pit what do you mean exactly? Is it a natural source or has it been dumped there. I'd be cautious of using sand from a field as it could be possible some sort of ferts or pesticides could have been in contact with it.
The sand I used to use in all of my tanks was nothing more than play sand you can pick up at any lowes or home depot. I personally have never had a problem with it and have used it with both freshwater and saltwater for over 10 years.
I currently use a sand/gravel mix I get from the bottom of high flow areas in local mountain streams. I'm very fond of the look it gives, very natural, and so far haven't had any problems with it whatsoever. It did at first concern me that it could have come into contact with something I don't want in my tank, other than the caddis fly larva I get with it. I'm hoping that the presence of trout in the stream and water pennies speaks for the quality of the water and what's in it. Like I said though... I haven't had a single problem yet.