I have some builders' sand hanging around in my yard, and I was going to use
it for drainage in some new pots I've bought today.

My dad however has advised me not to, he says that this sand contains lots
of chemicals which won't do plants any good, because it is building sand.

The sand has been outside in the rain for at least 3 years - does anyone
know if my dad's correct about this, and if so, whether the rain would have
washed the sand clean by now?

Even if it is full of chemicals, if I just use it for an inch-thick layer of
drainage material at the bottom of each pot, would it be OK?

Thanks in anticipation!

Andrew