Hi Andy,
I'm not a builder and can't answer the chemical side of your question.
However, most gardening experts agree that builders' sand does not promote
drainage as the particles are too small and smooth. Sharp sand or grit is
usually advised.
A modern and usually free (recycled) drainage medium is polystyrene, as used
in packaging. It has the advantage of being very light and clean. Again, I
don't know if there is any chemical leakage. However, most ornamental
plants seem happy with it, but be cautious of planting vegatables with it if
you're worried.
Spider
Andy Hunt wrote in message
...
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