Danilada
What your doing is creating a major problem.
No glass flat window glass is made here in NZ.
The recycling depot is for bottle glass and it is made totally different to window glass that tanks are made from.
By tipping window/flat glass into the bin, your effectivly making useless, the great efforts of people trying to recycle bottles.
It is quite simply dumped as land fill.
A few years ago, we could (Glass Merchants) firstly sell and then later give our glass off cutts (if totally clean) to the people that make pink batts but now it costs more to ask them to take it than it does to dump it.
Simple thing is that we glass merchants have to pay to have it dumped at a cost of about $75 per cubic meter.
If your father asks his suppliers he will find that what I have said is 100% correct.
To dump old tanks or in fact any flat glass, phone your local glass company and ask if you could dump it in their bins but as mentioned, it does cost them