Of course, if you have to replace the laterals, then changing the sand is probably necessary.

How much does the N2 cartridge cost you each year? Is it $100 or more? I buy 25 gallons of 12.5% for $95, which is more than enough for a season. I would need to use twice as much and the N2 would have to cut that in half to break even.

That's my argument.