mikeikb,

In Ottawa I can't find generic 6% bleach. Walmart switched to 4% and the other no names are 3% to 4%. The best deal I have found is at Canadian Tire, where they sell a 5 litre jug of Aquarius Liquid Chlorine for $4.69. It is 10.8% sodium hypochlorite, same stuff my pool stores sell for $7 to $9. CTC also carries Purox for a buck more, but it's the same stuff, you are paying for the branding. Just note that sodium hypochlorite is bleach, the only difference between it and "pool chlorine" is the concentration - less jugs to haul at 10.8% vs. 6%.

Ben is indicating 4 US gallons at 6%, which would result in adding about 13 ppm.
According to bleachcalc, you will need 8.4 litres @ 10.8% to achieve that for 70,000 litres. 2 jugs of Aquaris will give you a bit over 15 ppm, which would be fine.

Our local Walmart does not carry the HTH 6 way kit. Worth checking the Walmart in your region, though we don't even have the OTO in stock now as they are clearing out the summer stuff. You may to go to a pool store for the OTO kit. At that level of chlorine, the test should be showing dark yellow if not brown, which is fine.

The bleachcalculator is here:

http://www.poolforum.com/zxq/BleachCalc262.exe