water pump capacity

[badflash]

Multiply 1700L/Hr times 2 and that is the minimum. You need a safety factor of at least 50% so multiply by 3. That assures that when plumbing gets a little fouled you'll still have enough flow.

I understand it means times two but Im woundering how it relates to the 1700L/hr? are you talking about the fact I am cycling twice in one hour?
What pumping volume (litres) per hour would you recomend when I go to purchase a pump?

Thanks for your input this.
Bruce