You answered you own question: at freezing.
At or near 32 degrees F your pump should be turned to keep water moving. moving water doesn't freeze.
It is important that any exposed pipes, filter and pump have moving water at freezing as this water will freeze first and cause the item to crack. That's expensive as compared to the few cents it costs to operate the pump.
Water starts to freeze at 32 degrees. So it best to turn pump on at approx. 35 degrees & leave on until the tempt. rises to 35
At least one degree above freezing?
I would seriously consider turning it on at 0 degrees Celsius.
you have to have good insulation wherever you have the pipes in your house or apartment. This will keep your pipes from freezing and bursting. :)
There is no single best way to keep pipes from freezing. Insulating (wrapping) pipes is a common method. Leaving the cold water faucet open just enough for a slow drip is another method to prevent freezing.
No, it won't help at all. You need to keep the pipes above freezing temperature (32oF, 0oC) and if it happens often (like for more than two weeks a year) you should invest in insulation.
insulation in the wall
Usually above freezing, and keep the caulking from freezing also.
Fill with anti freeze solution or keep the water running.
by keeping your pipes above 32F degrees and to do this is installing heat tape and insulation around your pipes or just insulation if your climate isn't so cold.
A lot of times the flow from dripping faucets actually prevents the pipes from freezing up.
You must keep water pipes from freezing because when water is cooling to the point of freezing, the particles contract. But eventually when frozen too long the ice expands, not melting but expands which can damage the actual pipe.
Wrap them in insulation and keep the water flowing through them at all times. If electricity is available, they can be wrapped in electrical pipe heating tape to keep them above freezing temperature. Insulation over this tape will still help (if the manufacturer of the heating tape indicates it is OK and won't cause overheating).