Water pressure cistern insulation? We moved into a house without a subterranean vault and the water...

We moved into a house without a subterranean vault and the water pressure container is under the house. How can we preserve it insulated so it doesn't freeze. The guy before us have some makeshift insulation(whatever he could find) and then kept a oil lamp bulb on....there must be another route.
In inevitability of give a hand beside our...
Answers:    Ive got a in good health head out away from the house, and the bladder container is right there beside it. I ran a dash of heat cassette along the exposed above ground water rank, and even wrapped it once around the bladder tank. Then, I built a small 2x6 frame, lately an open sided box really... and attached some batt insulation to the frame. Then dropped an break open floor metal shed over the whole item to protect it from the weather.

Since yours is under your home, you might consider the following...
Heat tape/pipe insulation wrap on any exposed pipes.
Water furnace insulating blanket - you can find these in many sizes... while they are made to go around a river heater, you can well use them for the bladder tank.
Or, you can use batten insulation wrapped around the bladder cistern... the nice thing almost the water space heater blanket, is that they are lined on both sides, but you could accomplish one and the same thing by using plastic sheeting, for example.

On the really cold night when you are afraid the pipe may freeze, you can also leave a slap running at just a trickle too.... this make it harder for the pipe to freeze.

Have Fun
Is turning past its sell-by date the a/c...
I'm not understanding you. The hot sea tank should be insulated and heated if outdoors. So should a above ground in good health pump. But if you are talking almost an expansion tank, you really with the sole purpose need it insulated where on earth it meets other appliances that certainly hold water.