A small amount to keep the pilot light going.
Spillage excessive condensate bad thermocouple draft
Thermocouple. Keep pilot knob depressed for 30 seconds after lighting pilot.
Spillage
My direct vent furnace pilot light issue was the glass viewing port was missingallowing room air to blow out the pilot light. Replacing the missing glass which stopped the draft, fixed the problem.
The thermocouple is going bad. The thermocouple is the small tube that sits in the flame from the pilot light and goes back to the gas valve. They are easy to replace and cost $6 to $8. For health and safety the failing part should be replaced without delay by a competent gas engineer.
No because water heaters have a safety valves and when the pilot light goes out the safety valve shuts off the gas
If it is windy outside, you may be getting just enough of a breeze to blow out the pilot light -even though the covers are shut. My heater is in the garage, and even w/ the garage door shut and the covers on the heater shut, very windy weather can still cause enough of a draft to blow out the pilot. You could try to find something to block drafts around the heater such as a hot water heater blanket.
No If the hole is smaller then the diameter of the supply line
A number of problems can cause a swimming pool heater not to work. The most common I have found is lack of water flow. A heater needs a certain amount of water flowing through it to work correctly. The next most common problem is due to the pilot not lighting or remaining lit. This is usually due to the pilot generator not working. When you light a pilot light and have to hold it for a length of time before releasing the button you are allowing the pilot generator to heat up and then stay open to keep the pilot lit. Usually you need a licensed person to do work with changing items on a gas unit. The thermostat can be a problem for any water heater. Most of the heaters I have worked on were gas. If you have an electric heater waterflow still needs to be checked and the electrical connections can become corroded in the presence of chemically treated pool water.
You can turn it down so that it doesn't come on much. If it is a gas heater, the pilot light might provide enough heat to keep it from freezing, but that is not certain. If there is not going to be any heat in the building, the pipes need to be drained, the heater also and anti freeze put in the drains and the toilet. This anti freeze is different than what is used in cars.
Check your instructions, Usually you have to keep it on pilot mode for 30 seconds then you should be able to turn it to on without the pilot flame going out.