Tech info
Hi energie,
First of all, may I suggest you borrow or buy and read a copy, either of the user manual for any aeroplane you fly, or a copy of one of the not-bad third party manuals, when you commence to convert onto it. That will enable you to ensure that you are fully acquainted with the details of the aeroplane at an early stage and make your familiarisation on type much quicker. The manual should be available to users at your club or FTO.
There is definitely quite a good third party manual for the C152 and it's cheap and currently in print and easy to get. The fuel system is fully described.
Metal parts of fuel systems are prone to internal corrosion, hence the sediment.
Fuel is hygroscopic, so it absorbs moisture out of the air in the tank. Fuel filler caps both on the storage bowser and on the aeroplane can be an imperfect fit and there is the potential for rain to get in, admittedly in small quantities, but these build up.
It takes some time for water to settle to the bottom, so if you refuel from a recently recharged bowser with water in suspension it will take perhaps 30 minutes to settle out, hence the need to check the fuel at the various bleed points before you fly.
If you have an instructor whose drinking interfers with his/her job, dump him/her NOW!.
I don't know much about the details of the pipe runs in the C152: you can look these up in the manual. As I recall, its a gravity feed to dual fuel pumps.
You have to prime your engine for the same reason you use a choke in your car. A cold engine starts much more easily on an extra-rich mixture, but you don't need the extra-rich mixture once the engine is running.
Anything I haven't dealt with here is in the manual; 'hope this helps.
Broomstick.