Dealing with the everyday mechanical tasks involved in managing your pump can be confusing at first. These mechanical aspects of pump therapy will soon become "second nature" to you.
Priming is done to purge the newly connected infusion set tubing of air. For MiniMed pumps, priming ensures that the pump motor driver arms are seated fully against the reservoir plunger. For Disetronic pumps, priming also ensures that the piston rod is seated firmly against the insulin cartridge plunger to guarantee consistent, accurate delivery.
Once the infusion set is primed (for example, after changing an infusion set, cartridge / reservoir) it is usually not primed again until a new infusion set is attached to the pump, when the cartridge / reservoir is changed, or when you need to clear the tubing of a large bubble :-(
When you disconnect temporarily for shower or other activity, it is not necessary to prime the infusion set again, since the tubing already contains insulin. However, before I re attach my pump, I will often bolus .5 or 1.0 unit before re connecting. This is a convenient time to check to see that insulin is flowing out of the tubing end, and everything is working o.k..
DO NOT PRIME THE TUBING WHEN IT IS STILL ATTACHED TO YOU. THIS WILL RESULT IN A "SERIOUSLY LARGE" BOLUS, WHICH IS NOT SOMETHING YOU WANT TO DO ACCIDENTALLY!!!
If you are disconnected for a period of time, it may be necessary to bolus a small amount to make up for the basal insulin you missed while you were disconnected. The timing and amount of this adjusting bolus will vary among users. It will take some experimenting to discover your limits and ranges.
The MiniMed Silhouette (also PureLine Comfort / Disetronic Tender) infusion sets ship with a small clip which is designed to snap into the cannula base (part which is taped to you) when you disconnect for showering or "whatever". This protects the cannula portion while you are disconnected and prevents stuff from getting into the end of the cannula base. There is another plastic piece which clips to the tubing part of the set while disconnected and protects it.
If you placed this clip on the portion of the set which is attached to your body, you should be able to bathe with it and not worry about water getting in. This part of the cannula base also tends to seal itself when you remove the tubing end. I view this as a one way "fluid lock". The seal does not allow anything to flow in or out of the seal until the tubing is connected again.
For "Quick Release" sets such as those offered by MiniMed, there is a rubber "stopper" which is placed over the needle portion of the Quick Release mechanism while disconnected. This protects the needle from contamination.
Most of these sets work just fine for showers, but I'm not a bath guy ;-) If you are a "soaker" who sits for an hour or so in the tub, the adhesive on the tape can start to loosen.
In addition, sets with "pigtails" on them, such as the MiniMed Quick Release sets, should be protected from prolonged exposure to hot water. Prolonged exposure to hot water will result in the distillation of the insulin which remains in the tubing. Insulin affected this way will frequently lose its effectiveness.