When replacing a shut off valve for one of our toilets, I had to sweat it onto the short length of copper tubing coming up through the floor. Had the water supply shut off to the house, but water was still slowly rising in the copper tube and wasn't allowing it to get hot enough. Buddy of mine that is a plumber told me to stuff bread down the copper pipe. It blocked the water long enough for me to sweat on the new valve, and then the water just dissolves the bread when the water supply is turned back on.
I told a guy about this trick a long time ago. The guy calls me and asked how long it took for the bread to dissolve.
Naturally I asked how much he put in. 1/2 a loaf was the answer. I was amazed.