Our water heater is 11, so the wife decided we'd pre-emptively replace it, rather than wait for it to explode or piss all over the basement. The plumber actually showed up within 20 minutes to check out what we had, and sent his crew over right after lunch! Damn fast! So they got the heater all set up in about an hour. At that point my wife remembered that the owner said we should have them check our water pressure - he thought our town was okay, but if it's over 80psi, they'd need to put a reducer valve on the pipes and a header tank on the heater. Wish we'd remembered sooner. They had to completely finish the heater to turn the water on to check the pressure. 120 psi!! So they had to drain the heater and cut into the brand new pipes over the heater to install the tank. Then they went to install the valve on our main "in" pipe, to which he exclaimed "Aw jeez! How old is this?" The house is 73 years old. Those pipes are original. "*sigh* I have to replace this whole section." In the back of a closet! Three hours total time, $600 more than they'd thought before the pressure reading. It's never just the one thing.