Before replacing the entire resevoir, check a couple things. Make sure that the braided hoses aren't cracked, broken or pinched in the hood hinge (can happen). If the hoses are all fine then check the washer pump(s) grommet(s). The rubber grommets do tend to break down over time and will leak profusely. The pumps are mounted low on the backside of the resevoir. Also check to make sure the pump(s) are pressed all the way down, if they aren't the grommet won't seal.
Depending on the year of your car your resevoir could be heated by coolant lines, or electrically.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.