Well that would certainly do it. If your tap water isn't hard (lots of minerals) don't worry too hard about it. If the engine is due for a coolant service (every 5 years minimum) use it as an excuse to do so.

23 year old cars are going to require upkeep and maintenance. Part of life unfortunately.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)