I have a house built in 1929 and the cast supply pipe from the street to the house has never been replaced. I was inquiring about an inground sprinkler system and was told the volume of water was to low, likely because of years of build up within. My family and I have noticed this in day to day use (showers, toilets and washer, etc,...) and wondered if the gunk in the old pipes is able to be blown out, similar to a sprinkler system being prepped for winter. We have had other cast pipes replaced and saw that the pipes were choked by build up. Replacing the cast supply pipes isn't a financially viable option at this point. Please help.