Philadelphia Water Main Service Line - Is it illegal?

[Jae Hee Hwang]

Hello! I just bought my first house in Philadelphia. The house has lead main water service line, and my property management (who also does work in the house for a commission) says that it's illegal and I should get it replaced to copper, which would cost $4000. Is it illegal? It seems that most old houses are still using lead pipe and my neighbors haven't replaced them. Some plumbers I talked to also said they wouldn't do anything about it. 

I would like to make the water safe for my prospective tenants, and I definitely don't want them to get lead poisoning. I would like to make the water safe for them, but I'm just not sure if the water service line replacement is necessary. The property management also says that they pulled a permit for the issue and it cost $1200, and I'm surprised that the permit would cost that much. 

Do any other Philadelphia investors have experience with lead water service line? Did you replace them or put a filtration system? It would greatly help me if you can share your experience. Thank you so much!

P.S: Philadelphia's water department website doesn't mention anything about the legality of it either. It says alternatives are water filtration system, etc, which would cost a lot less than $4000.