商榷一下

The four requirements listed above are incorrect. Hall case normally applies only in product liability mass torts cases which the plaintiffs cannot identify the producer of the defected product. But the whole industry produces the almost identical defected product which causes the injury. For instance, some drug causes serious side effects after many years. At that time, consumers cannot prove which company produces the drug they took. So the court held that if the plaintiffs can satisfy those four requirements, the whole industry whould be responsible for the damage.
Clearly this is not the case here. In this case, the plaintiff can identify the landlord and sue him for negligence. Normally, plaintiff in this situation would ask the housing department to inspect the house. If there shows the lead pollution, the plaintiff may sue under negligent per se. Also the plaintiff can also sue the producer of those water pipes under product liability. All these are very fact sentitive and who is the deep pocket.