You’re not understanding what this reply means by cleaning the wastewater before putting it into the heat exchanger system. The residents will be flushing oil, grease, bleach, ammonia, draino, and other hazardous chemicals that will require a lot of water chemistry maintenance to prevent corrosion of the heat exchanger, piping, tubing, strainers, filters, pumps, valves, sensors, and other components. There is also the frequent cleaning of the strainers and changing of the filters that will require a lot of electricity, materials and labor. The cost of labor and materials will eventually cause the preventive maintenance on these systems to be neglected to improve the bottom line of building operations. The system may be run into the ground from a preventive maintenance perspective and eventually abandoned after it is no longer financially viable to be maintained and operated compared to more traditional heating systems. A consultant will probably come in after 20 years and recommend another heating system tied to government incentives, and an EPC will be contracted to install it for a premium with taxpayer money. Inflation and taxes will increase to pay for the incentives and middle class Americans will have to work harder for the same standard of living until corporate tax rates are increased and a millionaires tax is implemented. The US capitalist machine cycle is inevitable and it is up to us to use it to our benefit through our right to petition, organize, and vote.