Does a new toilet use enough water to flush solids through older cast-iron drain lines that work fine with the original toilet?

Answer 1

Drainage is based on fixture units (FU'S) and a fixture unit is 1 cubic foot of water (7.48 gallons)

The older toilets used 3.6 GPF instead of the new 1.6 gallon per flush THUS the piping is not getting the same scouring action as they used to receive from the more gallon flow.

When I now take color video inspections I see spider webs and mosquitoes and lots of scale and soap scum and grease deposits on the internal piping walls as these lines are not flushed out properly.

Have you noticed more and more folks are coming down with bacteria related diseases that were un heard of before in America where we used to have properly designed systems.

The sewer systems now act as an incubator for west Niles E Coli and dangerous carcinogenic fumes that now linger in these systems.

Many of the stoppages are cause because the lack of volume leave solids behind especially on older piping systems that have settled and may have some slight back pitching problems.

To bad one cannot sue the politicians who arbitrarily pass laws with no regard to the publics health.