Correct heads installation on a yacht.
Many yachts are at risk of sinking because of poorly installed heads. Without vented loops the toilet can backflood when the flapper valve or seal inthe plunger fails. The correct installation is shown below.
Other problems include leaking seals, water spray when the plunger is depressed, leaking seals or split diaphrams on Lavac toilets vacuum based toilets, stuck seacocks especially on the oulet, cracked bases, leaking holding tanks, blocked vents, calcified pipes, siezed macerators and poor worm drive clip connections.
Heavily calcified outlet pipe almost completely blocked.
Smell on this yacht was traced to this corroded fitting on a diaphragm pump from the holding tank.