Hydro-Mechanical Installations
A hydro-mechanical interceptor separates grease in a smaller box, usually under a sink or on the kitchen floor. Flow control and internal baffles do the work that a large outdoor tank does with time and volume.
The smaller box fills faster. It needs more frequent cleaning than an in-ground gravity tank. Skipping that cleaning sends grease down the line.
Because the box is small, the cleaning interval is short. The service is still pumping, scraping the interior walls, wash-out, and a check of the inlet and outlet. Skipping that visit is how a floor box sends grease down the line.
Installation details that decide whether it works
A hydro-mechanical interceptor is a compact box. It uses baffles and, usually, a flow-control device so a rush of water does not blow grease out the outlet. Installation is the moment those parts are set correctly or set wrong for the life of the kitchen. The flow control belongs on the inlet side, where the manufacturer drew it. Leave it out, or install it backward, and the box is just a small tank with no time to separate anything. An air intake on that control has to stay open. A control buried above a ceiling that nobody can reach will clog, and the sinks will slow down.
The box has to stay vented and accessible. A hydro-mechanical unit under a sink still needs clearance for the lid. If the lid cannot come off, it cannot be pumped. Dish machines and food grinders are often forbidden on the same inlet, because a grinder fills the box with solids and a dish machine's detergents emulsify the fat. The manufacturer's instructions and the local plumbing code both say so. A field change that adds a grinder later defeats the installation.
These units are rated by flow, in gallons per minute, not by the loose volume of a gravity tank. Matching the rating to the fixtures is the sizing step. A box that is too small for a new prep program fills in days. The cleaning method does not change with the rating. GREASE.ORG still pumps it out, scrapes it, washes it, and checks the inlet and outlet. The interval is simply shorter than the interval for an in-ground tank.
If the box smells or the sink rises a week after a pump-out, suspect the flow control, a missing baffle, or a new fixture before you suspect the pumping. Installation is plumbing. Pumping is the repeating service. A kitchen needs the box installed as designed, and then needs it emptied before the grease reaches the outlet.