About the  Flout®

A Single Flout®

Simple, reliable dosing

Rissy Plastics invented the Flout® aka Floating Outlet® Dosing System in 1992. Thousands of units are in service worldwide. As a direct replacement for the common bell siphon, with much simpler installation and more reliable operation, the Flout® offers the Professional Waste Water System Designer new flexibility in the system design. Flow management is easier to do with a Flout®!


A chamber of sufficient dimensions to contain the required dose has an upper inlet and a lower outlet, usually at floor level. No plumbing extends below the floor. The outlet diameter is usually 3 inches but may be 4 inches, 2 inches, or as small as 1 inch. 

Basic Flout Demonstration

Watch the First Flout work...

The Flout® Cycle

1. The Flout® is free floating, hinging on the flexible connector as the chamber fills.

2.  When the Flout reaches maximum, liquid spills in, sinking it and opening the outlet to flow. 

3. As the liquid  drains down to the top of the Flout, it empties and begins to float again, closing the outlet, and begins a new cycle.

A box shaped vessel floats on the surface of the liquid in the chamber. There is an opening in the upper side of the vessel and a ballast weight is attached. A length of pipe extends far into the vessel, through the side, and attaches to a special flexible connector the same diameter as the pipe. The other end of the connector is connected to the outlet, usually via a tee fitting with a vent extending above the maximum liquid level. 

The flexible connector acts as a hinge, allowing the vessel to float ever higher as the chamber fills. When the vessel can float no higher, liquid spills into the vessel, forcing it to sink to the floor, allowing the liquid to flow through the outlet. When the liquid level drops to the top of the vessel, flow stops when the vessel drains and re-floats in the remaining liquid. 

single outlet Flout  may serve more than one disposal area with the use of distribution boxes. A multiple outlet Flout provides individual outlets for each section of the disposal area. Outlets may be combined for larger flows or incrementally combined for precise flow splitting.

Pairs of Flouts may be alternated  and two or more may be sequenced.

Failed siphons  are readily replaced with Flouts.

This system makes gravity dosing easy to implement with it's simple design, ease of installation, and trouble free operation. Unlike a siphon, the Flout does not need a downward projecting trap. The trap makes for difficult installation in the field or in the precast plant. And a Flout never needs and can never loose a prime.

The best way to understand how it works is to watch a video of the first Flout installed in 1992. 

Let's see it.

Flout and Floating Outlet are Registered Trademarks of Rissy Plastics, llc

US Patent No : 5290434

Rissy Plastics, LLC, 350 Cedar Lane, Torrington, CT 06790 USA, +1-860-482-1645
     Call or text  Jim directly  at +1-860-459-9995 or email TANXRUS@aol.com         ©2023 Rissy Plastics, LLC