The U.S. Environmental Protection Agency’s (EPA) Water Infrastructure Resiliency and Finance Center, in collaboration with the...
Automatic Backwater Valve Eliminates Backflow During Heavy Rainfalls.
The main problem occurred at a church during heavy rainfalls, when the main sewer line would routinely back up through the basement floor drains into the nursery.
After investigating the situation, the city determined there was insufficient “fall” in the three lines running from the church into the main line to protect it from back flow. A contributing problem was that the old flapper valve which had formerly been protecting the church had rusted severely, allowing water to get into the basement nursery.
The Flood-Gate valve was chosen as the solution, and its stainless steel knife gate was installed in a 20-foot-deep concrete pit.
According to the city, the Flood-Gate has been closing automatically when needed, providing positive shut off during reported back flow conditions. The nursery in particular and the church in general have been reliably protected from a reoccurrence of backwater influx.
In all of its installations, this backwater valve has been successful in protecting homes and business from flood damage along a total of 2,700 miles of sewer main for more than 100,000 customers. When back flow conditions occur, the Flood-Gate closes automatically — providing positive shut off and property protection; no one needs to activate the valve during back flow conditions.
A sewerage back flow into the building/house will happen if a stoppage or similar problem in the municipal/street sewer or septic system occurs causing the water level to rise above the top of the building/house drain. It is under these conditions that the Flood-Gate works. As the sewerage back flow occurs, the trapped air in the sewerage line is forced into the expansion chamber through a port in the valve. As the expansion chamber fills with air and expands, the knife gate rises until the 4-in. or 6-in. drainage opening is completely sealed off. This usually occurs with a 9-in. head of water for a 4-in. Flood-Gate valve, and 14-in. head of water for a 6-in. valve.
Once a complete closure is obtained in the valve, all back flow is prevented from entering the building or structure. When the back flow subsides and the water level returns to normal, the counterweight on top of the expansion chamber forces the trapped air out of the chamber and into the drainage line, allowing the knife gate to lower to a full open position. Now the Flood-Gate is ready to guard against future back flow situations.
The Flood-Gate is designed to work in residential basements, commercial and institutional buildings, in industrial applications, and restaurants. Depending on individual circumstances, the Flood-Gate can be installed in a ventilated pit in the horizontal drain line between the building and the sewer main. Although this provides complete protection from flooding, all of the plumbing fixtures in the building will be out of service once the Flood-Gate is activated.
An alternative installation is to locate the Flood-Gate where only the fixtures installed below grade (as in a basement) are connected on the upstream side of the valve. All fixtures installed above grade are connected on the downstream (sewer) side of the valve. This allows continued use of the above grade fixtures, while protecting below grade areas from flooding.
Each Flood-Gate Backwater Valve has been thoroughly inspected and tested to a 45-ft.head, or 19.3 psi, without any visible signs of leakage or seepage. The Flood-Gate conforms to requirements per ASME A112.14.1-1975 for backwater valves; has a certificate of compliance from CSA, reference T.I.L. No. MSE 30; and is IAMPO listed, File No. 3758 (4-in. only). Debris does not get caught since the Flood-Gate is a full port valve and it does not have a flapper that can be obstructed.
The Flood-Gate Automatic In-line Backwater Valve is furnished with 4-in. or 6-in. no-hub connections. The unit is designed to be a full port valve and provided for in-line installation. It is constructed with a duco coated cast iron housing, 14 gauge, type 304 stainless steel knife gate with neoprene O-ring seals, flexible PVC expansion chamber with a polyethylene cover and cast iron counterweight. Options include Flood-Gate alarm, pit, and steel pit cover.
In most of its installations, the Flood-Gate was purchased on the principle of low maintenance for the owner and ease of installation for the plumbing contractor. It has been three years since the first Flood-Gate was installed, and there have been no reported problems.