To complete a backflow repair the water has to be shut down to release pressure from the line.
From installation to repair and troubleshooting, We are Atlanta Metro's Gate Valve Experts!
There are different brands of gate valves that are used in connection with backflow devices but most are set up in similar ways. Gate valves are broken down into two different types, OS&Y (Outside stem and yoke) and NRS (Non-rising stem).
OS&Y Gate Valve
OS&Y valves are what you will normally see connected to your backflow device inside the vault. The obvious way to tell the difference is whether there is a stem coming out above the hand wheel.
OS&Y valves operate by turning the hand wheel in a clockwise rotation to close and a counterclockwise rotation to open the valve. This moves the stem and wedge up and down, opening and closing the gate. The stem moves through the packing area and gland while in motion. This takes us into the very first thing that goes wrong on OS&Y valves.
The packing area contains a material that goes around the stem. It is compressed by the packing gland and is used to keep water from exiting from around the stem. This packing must be replaced periodically because it is exposed to the water inside of the valve as the valve is opened and closed. The easiest way to tell when the packing has gone bad is to check for water leaking from around the stem. It is possible to replace the packing without shutting off any water.
NRS Gate Valve
Non-rising stem gate valves are normally used underground and are accessible through a small cylindrical pipe that sits on top of the valve and goes to the top of the ground. This allows a technician to open and close the valve with a special square head key. NRS valves can be used inside vaults and on other applications but in our service area they are mostly used on underground pipe that is not accessible unless the area is excavated.
One of the most common deficiencies on these valves is the stem gets stuck within the housing and cannot be turned. This means the valve cannot be opened or closed. This occurs when the valve is not exercised frequently (opened and closed).
If the valve is accessible within a vault this repair can be completed more cost efficient than replacing the valve. If it is not accessible the area will have to be excavated to complete any repairs.