How to Repair a Flanged Gate Valve

A flanged gate valve are normally used to easily turn the water supply on or off to an area from main water supply line or a water tank. When the gate valve for the water supply line gets bad in your home or leaks, you should repair it. This can be done by replacing some worn out or damaged parts and changing sealing rings and gaskets of the valve. The following procedure applies to all flanged gate valves:

Materials and Tools

  • Replacement parts
  • Packing rings
  • Wiping Rags
  • Gaskets
  • General Mechanical Tool Kit  
  • Lock washer
  • Solvent

Step 1- Turn off Water Supply

Turn off the water to the home from main supply valve.

Step 2- Disassembly of Gate Valve

Loosen the nut on the hand wheel attached to the stem. Remove the packing nut, gland spring and packing from the top of the bonnet. Dismantle the nuts, lock washers and cap screws from the valve body and bonnet. Use a mallet to tap the bonnet and make the sealing surface loose. Remove bonnet gasket and other attached parts from valve body. Take out the Allen screws and separate the discs from riser at the center. Remove the riser from stem. Unscrew the top stem from the bonnet bottom.

Step 3- Cleaning

Clean all the parts with solvent and wiping rags to remove dirt and dry them. Avoid the solvent getting contact with your skin or eyes.

Step4- Inspecting the Parts

Inspect  bonnet and valve body for any cracks, slashed mating surfaces, damaged threads and erosion. Check the stem for bend bent stem and worn out or stripped threads. Examine the sealing faces of discs and valve body. They should not have deep scratches or cracks.

Step 5 – Repairing the Valve

Replace the damaged or defective parts. Replace packing ring and all sealing components inside the valve.

Step 6 - Assembling the Gate Valve

Screw the stem into bottom of bonnet completely. Turn the stem back three full turns.  Keep the stem in this position. Hold the stem and screw the disc riser onto stem until the bottom of riser becomes flush with end of stem. Set the discs on riser and fix them with two Allen screws.

Prevent the stem from turning in bonnet, and turn discs as well as riser in the anticlockwise direction onto stem until top of discs contact bottom of bonnet. Place the gasket on the valve body. While holding stem in position, lower the bonnet and discs into the valve body. Align the discs with body, but do not rotate them more than 1/4 turn. Fix cap screws, lock washers  and nuts in valve body and bonnet.   Tighten all the nuts in a crosswise pattern evenly. Install the packing on stem and down into bonnet. Slide packing gland and gland spring on the stem. Fix and tighten the packing nut over stem. Place the hand wheel on stem and fix it with nut. The repair is done.

Step 7 - Turn the Main Supply On

Turn the main water supply on.