Push-pull valves
1. The most common type of backwash valves in use — push-pull valves — have been around for years. They can be found on sand and DE filters, and a number of manufacturers offer them.
For most DE models, the valve is down for filter and up for backwash. On most sand varieties, it’s the opposite: up for filter and down for backwash. Most manufacturers have changed their push-pull valves from brass to plastic (PVC and ABS) — O-rings for an old brass valve may not fit the new plastic valves — but the basic repair procedures for these valves has stayed about the same.
The stem of the push-pull valve has four O-rings on it. The two piston O-rings keep the water flowing in the right direction. The cap O-ring and stem O-ring keep water from leaking out from under the cap and around the stem. All four should be replaced when rebuilding. As the valve gets old, it can be difficult to remove the cap by hand. When this happens, a strap wrench or tongue-and-groove pliers, gently applied, may be the only way to open the valve.
2. Pull the stem out of the valve body.
3. Use a small-blade screwdriver or an O-ring pick to remove the O-rings from the stem. If the stem is metal, use a small piece of sanding cloth to clean the groove before rolling a new O-ring into place. Clean the top of the stem to help it slide more easily.
4. Apply a layer of lube to the O-rings and put the stem back into the backwash body.
5. When reassembling the valve, always follow the manufacturer’s instructions and “hand tighten only.”