Question:
I have a 1″ Febco model 860 reduced pressure principal assembly that is dripping from the relief valve and needs to be repaired. Can you give me some information on how to replace the diaphragm and seat disc in this relief valve?
Mark:
Before we get started, it is important to remember that discharge from the relief port does not necessarily indicate that there is a problem with the relief valve. Many times, the discharge is an indication of a failed No. 1 check valve. It is always a good idea to troubleshoot the assembly first to verify the problem. After you have determined that the relief valve needs service, go ahead and close the inlet and outlet shutoff valves and bleed off the water pressure.
Doug:
The relief valve on this unit is located on the bottom of the assembly. The access cover for the RV has what looks like a brass nut that is located in the center of the cover. Loosen this nut by loosening it ¼ turn counterclockwise. Then remove the relief valve cover bolts (2) and access the cover. The RV spring is separate from the RV module and is free when the cover is removed. This relief valve module is unique in that it is built into the access cover. The RV module has a large diaphragm that is visible and a smaller inner diaphragm that is attached to the access cover. To remove the RV module from the cover, simply unscrew and remove the brass nut on the cover. Grab the large diaphragm and module and pull away until the small diaphragm comes out through the hole in the cover.
Mark:
Now that the RV module is separated from the cover, you can disassemble the module and replace the rubber parts. The module is held together by a small Allen bolt. This bolt must be removed in order to replace the seat disc and both diaphragms. It is important to remember there are white plastic slip rings on either side of the small diaphragm that should be replaced. The relief valve seat is made of black plastic and located inside the body of the assembly. The RV seat simply slides into place and is sealed by a thin gasket. Do not to forget there is a small sensing line o-ring at the top of the RV cover.
Doug:
Once you’ve replaced the rubber parts of the module, you’re ready to reassemble the module into the RV cover. You must shape the small diaphragm so that it forms a “tulip” shape. It can then be inserted into the RV cover. Make sure the two white slip rings are in place (one on either side of the RV cover protecting the small diaphragm). A thin coat of food grade grease will help to hold them in position. Make sure the small diaphragm is not creased or folded under the slip ring. Replace the large brass nut into the cover, only hand tight. Turn the cover over to work on the large diaphragm. The large diaphragm must be formed so the bead on the outer edge is seated in the groove of the cover. Remember to place the RV spring between the module and the RV seat. The module and cover are now ready to be installed and bolted on the assembly.
