Wilkins 975xl

Today we are looking at the Wilkins 975xl

Wilkins Zurn published some Installation, Testing and Maintenance Instructions for the device and they are as follows:  wilkins 975xl

If you didn’t make it through the whole thing here are the important parts regarding maintenance:

All Model 975XL Reduced Pressure Principle Backflow Preventers must be inspected and maintained by licensed personnel at least once a year or more frequently as specified by local codes. Replacement of worn or damaged parts must only be made with genuine “ZURN WILKINS” parts. The ZURN WILKINS Certificate of Limited Warranty provides that failure to do so “…releases ZURN WILKINS of any liability that it might otherwise have withrespect to that device.” Such failure could also result in an im properly functioning device.

The Model 975XL Reduced Pressure Principle Assemblies should be thoroughly flushed after backflow conditions occur to preventany type of corrosive deterioration to its components. Failure to do so could result in malfunction of the device.


1. Clean all parts thoroughly with water after disassembly.

2. Carefully inspect rubber seal rings, diaphragms and o-rings for damage.

3. Test unit after reassembly for proper operation (see “Testing Procedures”).


1. Close inlet and outlet shut-off valves.

2. Open No. 2, No. 3 and No. 4 test cocks to release pressure from valve.

3. Unscrew check valve covers using appropriate size wrench (CAUTION: Cover is spring loaded). To avoid injury, hold cover down firmly with one hand while unscrewing.

4. Remove check valve cover, spring and poppet assembly.

5. Inspect the rubber seal ring for cuts or embedded debris. To remove seal ring, remove screw and seal ring retainer. If the reverse side of the seal ring is unused, it is possible to invert the seal ring. This would be considered a temporary solution to fixing a fouled check and should be replaced with a new seal ring as soon as possible.

6. Inspect valve cavity and seating area. Remove any debris.

7. If installed with removable seat, unscrew seat from body andreplace with new seat and lightly grease o-ring.*

8. Reverse the above procedures to reinstall check valve assembly. Care should be taken to make sure the heavy spring is installed in the No. 1 check valve. For the 3/4″-1″ 975XLSE the No. 2 poppet has a cupped seal retainer. For the 1 1/4″-2″ 975XLSE the No. 1 seat has a taller seat profile than the No. 2 seat.


1. Remove relief valve cover bolts and cover. Gently pull on dia phragm to remove the cartridge assembly.

2. Inspect seal ring for cuts and embedded debris. Turn over or replace if required.

3. Disassemble cartridge by unscrewing relief valve retaining screw.

4. Inspect diaphragm and o-rings for damage. Replace required parts and apply a light coat of grease to plunger o-ring.

5. Carefully reassemble cartridge assembly.

6. Inspect relief valve seat for wear on seating surface. If damaged, replace seat and seat o-ring.*

7. Insert cartridge assembly into relief valve body.

8. Replace relief valve cover and cover bolts.

9. Place device in service and test per “TESTING PROCEDURES”.

*For seat removal assistance, consult factory.